Soil science
Fatemeh Bibi Shahabi; Reza Khorasani; zahra gheshlaghi
Abstract
Introduction:
This study examined the influence of glutathione on iron availability in calcareous soils and its effect on the iron availability from various sources for peanut plants. Calcareous soils, prevalent in many regions, challenge nutrient availability, particularly for micronutrients such as ...
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Introduction:
This study examined the influence of glutathione on iron availability in calcareous soils and its effect on the iron availability from various sources for peanut plants. Calcareous soils, prevalent in many regions, challenge nutrient availability, particularly for micronutrients such as iron, manganese, and zinc, owing to their high pH levels. Despite adequate iron levels in these soils, plant accessibility remains restricted, often resulting in iron deficiency symptoms, such as chlorosis, due to impaired chlorophyll synthesis. Various strategies, including the development of resistant cultivars, organic amendments, and mineral or chelated iron fertilizers, have been explored to mitigate Fe deficiency. Chelated iron fertilizers, especially iron sequestration (EDDHA) agents, are commonly used in calcareous soils to enhance iron availability in plants. However, their environmental impact and cost-effectiveness are concerns, prompting interest in alternatives such as iron oxides, which are cost-effective and environmentally friendly. Research suggests that iron oxides, particularly magnetite nanoparticles, support plant growth and enhance the availability of iron. Additionally, growth stimulants, such as glutathione (a tripeptide with antioxidant properties), have been investigated for their potential to alleviate iron deficiency. Glutathione not only boosts plant defense mechanisms but also improves reactive oxygen species availability. Recent studies have shown that the foliar application of glutathione in iron-deficient plants can significantly increase total iron uptake and enhance photosynthesis. This study aimed to investigate the effects of glutathione on iron bioavailability from various iron sources and growth parameters in peanuts cultivated in calcareous soils.
Materials and Methods (331 words):
The experiment was conducted in a greenhouse at the Agricultural Research Center of Ferdowsi University of Mashha and, employed a completely randomized factorial design with three replications. The factors were iron sources (control, iron sequestration (EDDHA), iron oxide, and iron filings) and glutathione foliar application (0, 1, and 2 mM, four times per growth season: 29, 38, 42, and 48, after planting). Soil was collected from a farm, and some of its physical and chemical properties were analyzed using conventional methods. Macronutrients were added at the recommended dosage to minimise interference with iron treatment. The iron levels were 0 and 50, 1.37, and 0.108 mg/kg for sequestration, iron oxide, and iron filings, respectively. Glutathione foliar treatments were applied at four growth stages (29, 38, 42, 48 days after planting) in concentrations of 0, 1, and 2 mM. The plants were grown in pots with soil moisture maintained at the field capacity. After 66 days, the plants were harvested, and parameters such as dry shoot weight, total iron uptake, and nitrogen were measured. The iron content in plants was determined using atomic absorption spectroscopy, and nitrogen was quantified using the Kjeldahl method. Statistical analyses were conducted using SAS software, and mean comparisons were performed using Duncan's test at the 5% significance level. This study aimed to assess the effects of different iron sources and glutathione on iron bioavailability and plant growth in calcareous soil conditions.
Results and Discussion
The study revealed that glutathione, either alone or in combination with iron sources, notably improved peanut plant growth and iron uptake. Iron sequestration (EDDHA) was the most effective treatment, significantly increasing dry shoot weight, particularly when combined with 2 mM glutathione. The combination of glutathione and iron treatment substantially boosted total iron uptake in both the shoots and roots of peanut plants. Notably, iron sequestration (EDDHA) with glutathione resulted in a 20% increase in shoot iron uptake and a 34.3% increase in shoot nitrogen uptake compared to glutathione treatment alone. Glutathione application also enhanced iron filings, leading to a 55.6% increase in root iron uptake by shoots and a 50.6% increase in iron concentration in shoots, as extracted by phenanthroline. The results indicated that glutathione improves and facilitates iron translocation from the roots to the shoots. Iron filings, a cost-effective iron source, showed significant results when paired with glutathione, enhancing both shoot dry weight and iron uptake. This synergy between glutathione and iron treatments suggests that iron sequestration (EDDHA) is more effective when combined with glutathione, resulting in alleviating deficiency symptoms of iron, such as chlorosis, and promoting overall growth.
Conclusion):
This study underscores the positive impact of glutathione on iron availability and growth in peanut plants grown in calcareous soils. Appliying glutathione significantly increased iron uptake in both shoots and roots, nitrogen uptake, and plant biomass. Iron sequestration (EDDHA), combined with glutathione, emerged as the most effective treatment, improving shoot iron and nitrogen uptake by 20% and 34.3%, respectively. Additionally, glutathione enhanced the efficacy of iron filings, an economical iron source, suggesting its potential as an alternative to expensive iron fertilizers. Glutathione application also reduced chlorosis and improved iron translocation from roots to shoots, supporting its role in enhancing iron nutrition in crops grown in iron-deficient soils. This study offers insights into the role of glutathione in managing iron deficiency stress and recommends further exploration of optimal application rates and effects on diverse crops and soil conditions.
Soil science
Mahsa Hasanpour Kashani; Shokrollah Asghari
Abstract
Introduction Soil available water (SAW) is defined as the difference between field capacity (FC) and permanent wilting point (PWP). FC is the amount of soil water content held by the soil after the gravitational water was drained from the soil. PWP is defined as a minimum water content of a soil which ...
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Introduction Soil available water (SAW) is defined as the difference between field capacity (FC) and permanent wilting point (PWP). FC is the amount of soil water content held by the soil after the gravitational water was drained from the soil. PWP is defined as a minimum water content of a soil which is needed for the crop survival and if the water content decreases lower than PWP, a plant wilts and can no longer recover itself. The direct measurement of FC and PWP soil water contents is very costly and time consuming; Therefore, it is useful the use of different intelligent models such as neuro-fuzzy (NF), gene expression programming (GEP) and random forest (RF) to estimate FC, PWP and SAW through easily accessible and low-cost soil characteristics. The objectives of this research were: (1) to obtain NF, GEP and RF models for estimating SAW from the easily accessible soil variables in the cultivated lands of Ardabil plain (2) to compare the accuracy of the mentioned models in estimating SAW using the coefficient of determination (R2), root mean square error (RMSE), mean error (ME) and Nash-Sutcliffe coefficient (NS) criteria.
Materials and methods The measured data from 102 soil samples taken from 0-10 cm soil depth of the cultivated lands of Ardabil plain, northwest of Iran, were used in this study. Sand, clay, mean geometric diameter (dg) and geometric standard deviation (σg) of soil particles, bulk density (BD) and organic carbon (OC) were introduced as input variables to the applied three intelligent models for estimating soil available water (SAW). Data randomly were divided in two series as 82 data for training and 20 data for testing of models. In all models, six different input variables combinations were used; SPSS 22 software with stepwise method was applied to select the input variables. MATLAB, Gene Xpro Tools 4.0 and Weka softwares were used to derive neuro-fuzzy (NF), gene expression programming (GEP) and random forest (RF) models, respectively. One of the important steps using NF method is selecting the appropriate membership functions (MFs) and its numbers. Based on a trial and error procedure, 3 numbers of MFs and 50 to 100 optimum replications were found for the NF modeling. Also, the input MFs were chosen as “triangular”, “trapezoid”, “generalized bell” and “pi” and the output MF was selected as “constant”. A set of optimal parameters were chosen before developing a best GEP model. The number of chromosomes and genes, head size and linking function were selected by the trial and error method, and they are 30, 3, 8, and +, respectively. The rates of genetic operators were chosen according to literature studies. Various tree numbers were analyzed for choosing the best random forest (RF) method. Increasing the tree numbers beyond 100 made lower variations in the average squared error values for the SAW estimation cases. The accuracy of NF, GEP and RF models in estimating SAW was evaluated by coefficient of determination (R2), root mean square error (RMSE), mean error (ME) and Nash-Sutcliffe coefficient (NS) statistics.
Results and discussion The studied soils had loam (n= 53), clay loam (n= 26), sandy loam (n= 15), silt loam (n= 6) and clay (n= 2) textural classes. The values of sand (24.40 to 68.00 %), clay (3.80 to 42.90 %), dg (0.02 to 0.26 mm), σg (7.48 to 19.41), BD (1.04 to 1.70 g cm-3), OC (0.31 to 1.52 %) and SAW (5.10 to 25.10 % g g-1) indicated good variations in the soils of studied region. There were found significant correlations between SAW with BD (r= - 0.59**), clay (r= 0.56**), OC (r= 0.45**) and sand (r= - 0.44**). NF, GEP and RF models were applied to estimate SAW using six different combinations of input soil variables (sand, clay, dg, σg, BD and OC). The results of the best NF, GEP and RF models indicated that the most appropriate input variables to predict SAW were OC and BD. The values of R2, RMSE, ME and NS criteria were obtained equal 0.73, 2.51 % g g-1, 0.09 % g g-1and 0.71, and 0.76, 3.10 % g g-1, - 1.41 % g g-1 and 0.56, 0.68, 3.30 % g g-1, - 1.45 % g g-1, 0.50 for the best NF, GEP and RF models in the testing data set, respectively. Numerous investigations also showed that there are significant negative correlation between SAW with BD and sand and positive correlation between SAW with OC and clay.
Conclusion The results of three investigated intelligent models showed that OC and BD were the most important and readily available soil variables to predict soil available water (SAW) in the studied area. According to the lowest values of RMSE and the highest values of NS, the accuracy of NF models to estimate SAW was more than GEP and RF models. RF approach gave the worst estimates for SAW in this research.
Soil science
Fereydun Nourgholipour; maryam mohammady; Hossein Mir Seyed Hosseini; Reza Soleimani
Abstract
Introduction
The cultivation area of canola (Brassica napus L.) has increased globally due to its climatic adaptability and its different growing season compared to other oilseeds. Additionally, its ability to be cropped in rotation with other plants, such as cereals, has contributed to its popularity. ...
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Introduction
The cultivation area of canola (Brassica napus L.) has increased globally due to its climatic adaptability and its different growing season compared to other oilseeds. Additionally, its ability to be cropped in rotation with other plants, such as cereals, has contributed to its popularity. Canola has the largest cultivated area among oilseed crops in Iran. Proper consumption of nutrients is crucial for improving growth and increasing seed yield in canola plants. The use of sulfur as an essential nutrient, along with selenium in low concentrations as a beneficial nutrient, plays a significant role in enhancing plant tolerance to environmental stresses. Sulfur and selenium are both elements of group 16 of the periodic elements table and have similar physical and chemical properties, and it is believed that selenium utilizes the same pathways for sulfur immobilization and uptake in plants. Given the similarity of selenium to sulfur, sulfur metabolic pathways are shared, so the effect of selenium on growth is expected to be largely influenced by sulfur nutrition. This study aims to investigate the effects of sulfur and selenium application on nutrient absorption and their interaction on canola plant growth indices.
Materials and Methods
The experiment was conducted in greenhouse conditions as a factorial in a completely randomized design with 12 treatments and three replications. For cultivation, plastic pots with a diameter of 20 cm were utilized. Four kilograms of sieved soil were added to each pot. 100 mg kg-1 of nitrogen from urea source was applied in the pre-planting stage and 100 mg of nitrogen was applied in two stages (after establishment on day 21 and then in the stem elongation before flowering stage). Triple superphosphate at a rate of 80 mg of phosphorus per kg of soil was added to the pots in powder form before planting and iron at a rate of 5 mg kg-1 in the form of iron chelate solution was added to the pots. The experimental treatments included elemental sulfur fertilizer at two levels of zero and 20 mg kg-1 (inoculated with Thiobacillus inoculum), two sources of selenium fertilizer (sodium selenate and selenite) at three levels of zero, 30, and 60 μg/kg in soil form before planting. The amount of sulfur and selenium available in the soil before planting was 3.8 and 0.025 mg/kg, respectively. The cultivated canola variety was Dalgan and grown in greenhouse conditions for 5 months. This cultivar is open-pollinated. The sulfur was in powder form with a purity of 99%, which was added to the soil of the sulfur-containing treatments, along with Thiobacillus inoculum (with a population of 1×108 cells per ml) two weeks before planting. After the seed growth and maturation period (5 months), at the final stage of growth (physiological maturity with a two-digit growth code of 80), the seed components were separated from the aerial parts. The dry weight of the seed and the aerial parts of the plant were weighed separately.
Results and Discussion
Sulfur application significantly increased shoot dry weight, root dry weight, leaf area, and canola grain weight compared to conditions without sulfur application (48.8% increase in shoot weight, 28.1% in root weight, 15.7% in leaf area, and 51.3% increase in grain weight). Grain weight had a correlation of 0.94** with grain sulfur uptake and 0.9** with shoot sulfur uptake. Therefore, the growth characteristics of roots, shoots, and sulfur concentration in shoots and seeds have a significant impact on grain weight. Application of selenium from selenate source resulted in higher selenium absorption in shoots and canola grain compared to selenite source. In grain, sulfur application increased selenium absorption from both sources. Grain sulfur uptake had a correlation of -0.42** with seed selenium concentration, 0.94** with seed weight, 0.86** with shoot sulfur concentration, -0.43* with shoot selenium concentration, 0.87** with shoot sulfur uptake, 0.7** with shoot weight, 0.69** with leaf area, and 0.83** with root weight. The highest grain selenium concentration was observed at the rate of 60 μg kg-1 from selenate source (0.48 mg kg-1). If increasing the selenium concentration of the grain is desired for enrichment purposes (from 0.12 μg g-1 in the sulfur-free and selenium-free treatments), a sulfur treatment of 20 mg kg-1 and a selenate content of 60 μg kg-1 could be considered to achieve a concentration of 0.42 μg g-1. This is because the grain weight of this treatment (3.87 g pot-1) was closest to the high levels of grain weight in the sulfur treatment of 20 mg kg-1 and selenium-free condition (4.32 g pot-1).
Conclusion
Grain selenium concentrations of 0.10-0.11 mg kg-1 and sulfur concentrations of 0.325-0.33% produced suitable canola yield. The highest canola grain weight was obtained with a concentration of 19.86 mg kg-1 sulfur and 0.0267 mg kg-1 selenium in the soil.
Soil science
Yahya Kooch; Mahin Fooladi Doghazlo; Katayoun Haghverdi
Abstract
Abstract
Vegetation, as a key factor in ecosystems, has significant impacts on soil properties through multiple ecological processes. Vegetative covers contribute to soil structure and composition by stabilizing organic matter, controlling erosion, regulating moisture, facilitating nutrient cycling, ...
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Abstract
Vegetation, as a key factor in ecosystems, has significant impacts on soil properties through multiple ecological processes. Vegetative covers contribute to soil structure and composition by stabilizing organic matter, controlling erosion, regulating moisture, facilitating nutrient cycling, and fostering microbial activity. While extensive research has elucidated the effects of various vegetation types on the physical and chemical properties of soil, the biological attributes of soil under different vegetation covers, particularly tree and shrub species, remain underexplored. This study aims to comprehensively evaluate the characteristics of the organic and mineral soil layers in areas dominated by Quercus macranthera tree cover, Crataegus microphylla shrub cover, Berberis integerrima shrub cover, and a mixed Crataegus microphylla and Berberis integerrima shrub cover in Rudbar County, Guilan Province, Iran. By examining these diverse vegetation types, the study seeks to elucidate their differential impacts on soil health and ecosystem functionality, providing insights for sustainable land management.
Materials and Methods
To investigate the influence of vegetation cover on soil properties, a rigorous site selection process was employed. Following preliminary field assessments, study areas were chosen to ensure continuity of vegetation cover and minimal variations in topographic factors, including elevation above sea level, slope gradient, and aspect. This approach minimized confounding variables, allowing for accurate comparisons across vegetation types. In each habitat, two 100 m × 100 m plots were implemented, with a minimum separation of 500 meters to account for spatial variability. Within each one-hectare plot, five soil samples (30 cm × 30 cm surface area, 10 cm depth) were collected from the organic and mineral layers at the four corners and the center of the plot. In total, 10 litter samples and 10 soil samples were collected from each vegetation type and transported to the laboratory for detailed analysis. Laboratory assays evaluated a suite of physical, chemical, and biological parameters, including soil aggregate stability, nutrient content, enzymatic activities, and microbial community dynamics, to provide a comprehensive understanding of soil responses to vegetation cover.
Results and Discussion
The findings revealed marked differences in soil properties across the studied vegetation types. The Q. macranthera tree cover exhibited the highest amount of essential nutrients in the organic layer, including nitrogen, phosphorus, potassium, calcium, and magnesium, reflecting its capacity to enhance nutrient cycling. In contrast, the B. integerrima shrub cover consistently showed the lowest nutrient amounts, suggesting limited contributions to soil fertility. Analysis of physical and chemical soil properties further underscored these disparities. The Q. macranthera cover demonstrated superior soil aggregate stability, higher clay content, increased coarse and fine aggregate percentages, optimal pH, and elevated levels of total nitrogen, ammonium, nitrate, phosphorus, potassium, calcium, and fine root biomass. Enzymatic activities, including urease, acid phosphatase, arylsulfatase, and invertase, were also significantly higher under Q. macranthera, indicating robust microbial and biochemical processes. Conversely, B. integerrima cover recorded the lowest values for these parameters, highlighting its limited impact on soil structure and function. Particulate and dissolved organic nitrogen levels were similarly highest under Q. macranthera, reinforcing its role in organic matter dynamics. Biological soil properties mirrored these trends. The Q. macranthera cover supported the highest densities of soil microfauna, including Acarina, Collembola, and nematodes, as well as abundant protozoa, fungal, and bacterial populations. Metrics of microbial activity, such as basal respiration, substrate-induced respiration, microbial biomass nitrogen, and microbial biomass phosphorus, were also maximized under this tree cover, reflecting a thriving soil microbial community. In contrast, B. integerrima cover exhibited the lowest values for these biological indicators, suggesting a less supportive environment for soil biota. Temporal analysis of carbon mineralization revealed significant variations at weeks 2, 4, 5, 8, and 12, with no notable changes at weeks 1 and 17. The highest carbon mineralization rates were observed under Q. macranthera, while B. integerrima showed the lowest. Nitrogen mineralization followed a similar pattern, with significant changes on days 7, 14, 21, 28, and 35, and the highest rates under Q. macranthera. These results collectively indicate that vegetation type, combined with topographic factors like elevation, significantly shapes the physical, chemical, and biological characteristics of soil in Rudbar County.
Conclusion
This study demonstrates that Q. macranthera tree cover significantly enhances soil quality compared to C. microphylla, B. integerrima, and their mixed shrub covers. The superior physical, chemical, and biological properties observed under Q. macranthera highlight its critical role in fostering soil microbial communities, improving nutrient cycling, and maintaining soil fertility. Enhanced carbon and nitrogen mineralization rates further underscore the importance of this tree species in driving biogeochemical processes essential for ecosystem health. These findings have important implications for land-use planning, forest management, and ecological restoration in Rudbar County. By prioritizing Q. macranthera in reforestation and conservation strategies, land managers can optimize soil productivity and ecosystem resilience. Future research should focus on long-term monitoring of these soil-vegetation interactions and explore additional environmental factors, such as climate and land-use history, to further refine management practices. The integration of such data will support the development of sustainable strategies that balance ecological health with agricultural and forestry objectives, ensuring the long-term vitality of Rudbar County’s ecosystems.
Soil science
Seyed Hamidehi Mousavi Dizkouhi; Mojtaba Barani Motlagh; Esmaeil Dordipour; Elham Malekzadeh; Fardin Sadeghzadeh; mahmmod ghasem nezhad
Abstract
Introduction
The olive tree (Olea europaea L.) is one of the most significant and ancient cultivated plants in the Mediterranean region, prized for its edible fruit and high-quality oil. However, the increasing scale of olive oil production has led to the accumulation of large quantities of solid waste, ...
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Introduction
The olive tree (Olea europaea L.) is one of the most significant and ancient cultivated plants in the Mediterranean region, prized for its edible fruit and high-quality oil. However, the increasing scale of olive oil production has led to the accumulation of large quantities of solid waste, particularly olive solid pomace (OSP), which poses considerable environmental challenges due to its high organic load and phytotoxic components. Sustainable management and valorization of this waste are crucial for reducing environmental risks and improving the circular economy in agricultural systems. This study aimed to evaluate the effects of compost and vermicompost derived from OSP, both in enriched and non-enriched forms, on the yield of olive fruit and the quality characteristics of the resulting olive oil. To this end, a field experiment was conducted during the 2018 growing season in a traditional olive orchard located in Rudbar, Gilan Province, Iran. The experiment was carried out using a randomized complete block design (RCBD) with 12 treatments and three replications on the ‘Arbequina’ cultivar, a well-known olive variety cultivated for its high oil content and quality.
Materials and Methods
Compost and vermicompost were first produced from olive solid pomace. After analyzing their basic physicochemical properties, several treatments were biologically enriched using plant growth-promoting rhizobacteria (PGPR), including Bacillus megaterium (phosphorus-solubilizing), Azotobacter chroococcum (nitrogen-fixing), and Thiobacillus thioparus (sulfur-oxidizing). Additional treatments were chemically enriched by incorporating 1 kg each of urea (as a nitrogen source), triple superphosphate (as a phosphorus source), and elemental sulfur at a rate of 1% by weight. The experimental treatments included: raw olive pomace, unenriched compost, chemically enriched compost, biologically enriched compost, unenriched vermicompost, chemically enriched vermicompost, biologically enriched vermicompost, a full NPK fertilizer treatment, a manure-only treatment (10 kg of animal manure), and a no-fertilizer control. All olive waste-based amendments were applied at 3% w/w. NPK fertilizers included urea (750 g in three split applications), triple superphosphate (250 g), and potassium sulfate (750 g). Micronutrients such as magnesium sulfate, manganese, iron, zinc, copper, boric acid, and elemental sulfur were applied based on soil test recommendations. Uniform horticultural practices, including surface drip irrigation, weed control, pest management, and other cultural operations, were applied across all plots. Post-treatment, soil samples were collected at depths of 0–30, 30–60, and 60–90 cm to measure pH, EC, organic carbon, and available phosphorus. Foliar sprays were prepared with 1,000 ml solutions of urea and potassium sulfate (10 g/L), zinc sulfate (3 g/L), and boric acid (5 g/L) and applied twice at sunset using a handheld sprayer. Fruit yield, oil content, and selected oil quality parameters were then assessed.
Results and Discussion
Application of biologically enriched vermicompost significantly improved olive yield and oil quality. Trees receiving this treatment produced 50.33 kg of fruit per tree—an increase of 93.58% compared to the control. Similarly, the highest oil yield (11.14 kg per tree) was recorded in the biologically enriched vermicompost treatment. The lowest peroxide value (1.06 meq O₂/kg oil) was also observed in this treatment, representing an 88.27% reduction compared to the control. Organic fertilizers positively influenced the oil percentage of the fruit, with biologically enriched compost yielding the highest oil content (57.77%), which was 132.19% higher than the control. The extinction coefficients K270 and K232, indicators of oil oxidation, were reduced by 96.24% and 78.53%, respectively, in the biologically enriched vermicompost treatment. Furthermore, this treatment resulted in the lowest free fatty acid content—94.66% lower than the control. Leaf phosphorus content was also significantly enhanced, reaching 0.33% in the biological vermicompost treatment, a 230% increase over the control. These findings underscore the beneficial role of organic fertilizers, particularly biologically enriched vermicompost, in improving soil fertility, nutrient availability, and plant performance. The high phosphorus content in the compost and vermicompost, combined with microbial activity, played a pivotal role in enhancing both yield and oil quality. The application of PGPRs proved particularly effective, as they not only facilitated nutrient cycling but also contributed to improved physiological responses in olive trees.
Conclusions
Overall, the results suggest that olive trees fertilized with biologically enriched organic amendments derived from olive pomace benefit from improved oil quality and fruit yield. The presence of adequate phosphorus and beneficial bacteria played a pivotal role in enhancing plant nutrition and oil characteristics. Therefore, the use of PGPR in the enrichment of composted organic materials can be an effective and sustainable strategy to improve the productivity and quality of olive oil. Among the treatments, biologically enriched vermicompost emerged as the most effective and is recommended for further field application. Future research should explore other organic amendments and their long-term effects on olive orchards.
Soil science
S.S. Hosseini; F. Rejali; P. Keshavarz
Abstract
Introduction
Water scarcity is a major challenge in Iran, with annual rainfall averaging 235 to 260 mm, only a third of the global average. Wheat, a staple crop in Iran, faces severe yield reduction under drought conditions. Utilizing biofertilizers like plant growth-promoting rhizobacteria ...
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Introduction
Water scarcity is a major challenge in Iran, with annual rainfall averaging 235 to 260 mm, only a third of the global average. Wheat, a staple crop in Iran, faces severe yield reduction under drought conditions. Utilizing biofertilizers like plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal (AM) fungi could help enhance water use efficiency (WUE) and yield in such environments. However, the effectiveness of biofertilizers varies based on several factors, including the type of biofertilizer (bacterial or fungal), the strain or species used, and the formulation (solid or liquid). Despite the established benefits of both PGPR and AM fungi in enhancing drought tolerance and WUE, there is a lack of comparative studies that examine the specific performance of bacterial versus fungal biofertilizers and their formulations under varying levels of water stress. Thus, the objectives of this study are as follows: 1) to identify the most suitable type of biofertilizer (bacterial or fungal) for improving wheat yield and WUE under drought conditions in Mashhad's climatic conditions; 2) to determine the effect of ACC deaminase enzyme on the efficiency of PGPR in enhancing wheat yield and WUE; 3) to compare the performance of AM fungal biofertilizers in two formulations (powder and liquid) and between single-species and multi-species inoculants.
Material and Methods
The experiment was conducted as a split-plot design with three replicates, where irrigation levels constituted the main plots, and biofertilizer treatments formed the subplots. The irrigation treatments included full irrigation (100% of wheat’s water requirement), mild drought stress (85%), and severe drought stress (65%). The biofertilizer treatments were: no biofertilizer (F1), serving as a control; Pseudomonas fluorescens producing ACC-deaminase (F2); P. fluorescens without ACC-deaminase (F3); AM fungi (Rhizophagus irregularis) in liquid form (F4); and (5) AM fungi (R. irregularis, Funneliformis mosseae, and Claroideoglomus etunicatum) in powdered form (F5).
Results and Discussion
Both irrigation levels and biofertilizer types had significant impacts on root colonization, yield, and WUE. Reducing irrigation from 100% to 85% and 65% of crop water requirements significantly reduced root colonization across all treatments. Among the bacterial treatments, only P. fluorescens producing ACC-deaminase (F2) showed a significant positive effect under severe drought (65% irrigation). This treatment increased grain yield by 9%, biological yield by 7%, and WUE by 6.8% compared to the control (F1). The presence of ACC-deaminase likely contributed to mitigating the effects of drought-induced ethylene, promoting better root growth and nutrient uptake under water stress. In contrast, P. fluorescens without ACC-deaminase (F3) did not significantly improve yield or WUE, emphasizing the importance of ACC-deaminase in promoting drought tolerance. Fungal biofertilizers outperformed bacterial treatments in grain and biological yield, as well as WUE. Under severe drought, powdered AM fungi (F5) increased grain yield by 26% and biological yield by 21% compared to the control, and WUE based on grain yield improved by 26%. This superior performance of AM fungi, particularly in powdered form, can be attributed to their ability to enhance nutrient and water uptake under drought conditions. These findings corroborate earlier studies that demonstrated AM fungi's ability to improve crop yield and WUE under drought stress by enhancing water uptake, nutrient availability, and improving the plant's physiological responses, such as maintaining cell membrane stability and increasing antioxidant activity. The powdered formulation of AM fungi (F5) showed greater effectiveness than the liquid form (F4). The higher colonization rates and performance in yield improvement may be due to the inclusion of multiple fungal species in the powdered form. The performance differences between the liquid and powdered AM fungi formulations may also be influenced by the physical properties of the biofertilizer since powdered inoculants are most effective when applied to the seeds of grasses like wheat and barley, as the structure of these seeds allows for better adhesion of the powder.
Conclusion
In conclusion, among the bacterial biofertilizers, only P. fluorescens producing ACC-deaminase significantly enhanced plant performance under severe drought, underscoring the importance of ACC-deaminase in alleviating drought stress. However, fungal biofertilizers, especially in powdered form, were more effective overall in improving yield, biological productivity, and WUE under varying levels of water stress. This research confirms that the application of AM fungi can serve as an effective strategy for improving wheat yield and increasing WUE in the climatic conditions of Mashhad. Overall, the observed differences in the effectiveness of these biofertilizers suggest that the appropriate selection of both type and formulation of biofertilizers can significantly contribute to managing water stress and improving crop production.
Soil science
N. Khalili; R. Ghorbani Nasrabadi; M. Barani Motlagh; R. Khodadadi
Abstract
Introduction Actinobacteria are one of the most abundant microbial groups in soil and play a crucial role in preserving ecosystems. They are among the soil microbial groups capable of releasing phosphorus from low-soluble or insoluble phosphorus sources, which enhances plant growth. Their application ...
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Introduction Actinobacteria are one of the most abundant microbial groups in soil and play a crucial role in preserving ecosystems. They are among the soil microbial groups capable of releasing phosphorus from low-soluble or insoluble phosphorus sources, which enhances plant growth. Their application in agricultural systems is recognized as an environmentally friendly strategy to limit the negative effects of chemical inputs and improve the availability of nutrients, especially phosphorus, in the rhizosphere. Additionally, humic acid, as an organic growth stimulant, plays an important role in improving soil fertility and biological communities, and its combined use with actinobacteria increases the efficiency of fertilizer use, particularly phosphorus-based fertilizers. Therefore, the aim of this research was: (i) to screen the phosphorus solubilization potential of actinobacteria isolates at different incubation times, (ii) to investigate the effect of adding humic acid on the phosphorus solubilization capacity actinobacteria isolates under laboratory conditions, and (iii) to monitor the impact of selected actinobacteriun isolate and humic acid, at various phosphorus fertilizer levels, on soil phosphorus content, plant phosphorus uptake, and some biochemical properties of the soil. Materials and MethodsIn this study, five actinobacteria isolates, collected and purified from various agricultural, orchard, and rangeland ecosystems of Golestan Province, were screened based on their morphological characteristics. These strains were utilized for screening purposes. To prepare fresh cultures of the actinobacteria isolates, they were subcultured on solid yeast extract-malt extract agar medium. The effects of incubation time and the application of humic acid on the phosphate solubilization ability of the actinobacteria isolates were then investigated. This experiment was conducted in a factorial arrangement within a completely randomized design, with the following factors. To examine the effect of the selected superior actinobacterium isolate and its interaction with different phosphorus levels and humic acid application, a factorial pot experiment was conducted in a completely randomized design. The experimental factors included a mineral phosphorus source at three levels (control, 20 kg, and 40 kg of phosphorus per hectare from monoammonium phosphate), Streptomyces inoculation at two levels (control and inoculation with the selected isolate), and humic acid application at two levels (control and 2 mg per kg). The experiment was carried out on maize (Single Cross 704) with three replications. For seed preparation, a sufficient number of healthy maize seeds were selected and surface sterilized by immersing them in alcohol for 30 seconds. They were then exposed to 5% sodium hypochlorite for 2 to 3 minutes, followed by rinsing eight times with sterile distilled water. To prepare the microbial inoculum, the selected superior isolate was grown in yeast extract-malt extract medium at an appropriate (107 CFU/mL). The seeds were then placed in pots, and one milliliter of the Streptomyces suspension was applied to the seeds for inoculation. At the end of the experiment, the phosphorus content in the soil and plant, as well as the soil biochemical responses were measured. ResultsBased on the results obtained from this study, the application of humic acid led to an increase in microbial biomass and enhanced phosphorus release by actinobacteria isolates under laboratory conditions. As the incubation period extended from 7 to 14 days, the solubility of phosphate showed an increasing trend. The results showed that the highest phosphorus content in the soil was associated with the combined application of a high phosphorus level (40 mg per kg) along with humic acid and Streptomyces inoculation. Analysis of microbial biomass phosphorus revealed that the highest level was related to the treatment combining the highest level of phosphorus fertilizer and humic acid. According to the findings related to phosphatase enzymes, the combined application of the Streptomyces treatment, humic acid, and phosphorus resulted in an increase in the levels of these enzymes. Additionally, the results of microbial respiration in the soil indicated that the combined treatment of Streptomyces and the highest level of phosphorus fertilizer enhanced microbial respiration in the soil. The phosphorus content in the plants under the combined treatments of Streptomyces, humic acid, and phosphorus showed that the integration of Streptomyces inoculation and humic acid was effective in improving soil phosphorus availability and led to an increase in the phosphorus content of the plants. The results of this study showed that inoculation with the selected Streptomyces isolate, along with the combined application of humic acid, enhanced the efficiency of phosphorus fertilizer utilization, making it more readily available to the plant. Conclusion In general, the results of current study revealed that the simultaneous application of humic acid and Streptomyces inoculation led to an increase in the availability of phosphorus in the soil and the phosphorus content in the plants, as well as an improvement in the biochemical responses of the soil. However, field experiments are necessary to confirm its effectiveness.
Soil science
E. Fathi; M. Ekhtesasi; A. Talebi; J. Mosaffaie
Abstract
IntroductionWatersheds, as diverse ecosystems, play a fundamental role in water provision, soil conservation, biodiversity, and ecological sustainability. In addition to delivering environmental services, these areas serve as vital resources for supporting the livelihoods and well-being of local communities. ...
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IntroductionWatersheds, as diverse ecosystems, play a fundamental role in water provision, soil conservation, biodiversity, and ecological sustainability. In addition to delivering environmental services, these areas serve as vital resources for supporting the livelihoods and well-being of local communities. However, population growth, climate change, land-use changes, and overexploitation have imposed significant pressures on these ecosystems, jeopardizing their health and natural functionality. The degradation of these areas can lead to serious consequences for water resources, biodiversity, and environmental sustainability. Therefore, identifying and implementing effective strategies to preserve and enhance watershed health is essential. In this regard, the present study utilizes the strategic SWOT model to identify the strengths, weaknesses, opportunities, and threats within the Ilam Dam watershed and aims to propose practical solutions for improving and strengthening the health of these valuable ecosystems. Materials and MethodsTo achieve optimal strategies for resource management and improving the health of the study area, the SWOT analysis method was employed. This method provides a comprehensive framework for developing operational strategies by identifying existing strengths, weaknesses, opportunities, and threats. Data for this research were collected through field studies, specialized interviews with local experts, and a review of scientific resources and available information. To enhance accuracy and reliability in evaluating and weighting internal and external factors, the Analytic Hierarchy Process (AHP) and Expert Choice software were utilized. Subsequently, the collected data were analyzed using the Internal Factor Evaluation (IFE) and External Factor Evaluation (EFE) matrices, leading to the formulation of appropriate strategies. These strategies were categorized into four main types: aggressive, conservative, competitive, and defensive. Finally, to ensure the selection of the best options, the Quantitative Strategic Planning Matrix (QSPM) was applied. At this stage, each strategy was scored and prioritized based on its attractiveness and feasibility, ensuring the identification of the most effective and actionable strategies. Results and DiscussionAccording to the results of this study, seven factors were identified as strengths and seven as weaknesses (internal factors), along with seven opportunities and seven threats (external factors). The total score for strengths was 3.33, and for weaknesses, it was 3.57. Additionally, the score for opportunities was calculated at 3.54, while threats scored 3.28. Based on these scores and the internal and external factors evaluation matrix analysis, the WO strategy position was recommended, with specific solutions determined for each strategy. In the SO strategy, the QSPM matrix analysis indicated that optimal management of surface and groundwater resources, along with the establishment of suitable infrastructure for water capture and storage (strategy SO2), was recognized as the top priority. Within the ST strategy, the strategy of leveraging high organizational and local capacity to address the negative impacts of climate change and sustainably engage stakeholders and local communities in decision-making and watershed resource protection (strategy ST4) was prioritized. For the WO strategy, enhancing water and soil conservation programs and developing research and management initiatives through encouragement, support, and both material and spiritual contributions for specialized studies (strategy WO2) was identified as the main priority. Likewise, under the WT strategy, expanding and diversifying educational programs, developing educational content on water crises and climate change, and addressing the consequences of natural resource degradation in the basin, along with planning and approving national and international projects on climate change and dust storm mitigation (strategy WT1), emerged as the top priority. These strategies can provide an effective framework for improving resource management in watersheds and addressing environmental challenges. Conclusion The findings of this study clearly demonstrate that strengthening protective, managerial, and educational programs plays a crucial role in improving the health of this watershed. These strategies, by optimizing available opportunities and minimizing weaknesses, can significantly contribute to sustainable development and effective natural resource conservation. In particular, the implementation of these programs requires collaboration and synergy among the local community, governmental and non-governmental organizations, and related agencies. It is recommended that conservation and management planning be accompanied by education and awareness initiatives for the local community, so residents understand the importance of preserving natural resources and are encouraged to participate in conservation efforts. This active community involvement not only enhances the effectiveness of these strategies but also contributes to achieving desirable outcomes and ecosystem sustainability, setting the stage for more effective management and long-term conservation of water and soil resources.
Soil science
Z. Movahedi Rad; M. Hamidpour; A. Tajabadipour
Abstract
Introduction
Recently, layered double hydroxides (LDHs) with a unique structure and unbeatable characteristics have been widely studied and investigated in various fields. One of these fields is the investigating the potential of these compounds to supply essential nutrients for plants. Several studies ...
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Introduction
Recently, layered double hydroxides (LDHs) with a unique structure and unbeatable characteristics have been widely studied and investigated in various fields. One of these fields is the investigating the potential of these compounds to supply essential nutrients for plants. Several studies have reported the application of LDHs as fertilizers for macronutrients and micronutrients. These compounds have a very high potential as fertilizers and can increase agricultural productivity. Micronutrients such as Zn, Cu and Mn can be structurally incorporated in the metal hydroxide layer. According to recent research, LDHs have shown a suitable potential to release micronutrients. However, more studies are needed to enhance our understanding of the mechanism and reaction of layered double hydroxides in different conditions. Although various studies have explored the potential of LDHs as slow-release fertilizers, our research focuses on the role of citric acid and tartaric acid and as well as the ratio of divalent to trivalent cations on the kinetics of Zn, Mn and Mg release from Mg-Zn-Mn-Al-LDH intercalated with nitrate.
Materials and Methods
All chemicals used in this study including citric acid (C6H8O7.H2O), tartaric acid (C4H6O6) KCl, Zn (NO3)2.6H2O, Mn(NO3)2.4H2O Mg(NO3)2.6H2O and Al(NO3).9H2O were of analytical grades, purchased from Chem-Lab or Merck Chemical Corporations. Solutions were prepared using decarbonated ultrapure water (electrical resistivity = 18 MΩcm). The LDHs were synthesized by co-precipitation method at constant pH = 9.2-9.6. Two types of LDHs were synthesized by varying the M+2(Zn+Mn+Mg)/M+3(Al) ratios of 3:1 and 4:1 in the precursor solution while stirring vigorously in a nitrogen atmosphere. The pH was kept at 9.2-9.6 by adding volumes of 3 M NaOH. The LDH crystals were allowed to ripen in the mixture for 2 hours, after which the precipitates were centrifuged at 3000 rpm for 20 min and washed several times with distilled water and placed in an oven at 70°C for 8 hours to dry.
The chemical composition of the synthesized layered double hydroxides (LDHs) was analyzed using furnace atomic absorption spectrophotometry (SavantAA, GBC) following acid digestion. The physical, chemical, and morphological characteristics of the LDHs were assessed through several techniques, including X-ray diffraction (Panalytical X Pert Pro X-ray diffractometer), field emission scanning electron microscopy (FE-SEM, Sigma VP), Fourier-transform infrared spectroscopy (FT-IR, Nicolet iS10 spectrometer), and Brunauer-Emmett-Teller (BET, BELSORP Mini II) analysis.
A batch study was conducted to evaluate the effects of varying M²⁺/M³⁺ ratios in LDHs and the influence of citric acid and tartaric acid on the release of Zn, Mn, and Mg from LDH (3:1) and LDH (4:1). In brief, 0.01 g of synthesized LDH was placed in a centrifuge tube and mixed with 10 ml of background electrolyte (0.01 M KCl) and 1.25 mM of citric acid or tartaric acid, maintaining an initial pH of 6–7 at a constant temperature of 25 ± 0.5 °C. Blank samples (without ligands) were also included for comparison. The suspensions were shaken for time periods ranging from 5 to 720 minutes at an agitation speed of 180 rpm. After shaking, the supernatant was separated by centrifugation at 4000 rpm for 20 minutes. The concentrations of Zn, Mn, and Mg in the supernatant solutions were determined using graphite furnace atomic absorption spectrophotometry.
To describe the time-dependent release of Zn, Mn, and Mg, several kinetic models were tested. Among the five models evaluated, the pseudo-second-order and power function models provided the best fit for the kinetic data. Additionally, the chemical species present in the initial solution and the saturation index (SI) of various minerals were predicted using the Visual MINTEQ 3.1 computer code.
Results and Discussion
The results indicated that the calculated molar ratio of divalent cations to trivalent cations closely matched the molar ratios used in the synthesis of the layered double hydroxide (LDH) samples. The X-ray diffraction (XRD) patterns for both LDH (3:1) and LDH (4:1) samples exhibited strong and sharp peaks corresponding to the 003 and 006 reflections, confirming the layered structure of the synthesized materials. Fourier-transform infrared (FT-IR) spectroscopy revealed two significant absorption bands around 3480 cm⁻¹ and 1620 cm⁻¹ in all synthesized LDH materials, which are indicative of stretching vibrations associated with the O-H groups in the hydroxide layers and the interlayer water molecules. Additionally, a sharp band at approximately 1382 cm⁻¹ in LDH (3:1) and a band at around 1354 cm⁻¹ in LDH (4:1) were attributed to the antisymmetric stretching mode of the nitrate anion present in the LDH structure. The specific surface areas of LDH (3:1) and LDH (4:1) were measured at 5.50 m²/g and 16.54 m²/g, respectively. Correspondingly, the average pore diameters were found to be 1.92 nm for LDH (3:1) and 2.55 nm for LDH (4:1), indicating differences in porosity between the two samples. The time-dependent cumulative release of Zn, Mn, and Mg from LDH (3:1) and LDH (4:1) in the presence and absence of citric acid and tartaric acid was investigated. The release of these micronutrients was accelerated in the presence of both organic acids. The release process appeared to occur in two stages: during the initial stage (0 to 50 minutes), the release rate of Zn, Mn, and Mg was rapid, followed by a period from 50 to 720 minutes where the release rate either fixed or slightly increased.
In this research, among the non-linear models which were used to determine the release kinetics of Zn, Mn, and Mg, the one with the highest R2 values was chosen. The R² values ranged from 0.81 to 0.99 for the pseudo-first-order model, 0.89 to 0.93 for the pseudo-second-order model, 0.97 to 0.99 for the Elovich model, 0.89 to 0.99 for the power function model, and 0.55 to 0.86 for the parabolic diffusion model. Ultimately, the pseudo-second-order and power function models were chosen to analyze the kinetic data. The amount of Zn, Mn and Mg released at equilibrium (qe) were higher in the presence of citric acid (42%) compared to tartaric acid. Additionally, the release of these elements was greater from LDH (4:1) than from LDH (3:1). This suggests that increasing the ratio of divalent cations to trivalent cations reduces the stability of LDH, enhancing the release of micronutrients.
Conclusion
The results of this study demonstrated that the release of Zn, Mn, and Mg from layered double hydroxides (LDHs) was influenced by time, the type of low molecular weight organic acid, and the ratio of divalent to trivalent cations in the LDH structure. Kinetic modeling revealed that the release rates of Zn, Mn, and Mg from LDH with a 4:1 ratio were higher than those from LDH with a 3:1 ratio. Additionally, the dissolution rates of LDHs were faster in the presence of citric acid compared to tartaric acid. To further assess the potential of LDHs as slow-release micronutrient fertilizers in calcareous soils, additional greenhouse and soil experiments are recommended.
Soil science
A. Ansori Savari; , M. Nabipour; M. Farzaneh
Abstract
IntroductionThe high water demand of sugarcane in arid and semi-arid regions, combined with declining rainfall, has led to increased use of drainage water as a strategy for sustainable production management. It has been estimated that 20% of all cultivated land and 33% of irrigated agricultural land ...
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IntroductionThe high water demand of sugarcane in arid and semi-arid regions, combined with declining rainfall, has led to increased use of drainage water as a strategy for sustainable production management. It has been estimated that 20% of all cultivated land and 33% of irrigated agricultural land are affected by high salinity. Salinity stress poses two main threats to plants: ionic toxicity and osmotic stress. Ionic toxicity occurs when there is a significant accumulation of Na⁺ in plant leaves under saline conditions. This disrupts the balance of water and ions, damages organelle structures, inhibits growth, and can ultimately lead to plant death. Some studies have shown that ion toxicity caused by Na+ can inflict more irreversible damage on plants than osmotic stress. Silicon application (Si) showed improved photosynthetic efficiency, growth, and yield compared to plants under salt stress. Previous studies have also shown that silicon treatments can increase salinity tolerance in various plants, including wheat, corn, rice, and canola. However, the extent of silicon-mediated benefits under salinity can vary greatly between species and is largely dependent on the plant's capacity for element uptake dictated by its genetic makeup. There is limited information regarding the use of drainage water in sugarcane irrigation management in arid and semi-arid regions, as well as the potential for improving salinity stress through silicon application. Therefore, this study was conducted to evaluate the effects of Si on two sugarcane varieties irrigated with salt water. Materials and MethodsThe pot experiment was conducted in a greenhouse under natural light at the agricultural site of Sugarcane Dehkhoda Company in Khuzestan Province, Iran, in 2021-2022. The temperature and humidity percentages are indicated in Figure 1. This study was carried out as split-split plot design based on randomized Block design (RBD). The main plot factors included three levels of salinity: control of 1.4±0.2 dS.m-1 (S0) from the river water source, salinity stress of 4.1±0.2 dS.m-1 (S1), and salinity stress of 8.2±0.2 dS.m-1 (S2) from the drain water source, with a sub-factor of variety treatment (CP73-21 and CP69-1062). The silicon application timing was also considered as a sub-factor, with four levels: Si0, non-silicon application (Control); Si1, one month before salinity stress; Si2, during salinity stress; and Si3, after 30 days of salt stress, silicon was applied. The sugarcane sprouts are grown in polyethylene pots 100 cm in height and 45 cm in width. Each pot contained 100 kg of soil. A total of 216 experimental units were used during the experiment. The experimental pots were filled with a mixture of field soil and sugarcane filter cake in a 3:1 ratio. The results of the chemical analysis of field soil and filter cake are presented in Table 2. The salt stress was applied 113 days after growing cuttings and continued until harvest. Results and DiscussionThe results of the first year showed that salt stress significantly reduced the height of the sugarcane stalk. Also, at the salinity stress levels of 4.1 and 8.2 dS/m, the SPAD index decreased by 22.3% and 27%, respectively. Additionally, leaf sheath moisture dropped by 6.4% and 11.8%, electrolyte leakage increased by 11% and 22.7%, and the photosynthesis rate decreased by 28% and 42% compared to the control treatment. The optimal time to apply silicone fertilizer was one month prior to the onset of stress, which resulted in a significant improvement in all studied traits at salinity stress levels of 1.4 dS/m (control) and 4.1 dS/m. Furthermore, the qualitative analysis of sugarcane syrup in the second year revealed a decrease in sucrose percentage (14.1% and 33.5%, respectively) and white sugar content (12.6% and 40.9%, respectively) at salinity stress levels of 4.1 and 8.2 dS/m. The photosynthesis rate of sugarcane leaves decreased by 28.3 to 41.8 percent under salt stress levels of 4.1 and 8.2 dS, respectively. The CP69-1062 variety exhibited a better response compared to the CP73-21 variety, showing relative superiority in all growth and physiological traits studied. Conclusion The results also indicated that the optimal time to apply silicon fertilizer to sugarcane plants was one month before the onset of stress, resulting in a significant improvement in all studied traits. The application of silicon fertilizer led to a 1 percent increase in sucrose, 3.7 percent increase in syrup purity, and 3 percent increase in white sugar yield compared to no application. Acknowledgments We would like to express our special thanks to the Faculty of Agriculture, Shahid Chamran University of Ahvaz for the financial support (Grant number SCU.AA98.336).
Soil science
Sh. Moradi; M.R. Sarikhani; A. Beheshti Ale Agha; A. Reyhanitabarَ; S.S. Alavi-kia; A. Bandehagh; R. Sharifi
Abstract
IntroductionOil contamination affects the biological, physical, and chemical properties of soil. The abundance and diversity of soil microbial communities can significantly be influenced by petroleum hydrocarbons. Soil biological indicators including microbial population and enzyme activity, are highly ...
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IntroductionOil contamination affects the biological, physical, and chemical properties of soil. The abundance and diversity of soil microbial communities can significantly be influenced by petroleum hydrocarbons. Soil biological indicators including microbial population and enzyme activity, are highly sensitive to environmental stresses and respond to them quickly. Measuring the microbial population is one of the most common biological indicators which is used to study the quality and health of the soil. Also, measuring the activity of enzymes such as urease is one of the most sensitive indicators of oil-contaminated soils. There are some studies on the effects of oil contamination on microbial population and soil enzyme activity. Most of the studies have tested non-natural and short-term oil pollution and reported the adverse effects of oil hydrocarbons on microbial activities in soil. While the soil sample used in this research had natural and long-term contamination and the microorganisms are compatible with polluted conditions. The aim of this study was to investigate changes in the microbial population and urease activity in the presence of different levels of oil contamination, and how petroleum hydrocarbons can affect them. Petroleum hydrocarbons are toxic and persistent in soil, so it is necessary to study the pattern of changes in soil biological characteristics in effective soil management. Material and MethodsIn this study, 120 samples of oil-contaminated soils were collected from the oil-rich area of Naft-Shahr (located in the west of Kermanshah province) which had natural and long-term oil pollution. A nested design was used to analysis data in this research. The test factors included locations (4 locations) and 3 different levels of oil pollution: low (L), moderate (M), and high (H). Also, 10 replications were considered in the three levels of oil contamination. The collected soils were analyzed for physico-chemical (pH, EC, Ɵm, CCE, OC, soil texture) and biological properties (including urease activity, BR and SIR) using standard methods, and the concentration of oil pollutants was determined by the Soxhlet extractor. To determine the abundance of the culturable microbial population, bacterial counting was performed using nutrient agar (NA) and carbon-free minimal medium (CFMM) supplemented with crude oil as the media. Urease activity was measured by the indophenol blue method and finally, the results of measuring chemical, physical and biological properties were analyzed using principal component analysis (PCA). Results and Discussion The average percentage of oil measured by Soxhlet method was 4.03%, 9.95% and 22.50% respectively for L, M and H levels. The results showed that the microbial population increased with the increase of contamination intensity. The highest microbial population counted in NA culture medium was 9.54 ×105 CFU/g in H soils and the lowest population was 3.25 × 105 CFU/g in L soils. In the CFMM culture medium, the highest population in H soils was 11.3 × 105 CFU/g and the lowest population in L soils was 11.8 × 104 CFU/g. For both NA and CFMM mediums, location 1 had the highest population and location 4 had the lowest microbial population. Oil contamination of soil samples led to a decrease in urease activity in such a way that the highest enzyme activity in soils was obtained with low contamination (594.90 µgNH4/g.h) and the lowest activity in heavily contaminated soils (176.11 µgNH4/g.h). Also, the lowest urease activity was observed in location 1 and the highest in location 4. Principal components analysis (PCA) was also performed and 71% of the variance of the samples could be explained by the first two components (biochemical component and physical component). The results of this research indicated an increase in the microbial population with an increasing of the intensity of oil pollution. It seems that the results obtained from the studies conducted on man-made pollution and natural pollution have differences in terms of the type of biological responses. Aged, long-term and natural oil pollution has caused the selection of oil-resistant microbial community, and therefore we see their positive response to the presence of oil compounds. Conversely, urease enzyme activity was found to be higher in soils with low pollution. This suggests that microbial activity, while influential, is not the sole determinant of urease activity, and various factors contribute to Soil Enzyme Activity (SEA). The type of petroleum pollutant, the direct effect of petroleum compounds on urease-producing microorganisms, as well as the non-microbial origin of urease in soil can be possible reasons for reducing urease activity in contaminated soils. ConclusionIn areas where petroleum pollutants are naturally and long-term present in the soil, some oil-decomposing microbial groups use petroleum hydrocarbons as a source of carbon for their nutrition, so the abundance of oil-decomposing communities increases. The results showed an increase in the microbial population with an increase in the intensity of oil pollution. On the other hand, the activity of urease enzyme measured in soils with low pollution was higher because non-microbial factors may affect the activity of this enzyme and the increase in the microbial population is not related to the increase in the population of urease-producing microbes.
Soil science
Yahya Kooch; Mahmood Tavakoli Feizabadi; Katayoun Haghverdi
Abstract
IntroductionSoil, as habitat substrate, helps to regulate important ecosystem processes, including nutrient absorption, organic matter decomposition. Water availability and the well-being of humanity are directly linked to soil functions. On the other hand, vegetation with different species and ages ...
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IntroductionSoil, as habitat substrate, helps to regulate important ecosystem processes, including nutrient absorption, organic matter decomposition. Water availability and the well-being of humanity are directly linked to soil functions. On the other hand, vegetation with different species and ages have significant effects on the status of the surface soil layer through the creation of diverse environmental conditions and the production of different organic substances. However, few studies have been conducted in relation to the effect of the age of afforestation and the type of vegetation on the soil status. Considering that a practical, complete and effective assessment of soil condition should be the result of simultaneous measurement of physical, chemical and biological indicators, hereupon, the present study aimed to investigate the effect of 20-year old poplar stand, 20-year old maple stand, 10-year old poplar stand, 10-year old maple stand and rangeland cover, in plot 3 of Delak-Khil series of wood and paper forests in Mazandaran province, on the organic layer properties and physical, chemical and biological (including microbial activities, enzyme activity, earthworm population and biomass, the number of soil nematodes and root biomass) properties of the surface soil layer. Materials and MethodsFor this purpose, some parts of the study area were selected which are continuous with each other and have minimum height difference from the sea level, minimum change in percentage and direction of slope. Then, in order to take samples from the organic and surface layer of the soil, three one-hectare plots with distances of at least 600 meters were selected in each study habitats. From each of the one-hectare plots, 5 leaf litter samples and 5 soil samples (30 cm × 30 cm by 10 cm depth) were taken to the laboratory for analysis . In total, 15 litter samples and 15 soil samples were collected from each of the habitats under study. One part of the soil samples was passed through a 2 mm sieve after air-drying to perform physical and chemical tests, and the second part of the samples was kept at 4 °C for biological tests. One-way analysis of variance tests was used to compare the characteristics of organic layer and soil between the studied habitats. In the following, Duncan's test (P>0.05) was used to compare the average parameters that had significant differences among different habitats.Results and DiscussionThe results of this research showed that afforested stands with different ages and pasture cover had a significant effect on the characteristics of the organic and surface soil layers. The results indicated the improvement of most of the characteristics of the organic and surface soil layer in the afforested stands, especially the 20-year old afforestation compared to the rangeland cover. The organic matter produced in 20-year old afforestation, especially with poplar species, had a higher quality (high nitrogen and carbon content and low carbon-to-nitrogen ratio) compared to organic matter produced in 10-year old afforestation and pasture cover. Most of the physicochemical characteristics of the soil under 20-year old afforestation were in a better condition than the other studied habitats. Also, according to the results of this research, the highest values of biological characteristics such as microbial activity, enzyme activity, and the population of earthworms and nematodes were observed in the subsoil of 20-year old afforestation especially with poplar species. Based on the results obtained from the principal component analysis, the higher values of nitrogen, phosphorus, calcium, magnesium and potassium content of the organic layer led to the improvement of soil fertility characteristics, microbial activities, enzyme activity, earthworm population, the number of soil nematodes and root biomass, respectively, under poplar and maple plantation for 20 years, meanwhile, 10-year old plantation, especially with maple species, and rangeland with the production of organic materials with high carbon content and carbon to nitrogen ratio, resulted in the reduction of organic matter decomposition (greater thickness of organic layer), and consequently the reduction of the mentioned properties of the surface soil layer. ConclusionAccording to the findings of this research, it can be concluded that plantation with poplar species, especially after 20 years, had a higher ability to improve the soil condition compared to maple, which can be considered by managers in future afforestation. Also, with the passage of time, the presence of tree covers (poplar and maple) had a higher priority than rangeland cover in improving the fertility status and suitable edaphological conditions of the soil.
Soil science
Mehdi Zangiabadi
Abstract
IntroductionSoil pore size distribution curve and using the optimal ranges of the location and shape parameters of this curve can be used to evaluate the soil physical quality. This research was carried out in an area of about 220 hectares of Torogh Agricultural and Natural Resources Research and Education ...
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IntroductionSoil pore size distribution curve and using the optimal ranges of the location and shape parameters of this curve can be used to evaluate the soil physical quality. This research was carried out in an area of about 220 hectares of Torogh Agricultural and Natural Resources Research and Education Station, to determine the optimal ranges for soil pore size distribution curve parameters using the soil physical quality index. Different soil textures and the diversity in soil properties are the distinct features of this research station. Materials and MethodsTorogh Agricultural and Natural Resources Research and Education Station of Khorasan-Razavi province, with a semiarid climate, is located in south-east of Mashhad city. For the field measurements and laboratory analysis to determine the soil physical properties and indices, 30 points with different soil textures and structures were selected. Intact soil cores (5 cm diameter by 5.3 cm length) and disturbed soil samples were collected from 0-30 cm depth of each point. After the laboratory analysis and field measurements, 35 soil physical properties were measured and calculated. Soil particle size distribution and five size classes of sand particles, soil bulk, and particle density, dry aggregates mean weight diameter (MWD) and stability index (SI), soil moisture release curve (SMRC) parameters, S-index, soil porosity (POR) and air capacity (AC), soil pore size distribution (SPSD) curves, relative field capacity (RFC), plant available water measured in matric pressure heads of 100 and 330 hPa for the field capacity (PAW100 and PAW330), least limiting water range measured in matric pressure heads of 100 and 330 hPa for the field capacity (LLWR100 and LLWR330), integral water capacity (IWC) and integral energy (EI) of different soil water ranges, were the soil physical properties and indices which were determined in this study. Three parameters of modal, median, and mean pore sizes of the SPSD curves were considered as the location (central tendency), and three parameters of standard deviation, skewness, and kurtosis of the SPSD curves were considered as the shape parameters. Selection of the most important soil physical characteristics using principal component analysis (PCA) method by JMP software (ver. 9.02), weighting and scoring of the selected characteristics using PCA and scoring functions, respectively, and the summation of multiplied characteristics weights by their scores for each soil sample, were the four steps of calculation of the 0-1 value of soil physical quality index (SPQI). Soil samples were classified into four soil physical quality classes by SPQI values. The soils of the first class with the highest SPQIs (> 0.78) were considered to determine the optimal ranges of SPSD curves location and shape parameters. Results and DiscussionThe texture of soil samples were loam (40 %), silt loam (23 %), silty clay loam (17 %), clay loam (13 %), and sandy loam (7 %). Soil organic carbon was between 0.26-1.05 (%), and the average soil bulk density was 1.45 (gr.cm-3). The MWD values of studied soil samples were between 0.94-2.88 (mm), an average of 1.93 (mm). The average modal, median, and mean pore sizes as the location parameters of the SPSD curves were 60.3 (μm), 12.4 (μm), and 6.5 (μm), respectively. The average of standard deviation, skewness, and kurtosis as the shape parameters of the SPSD curves were 71.56 (μm), -0.36 and 1.15, respectively. The average modal pore sizes showed that the pores with a size of 60 (μm) had the highest frequency in soil samples. The range of calculated standard deviation of SPSD curves, along with the difference between the minimum and maximum mean pore sizes (24.6 μm), implied the diversity of pore sizes in the studied soils. The results of PCA showed that the four soil physical properties of PAW330 (0.1-0.2 cm3.cm-3), PORt (0.40-0.51 cm3.cm-3), LLWR100 (0.12-0.22 cm3.cm-3) and SI (0.76-2.61 %) accounted for about 88% of the variance between soil samples and were selected to calculate the SPQIs. The PAW330, PORt, LLWR100, and SI were entered into the calculation of SPQIs with weights of 0.46, 0.31, 0.15, and 0.08, respectively. All the selected physical properties were scored using the scoring function of more is better. The maximum and minimum values of SPQIs for the studied soils were 0.84 and 0.14, respectively. Five soil samples with SPQIs greater than 0.78 were classified as class 1 with the highest physical quality. The ranges between the minimum and maximum values of the SPSD curves, location, and shape parameters of these five soils were proposed as the optimal ranges. In this regard, the ranges of 29-92 (μm), 5-16 (μm), and 2-7 (μm) were suggested for optimal ranges of modal, median, and mean pore sizes, respectively. The optimal ranges of standard deviation, skewness, and kurtosis of the SPSD curves were proposed as 22-81 (μm), (-0.38)-(-0.33), and 1.14-1.15, respectively. ConclusionThe optimal ranges of SPSD curves location and shape parameters suggested in the literature may probably not apply to a wide range of agricultural soils. They must be evaluated in a more extensive range of land uses, soil management, and soil textures. In this research, the soils with the relatively higher physical quality had larger mean pore size and less SPSD curves standard deviation (less diversity of pore size) than the optimal ranges suggested in the literature. The optimal ranges of SPSD curves location and shape parameters proposed in this research are appropriate for medium to coarse-textured soils of regions with the semiarid climate in Iran.
Soil science
Mahvan Hasanzadeh Bashtian; Alireza Karimi; Adel Sepehr; Amir Lakziyan; Omid Bayat
Abstract
Introduction
Soils and landforms have a strong relationship and archive evidence of climatic and environmental changes. Alluvial fans are one of the most important landforms in arid and semi-arid regions of Iran. Climate changes in the Quaternary, especially in the late Pleistocene, had a significant ...
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Introduction
Soils and landforms have a strong relationship and archive evidence of climatic and environmental changes. Alluvial fans are one of the most important landforms in arid and semi-arid regions of Iran. Climate changes in the Quaternary, especially in the late Pleistocene, had a significant effect on the evolutions of alluvial fans in arid and semi-arid regions. Alternate of sedimentation and soil formation in alluvial are the consequences of periodic climate change. Organisms are one of the main factors of soil formation. Biological crusts are part of organisms that are abundant in dry lands and especially in alluvial fans; however, their role in soil formation has been less studied. Biological soil crusts by providing the suitable biological activity, effect on trapping of aeoilian materials and hydrological processes affect the soil formation processes. The chemical properties of the soil affect the catabolic capacity of the soil and it is very different among the different layers of the soil. However, few studies have addressed the effect of processes on soil microbial respiration during change and evolution and pedogenic state. The objectives of this research were to 1) investigate the evolution of soils along the gradient from upstream to downstream of the alluvial fan and 2) investigate the changes in microbial respiration in different layers of soil and the factors affecting it.
Materials and Methods
The studied area is an alluvial fan in Razavi Khorasan province, in the southern slopes of the Binaloud mountain range. The climate of the region is semi-arid and the soil moisture and temperature regimes are Aridic border on Xeric and mesic, respectively. Three soil profile in the upper, middle, and base part of the alluvial fan were described. Bulk and undisturbed soil samples were collected from various soil horizons for subsequent physical, chemical, and micromorphological analyses. In addition, the microbial soil respiration was measured in all horizons. The soils were classified according to Soil Taxonomy and World Reference Base methods.
Results and Discussion
Sequences of sedimentation and soil formation were observed in the soil profiles. Vesicular (V), argillic (Bt), argillic-calcic (Btk), calcic (BCk) and cambic (Bw) horizons were the diagnostic soil horizons of the studied soils. Soil profiles of the middle and base were Xeric Calciargids in the subgroup category of Soil Taxonomy; while soil profile of the apex soil was Xeric Haplocambids. In the profiles, a thin vesicular horizon (V) was formed under the desert pavement. Below the vesicular horizon, evidence of clay illuviation, pedogenic carbonate nodules, and calcium oxalates in roots were observed in thin sections. This evidence shows the role of biological crusts in the formation of these features. In the lower horizons of the profiles, pedogenic carbonate nodules, carbonates pendants and clay coatings were observed. It seems that the upper soil (vesicular and underlying Bt horizons) were developed in the more humid periods of the Holocene, and biological crusts also played a key role in the processes of calcification and clay illuviation. The argillic horizons in the lower layers were formed during the stable periods of the late Pleistocene. The irregular microbial respiration mainly indicated difference in microbial activities labile organic matter content. The argillic horizons had the lowest microbial respiration, due to decomposition of organic materials during soil formation. In contrast, soil respiration was the highest in surface and calcic horizons. It seems that preservation of organic materials by carbonate complication. However, it is suggested to investigate the carbon fractions in relation to microbial biomass in the studied horizons.
Conclusion
In this area, biological crusts and vegetation affected the formation of soil in the aeolian sediments of the Vk and AVk horizons and played a significant role in creating the Bt horizon in profiles 2 and 3. The study of landform profiles showed the formation of calcic and argillic horizons in the past climate, while the Bt horizon of the upper layers was formed in the current Holocene period. This form of the argillic horizon is slightly different from the soils of the Iranian region because these horizons have not been reported so far. It has been proven that there were humid periods in the Holocene, and it needs more studies at present. The study of soil microbial respiration in landform horizons showed that argillic horizons decreased the amount of microbial respiration, while it increased in classical horizons.
Soil science
Maryam Ghorbani; shahram kiani; Ali Moharrery; Sina Fallah
Abstract
IntroductionThe gradual decrease in the fertile soils surface due to environmental pollution and urbanization phenomena has reduced the possibility of sufficient fodder production. In addition, the strict dependency of the agricultural sector on water resources in an age of drastic climate change ...
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IntroductionThe gradual decrease in the fertile soils surface due to environmental pollution and urbanization phenomena has reduced the possibility of sufficient fodder production. In addition, the strict dependency of the agricultural sector on water resources in an age of drastic climate change necessitates providing novel solutions for agricultural production. One of the methods that has gained attention for providing fodder is its production through soilless culture techniques. Maize can be a suitable option for fodder production in soilless culture due to high starch and sugar content, low seed cost, high biomass production, and rapid growth. Proper nutritional management of maize in soilless culture is highly important for increasing the quantity and quality of forage greenery. Little information is available regarding the impact of nitrogen form on the growth, yield and chemical composition of forage plants including maize in soilless culture. This experiment was conducted to investigate the effect of nitrogen form on the chemical composition, leaf photosynthetic pigments concentration and yield of two fodder maize (Zea mays L.) cultivars in soilless culture. Materials and MethodsA factorial experiment based on randomized complete block design was conducted with the two factors of ammonium to nitrate ratio in the nutrient solution (0:100, 12.5:87.5, 25:75, 37.5:62.5 and 50:50) and maize cultivars (i.e., single cross hybrid 704 and single cross 410) and four replications in hydroponic culture at the greenhouse of Shahrekord University. After seed germination and emergence of the first two leaves, the maize seedlings were transferred to 10-liter plastic pots containing perlite (0.5-5 mm) and were manually fertigated with different ammonium to nitrate ratios on a daily basis. Before harvesting, chlorophyll a, b and (a+b), and carotenoids were quantified in leaves of plants. At the end of the tasseling stage, the plants were harvested. After harvesting, the root, stem, and leaf parts were separated, and the fresh weights of the samples were measured. Plant samples were dried in an oven at 60 °C. Then, dry weights of samples were measured and samples (root and leaf + stem) were ground for nutrient analysis including of N, P and K. Analysis of variance was performed using SAS software version 9.4. Means comparison was conducted using Duncan's multi-range test at p <0.05. Results and DiscussionThe results showed that in single-cross hybrid 704 and single-cross 410 cultivars, respectively, increasing the applied ammonium to 37.5% and 50% in the nutrient solution caused a significant increase in the shoot nitrogen concentration. Application of ammonium in the nutrient solution led to an increase in shoot and root phosphorus concentration in both maize cultivars compared to the nutrient solution without ammonium. The highest concentration of phosphorus in shoot (18.02 g.kg-1) was observed in the single-cross hybrid 704 cultivar when maize plants fed with a nutrient solution containing 50 percent ammonium, which was 3.2 times higher than the shoot phosphorus concentration in plants fed with nutrient solution without ammonium. Furthermore, at the 50:50 ammonium to nitrate ratio in the nutrient solution, the lowest root potassium concentration was recorded in both maize cultivars. In single-cross hybrid 704 cultivar, application of nutrient solution with ammonium to nitrate ratio of 50:50 resulted in a significant 31% decrease in leaf chlorophyll a concentration compared to plants fed with a nutrient solution containing 25% ammonium (with the highest chlorophyll content). The leaf chlorophyll a concentration in single-cross 410 cultivar showed an increasing trend with increasing ammonium in the nutrient solution up to 25 percent, and then a decreasing trend with further increase in the ammonium proportion. Moreover, a 31.4% significant decrease in chlorophyll b concentration was observed in plants fed with a 50:50 ammonium to nitrate ratio compared to plants fed with a 37.5: 62.5 ammonium to nitrate ratio. The highest leaf carotenoid concentration was recorded in single-cross hybrid 704 cultivar and at 25:75 ammonium to nitrate ratio, which was 1.4 times higher than the leaf carotenoid concentration compared to plants fed with nutrient solution without ammonium. The highest relative leaf moisture content was observed in the plants nourished with ammonium to nitrate ratio of 25:75, which showed a significant 20% increase compared to the ammonium-free nutrient solution. The results also indicated that the application of 50% of nitrogen in the form of ammonium in the nutrient solution led to a significant decrease in the leaf surface area of maize. The highest shoot and root fresh weights were obtained in the plants nourished with 25:75 ammonium to nitrate ratio and in the single-cross hybrid 704 cultivar. The results showed that the highest water (solution) use efficiency based on fresh weight was recorded in plants fed with 25:75 ammonium to nitrate ratio and in the single-cross hybrid 704 cultivar. ConclusionBased on the results of the present study, the highest shoot and root fresh weights of both maize cultivars were obtained in plants fed with 25:75 ammonium to nitrate ratio. Given the limitations of water resources and rainfall, optimal use of minimum water to produce maximum agricultural crops must be cnsidered. According to the results of this research, application of nutrient solution with ammonium to nitrate ratio of 50:50 led to ammonium toxicity and a reduction in forage yield in both maize cultivars. Therefore, replacing 25% nitrate in the nutrient solution with ammonium and selecting the single-cross hybrid 704 cultivar (due to higher yield compared to single cross 410 cultivar) is recommended to achieve maximum fodder yield in soilless culture under conditions similar to this study.
Soil science
A. Sarabchi; H. Rezaei; F. Shahbazi
Abstract
Introduction
High-resolution satellite imagery data is widely utilized for Land Use/Land Cover (LULC) mapping. Analyzing the patterns of LULC and the data derived from changes in land use caters to the increasing societal demands, improving convenience, and fostering a deeper comprehension of the interaction ...
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Introduction
High-resolution satellite imagery data is widely utilized for Land Use/Land Cover (LULC) mapping. Analyzing the patterns of LULC and the data derived from changes in land use caters to the increasing societal demands, improving convenience, and fostering a deeper comprehension of the interaction between human activities and environmental factors. Although numerous studies have focused on remote sensing for LULC mapping, there is a pressing need to improve the quality of LULC maps to achieve sustainable land management, especially in light of recent advancements made. This study was carried out in an area covering approximately 8000 hectares, characterized by diverse conditions in LULC, geomorphology and pedology. The objective was to investigate the potential for achieving maximum differentiation and accurate mapping of land features related to LULC. Additionally, the study assessed the impact of various spectral indices on enhancing the results from the classification of Landsat 8 imagery, while also evaluating the efficacy of support vector machine (SVM) and maximum likelihood algorithms in producing maps with satisfactory accuracy and precision.
Materials and Methods
As an initial step, LULC features were identified through fieldwork, and their geographic coordinates were recorded using GPS. These features included various types of LULC, soil surface characteristics, and landform types. Following the fieldwork, 12 types of LULC units were identified. Subsequently, the LULC pattern in the study area was classified using the RGB+NIR+SWIR1 bands of Landsat 8, employing both SVM and maximum likelihood classifiers. To assess the impact of various spectral indices on improving the accuracy of the LULC maps, a set of vegetation indices (NDVI, SAVI, LAI, EVI, and EVI2), bare soil indices (BSI, BSI3, MNDSI, NBLI, DBSI, and MBI), and integrated indices (TLIVI, ATLIVI, and LST), and digital elevation model of study area were successively incorporated into the classification algorithms. Finally, the outcomes from the two classification algorithms were compared, taking into account the influence of the applied indexes. The classification process continued with the selected classifier and indices until reaching the maximum overall accuracy and kappa coefficient.
Results and Discussion
Field observations revealed that the study area could be categorized into 12 primary LULC units, including irrigated farms, flow farming, dry farming, traditional gardens (with no evident order observed among planted trees), modern gardens (featuring regular rows where soil reflectance is visible between tree rows), grasslands, degraded grasslands, highland pastures (covered by Astragalus spp., dominantly), lowland pastures (covered by halophyte plants), salt domes (with no or very poor vegetation), outwash areas (River channel with many waterways), and resistant areas. The results of image classification indicated that the performance of the SVM algorithm across different band combinations is superior to that of the maximum likelihood method. Using SVM resulted in an increase in overall accuracy and Kappa coefficient by 3-8% and 0.03-0.08, respectively. For the map generated using RGB+NIR+SWIR1 bands and employing SVM, overall accuracy and Kappa coefficient were determined to be 76.6% and 0.72, respectively. Among the vegetation indices used in the SVM algorithm, LAI had the most significant impact, increasing the classification accuracy by 2.64%. Among the soil indices, BSI and MBI indices demonstrated the best performance; with BSI increasing the classification accuracy by 1.95% and MBI by 1.64%. Among the integrated indices, LST and ALTIVI enhanced the classification accuracy by 2.75% and 2.35%, respectively. It should be noted that the inclusion of the digital elevation model did not significantly improve the classification accuracy when using the support vector machine algorithm; in fact, it led to a decrease in accuracy when applied to the maximum likelihood classification. The probable reason for this issue is the different nature of DEM data compared to the other input data, as well as the limitations of parametric statistical approaches to effectively integrating data from diverse sources. Finally, the classification process was executed using the three visible bands, NIR, and SWIR1, in conjunction with selected indices (LAI, BSI, MBI, LST, and ALTIVI). Results indicated that using these spectral indices significantly improved classification accuracy, particularly for the DF, DGL, MG, O, and IF land cover/use classes. The calculated accuracies for these classes increased by 11.62%, 18.57%, 20.06%, 29.39%, and 33.19% respectively. Consequently, the accuracy of the classification and the Kappa coefficient (using support vector machine algorithm) increased to 85.24% and 0.82, respectively.
Conclusion
In this research, we aimed to accurately map various land use/land covers by utilizing Landsat 8 imagery and incorporating three group of spectral indexes. Despite spectral interferences and overlaps among various phenomena related to LULC, the utilization of different spectral indices resulted in significant differentiation among LULC classes. Finally, considering the limitations of modelling in ENVI software, it is recommended to investigate the effectiveness of other models for classification in more specialized software, such as R.
Soil science
M. Malehmir Chegini; AHMAD GOLCHIN
Abstract
Introduction
Soil contamination with heavy metals significantly threatens both environmental and human health. Anthropogenic activities, including chemical fertilizers and pesticides, industrial processes, wastewater disposal, and mining, contribute to the accumulation of heavy metals in soil. Plants ...
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Introduction
Soil contamination with heavy metals significantly threatens both environmental and human health. Anthropogenic activities, including chemical fertilizers and pesticides, industrial processes, wastewater disposal, and mining, contribute to the accumulation of heavy metals in soil. Plants can then taken up these contaminants and enter the food chain, causing various health problems. Soil amendments such as biochar and activated carbon offer a promising strategy for reducing the mobility and bioavailability of heavy metals in soil. This study investigated the effectiveness of biochar and activated carbon derived from organic waste materials (wheat straw, walnut shells, and almond shells) in immobilizing lead (Pb), zinc (Zn), and cadmium (Cd) and promoting corn (Zea mays. L.) growth in a greenhouse setting using contaminated soil.
Materials and Methods
Three types of organic waste wheat straw, walnut shells and almond shells were pyrolyzed at two temperatures (300 °C and 500 °C) under oxygen-free conditions for two hours to produce six types of biochar. The resulting biochars were then activated with phosphoric acid at their respective production temperatures, yielding six types of activated carbon. These organic waste materials, biochar, and activated carbons were added to soil contaminated with lead, zinc and cadmium at four application rates (0, 2.5, 5, and 10% by weight) in triplicate, 4.5 Kg Pot-1. The pots were incubated for one month under controlled temperature and humidity to achieve a relative equilibrium. Following incubation, the concentration of available heavy metals in the treated and control soils was measured. Corn was then planted in the pots, and at the end of the growth period, plant growth parameters (dry weight of shoots and roots) and heavy metal concentrations in plant tissues were determined. The data were analyzed using a completely randomized factorial design, and treatment means were compared to each other and the control.
Results and Discussion
Increasing pyrolysis temperature resulted in increased biochar pH, electrical conductivity (EC), and ash content, while the percentage of organic carbon, C/N ratio, and cation exchange capacity (CEC) decreased. Activation with phosphoric acid lowered the pH, ash content, EC, and organic carbon content of the biochars, while increasing their CEC. Amending the soil with biochar significantly increased soil pH and EC, whereas activated carbon amendments decreased these parameters. All amendments (organic waste, biochar, and activated carbon) significantly reduced the concentration of available heavy metals in the soil. Activated carbon had the greatest effect on immobilization, while organic waste had the least. The lowest concentrations of lead, cadmium, and zinc extractable with DTPA were observed with the 500°C activated carbon derived from wheat straw at a 10% application rate, with values of 1.6, 4.5, and 464 mg kg-1 soil, respectively, representing reductions of 99.46%, 83.67%, and 63.96% compared to the control treatment. This treatment also resulted in the lowest heavy metal concentrations in both the aerial parts and roots of the corn plants. Specifically, the lowest concentrations of lead, zinc, and cadmium in the aerial parts were 71.67, 490.67, and 1.67 mg kg-1 dry weight, respectively, while in the roots, they were 206, 1095, and 20 mg kg-1 dry weight, respectively. The highest dry weights of the aerial parts and roots were also observed with this treatment and a 5% application rate, with values of 5.76 and 1.84 grams per pot, respectively. The lowest concentration of heavy metals in corn tissues was observed in treatments with activated carbon produced at 500 °C and applied at a rate of 10%.
Conclusion
This study demonstrates that activated carbon derived from organic waste materials can be an effective and sustainable method for remediating soil contaminated with heavy metals and promoting plant growth. However, the presence of detectable heavy metals in corn tissues following activated carbon application suggests that this approach may be best suited for soils with low to moderate contamination levels.
Soil science
D. Parmah; H.R. Chaghazardi; F. Mondany; A. Beheshti Ale Agha; D. Kahrizi
Abstract
IntroductionOptimum yield production under rainfed cultivation directly depends on the amount of rainfall and moisture storage in the soil. The tillage system directly influences soil moisture retention as well as the soil’s physical and chemical properties. Selecting the appropriate tillage system ...
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IntroductionOptimum yield production under rainfed cultivation directly depends on the amount of rainfall and moisture storage in the soil. The tillage system directly influences soil moisture retention as well as the soil’s physical and chemical properties. Selecting the appropriate tillage system can significantly impact crop yields. Oilseeds are particularly important among crops, representing the second-largest food reserve in the world after grains. These products are rich in fatty acids. Today, the oil extraction and production industry is one of the most strategic industries in most countries. Iran has vast arable land and favorable conditions for cultivating oilseeds. However, according to available statistics, over 80% of the country's oil needs are met through imports. Given the increasing demand for higher-quality oil products and the challenges posed by climate issues, such as recurring droughts, cultivating and developing crops with lower water requirements and greater resilience appears to be a promising solution. Implementing effective management practices and appropriate fertilizers aligned with conservation agriculture could help increase crop yields while maintaining and improving long-term soil quality. To explore the potential of oilseed cultivation, an experiment was conducted to examine the effects of tillage and fertilization on the yield and yield components of safflower under rainfed conditions. Materials and MethodsThis experiment was carried out as split plots based on random complete blocks design, with three replications under rainfed conditions. The treatments included tillage systems (conventional tillage, reduced tillage, and no-tillage) as the main factor and NPK fertilizer (a mixture of urea, triple superphosphate, and potassium sulfate) at four levels of zero, 33, 66, and 100% as a secondary factor. Potassium and phosphorus fertilization and 50% of nitrogen fertilizer were used at the same time as planting, and the remaining 50% of nitrogen fertilizer was used four months after planting. Each block had three main plots; the distance between each block was 3 meters, and between the main plots was 2 meters. In each main plot, four sub-plots were created, and the distance between the sub-plots was 1 meter. The area of the main plots was 21 × 15 meters, and the area of each sub-plot was 4.5 ×15 meters. The amount of seed used for safflower was 25 kg per hectare. The safflower seeds were sown in 5 rows and planted at a distance of 50 cm and a distance between plants of 10 cm. At all stages of planting, maintenance, and harvesting, agricultural management followed the traditional practices of the study area, as performed by the local farmers. The final sampling, or harvesting, was carried out manually at the physiological maturity stage. Before conducting variance analysis, a normality test was performed on the data. In this research, the LSD test was used to compare the mean at the 5% probability level, Excel software was used to draw graphs, and SAS 9.4 software was used to analyze the data. Results and DiscussionThe research showed that the traits examined, including leaf area index, dry matter content, thousand seed weight, seed yield, and biological yield, were affected by the tillage system, fertilizer, and their interaction effect. The highest safflower seed yield of 195.6 g/m2 was obtained from the fertilizer ratio of 33% and conventional tillage, and the lowest seed yield of 116.2 g/m2 was obtained from no-tillage and no fertilizer use. The results indicated that the conventional tillage system outperformed both reduced tillage and no-tillage systems. In reduced and no-tillage systems, the changes in the leaf area index of the safflower plant were similar, with the 100% fertilizer application under reduced tillage having a more pronounced effect compared to no-tillage. Additionally, in the absence of fertilizer in the no-tillage system, the leaf area index was lower. Fertilizer application increased the plant's biological yield, but its impact was greater under conventional tillage compared to reduced and no-tillage systems. Applying 33% of the required fertilizer in the conventional tillage system resulted in the highest biological yield for safflower, leading to a 94% increase in biological performance compared to the control. ConclusionIn most of the examined traits, the application of 33 and 66% of the fertilizer requirement caused the best results, and the 100% fertilizer ratio left adverse effects, which indicates the lower fertilizer requirement of this cultivar in the studied conditions compared to cultivars in other regions. Since the research was conducted in rainy years, conventional tillage was better than low tillage. It is suggested that this plant's production amount be evaluated under different irrigation conditions and moisture limitations so that tillage systems and management methods can be examined and selected more carefully.
Soil science
F. Rakhsh; A. Golchin; A. Beheshti Ale Agha
Abstract
Introduction
Soil texture is one of the most influential characteristics that affects the decomposition and retention of soil organic matter, as it directly or indirectly impacts the soil's physical, chemical, and biological properties. Soil clays play an important role in soil organic matter stability. ...
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Introduction
Soil texture is one of the most influential characteristics that affects the decomposition and retention of soil organic matter, as it directly or indirectly impacts the soil's physical, chemical, and biological properties. Soil clays play an important role in soil organic matter stability. Organic matter adsorbed on phyllosilicate clays is more resistant to microbial decomposition than organic matter that has not interacted with any mineral. Exchangeable cations through the influence of physical and chemical characteristics of the soil probably cause changes in the absorption and retention of organic matter. In previous studies, the effect of soil texture on organic matter retention has been investigated, but the impact of clay type and exchange cation has not been investigated. This study aimed to examine the effect of different contents of vermiculite and zeolite clays and exchange cations on the mineralization of organic nitrogen.
Materials and Methods
A factorial experiment was conducted in a completely randomized design with three replications to study the effect of the type and content of clay and the type of exchange cations on organic nitrogen dynamics. Experimental treatments include two types of clay (vermiculite and zeolite), four different levels of clay (0, 15, 30, and 45%), and three types of exchangeable cations (Na+, Ca2+, and Al3+). The experiment included 24 treatments and three replications. There were total of 72 experimental units. Artificial soil of 50 grams was prepared separately according to the amount and type of clay and the type of exchange cation. "Next, alfalfa plant residues were added to all samples at a rate of 5% w/w. After inoculating and air-drying the samples, the moisture content was adjusted to 60% of the field capacity (FC) using distilled water. To prevent excess water from affecting the final moisture readings, the samples were first air-dried, and then sufficient distilled water was added to each sample to achieve 60% of FC. The samples were then kept in the dark for 60 days at a temperature of 23 °C. Distilled water was added and sealed to the bottom of the incubation jars to keep the moisture content of the soil samples constant during incubation. The percentage of mineralized nitrogen, microbial biomass nitrogen, and the activity of acid and alkaline phosphatase and cellulase enzymes were determined in the prepared samples. The data were analyzed using ANOVA, and the means were compared using Duncan's Multiple Range Test (DMRT). Before applying ANOVA, the data's normality and variance homogeneity were checked using Kolmogorov- Smirnov and Levene tests, respectively. The SPSS software (Windows version 25.0, SPSS Inc., Chicago, USA) and SAS software (version 9.4, SAS Institute Inc., Cary, NC) were employed for data analysis.
Results and Discussion
The results of variance analysis of the data showed that the effect of the type and content of clay and the type of exchangeable cation on the percentage of mineralized nitrogen, microbial biomass nitrogen, and the activity of acid and alkaline phosphatase and cellulase enzymes were significant (p< 0.01). The results revealed that, regardless of the duration of the samples, with the increase in the amount of clay, the percentage of inorganic nitrogen and the activity of enzymes decreased, but the nitrogen of microbial biomass increased. The highest percentage of inorganic nitrogen was obtained 60 days after incubation of the samples and in clays saturated with calcium, and the lowest amount of these attributes was obtained 15 days after incubation of the samples and in clays saturated with aluminum. The results showed that nitrogen mineralization increased with the samples' incubation time. Also, the highest percentage of mineralized nitrogen, microbial biomass nitrogen, and enzyme activity were observed in soils with vermiculite.
Conclusion
The increase in the incubation duration enhanced the percentage of inorganic nitrogen. The percentage of mineralized nitrogen and microbial biomass nitrogen was higher in soils with vermiculite than in soils with zeolite. Moreover, regardless of the incubation duration of samples, with increasing clay content, the percentage of mineralized nitrogen and enzyme activity decreased, but with increasing clay nitrogen content, microbial biomass increased. The highest and lowest amounts of mineralized nitrogen and nitrogen of microbial biomass were measured in soils with calcium and aluminum, respectively. The results showed the effect of the clay type and content and the exchangeable cation type on organic nitrogen dynamics.
Soil science
F. Jannati; F. Sarmadian
Abstract
IntroductionResearch and development in high-potential agricultural areas are of great importance for ensuring the food needs of the population and livestock. Neglecting these regions can lead to increased food prices and food shortages, which can have a negative impact on the economy and public health. ...
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IntroductionResearch and development in high-potential agricultural areas are of great importance for ensuring the food needs of the population and livestock. Neglecting these regions can lead to increased food prices and food shortages, which can have a negative impact on the economy and public health. Land suitability maps provide essential information for agricultural planning and are vital for reducing land degradation and evaluating sustainable land use. The utilization of modern mapping techniques such as digital soil mapping and machine learning algorithms can significantly improve the accuracy of land suitability assessment and crop performance prediction. These methods have been widely employed as primary tools for mapping and evaluating land suitability in various regions worldwide. Materials and MethodsIn this study, a total of 288 soil profiles were utilized to compute the land suitability index for wheat, barley, and alfalfa crops. Various environmental variables were included, such as topographic factors derived from the digital elevation model and spectral indices obtained from Landsat 8 satellite imagery. Eight key factors, namely slope percentage, climate, texture, gypsum content, equivalent calcium carbonate, electrical conductivity (EC), and sodium absorption ratio (SAR), were identified as influential in the assessment of land suitability. To quantify the degrees of land suitability for the target crops, a parametric approach based on the square root method was employed. Moreover, the random forest machine learning model was utilized for spatial modeling, zoning mapping, and determining the significance of environmental variables in the land suitability evaluation process. By incorporating these comprehensive methodologies, a more detailed and accurate understanding of the land suitability for wheat, barley, and alfalfa cultivation can be achieved, facilitating informed decision-making in agricultural planning and land management strategies. Results and DiscussionThe spatial prediction results demonstrated the effectiveness of the random forest model in classifying land suitability for wheat, barley, and alfalfa. The model achieved high accuracy, with Kappa coefficients of 81%, 84%, and 85% for wheat, barley, and alfalfa, respectively. The overall accuracies were also impressive, reaching 86% for wheat, 88% for barley, and 89% for alfalfa. Analyzing the land suitability assessment results, it was found that barley had the highest land suitability class, covering a significant portion of 40% in class S1. Alfalfa followed closely with 35.5% of the total area, and wheat occupied 32% in the same class. Delving into the predictive environmental variables for barley, Diffuse, SHt, and MrVBF emerged as the most influential factors. These variables played a crucial role in assessing the suitability of land for barley cultivation. Similarly, for wheat, the variables Diffuse, MrVBF, and TWI were identified as significant indicators, contributing to the accurate prediction of wheat performance. Regarding alfalfa, the variables MrVBF, Diffuse, and Valley_depth stood out as the most important variables, providing valuable insights into land suitability for alfalfa cultivation. In general, the limiting factors for irrigated cultivation of these crops were primarily associated with soil properties. In the northern regions, soil texture was identified as a significant limiting factor, impacting the suitability of the land for crop cultivation. On the other hand, in the southern regions, soil characteristics such as the percentage of lime, gypsum, salinity, and alkalinity were recognized as the most influential limiting factors, affecting the suitability of the land for successful crop production. These findings provide valuable information for land planners, farmers, and decision-makers in determining suitable areas for wheat, barley, and alfalfa cultivation. By considering the identified influential factors and addressing the limiting soil properties, agricultural practices can be optimized to maximize crop productivity and ensure sustainable land use. ConclusionThe research aimed to evaluate land suitability for wheat, barley, and alfalfa crops under irrigation. Data selection focused on the most limiting factors for these crops. The model achieved acceptable predictions for wheat, barley, and alfalfa, with Kappa coefficients of 0.81, 0.85, and 0.84, and overall accuracies of 0.86, 0.89, and 0.88, respectively. Barley had the highest percentage of suitable land (40%), followed by alfalfa (39.5%) and wheat (32%). Soil constraints varied across the study area, including texture, stoniness, lime, gypsum, salinity, and alkalinity. The analysis identified 31 soil types, and the random forest model yielded a digital soil map with a Kappa coefficient of 0.76 and overall accuracy of 0.81. The findings support effective land management and agricultural planning.
Soil science
Z. Movahedi Rad; M. Hamidpour
Abstract
Introduction Recently, layered double hydroxides (LDHs) have attracted significant attention due to their various applications, particularly as slow-release fertilizers for essential plant nutrients. Several studies have reported the release of nitrate and phosphorus from LDHs. Additionally, micronutrients ...
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Introduction Recently, layered double hydroxides (LDHs) have attracted significant attention due to their various applications, particularly as slow-release fertilizers for essential plant nutrients. Several studies have reported the release of nitrate and phosphorus from LDHs. Additionally, micronutrients such as zinc (Zn), copper (Cu), and manganese (Mn) can be structurally incorporated into the metal hydroxide layers. Recent research indicates that LDHs have considerable potential for releasing these micronutrients. However, further studies are needed to enhance our understanding of the mechanisms and reactions of LDHs under different conditions. Currently, there is a lack of information regarding the divalent (M2+) to trivalent cation (M3+) ratios in LDHs and the influence of malic acid on the release of Zn, Mn, and magnesium (Mg) from these compounds. This study aimed to investigate the effects of malic acid and the ratio of M2+/M3+ on the kinetics release of Zn, Mn and Mg from Mg-Zn-Mn-Al-LDH intercalated with nitrate. Materials and MethodsAll chemicals used in this study including malic acid (C4H6O5), KCl, Zn(NO3)2.6H2O, Mn(NO3)2.4H2O, Mg(NO3)2.6H2O and Al(NO3).9H2O were of analytical grades, purchased from Chem-Lab or Merck Chemical Corporations. The solutions were made with the decarbonated ultrapure water (electrical resistivity = 18 MΩcm). The LDHs were synthesized by co-precipitation method at constant pH=9.2-9.6. Two types of LDHs were synthesized with varying the M+2(Zn+Mn+Mg)/M+3(Al) 3:1 and 4:1 in the precursor solution while being stirred vigorously in a nitrogen atmosphere. The pH was kept at 9.2-9.6 by adding volumes of 3 M NaOH. The crystals of LDH were ripened in the mixture for 2 h and after that, the precipitates were centrifuged at 3000 rpm for 20 min and washed several times with distilled water and placed in an oven at 70 °C for 8 h to dry. The chemical composition of the synthesized LDHs was determined by furnace atomic absorption spectrophotometry (SavantAA, GBC) after acid digestion. The physical, chemical, and morphological characteristics of the LDHs were determined using X-ray diffraction analysis (Panalytical x Pert ProX-ray diffractometer), Fe-SEM (Sigma VP), FT-IR (Nicolet iS10 spectrometer), and BET (BELSORP Mini II) techniques. A batch study was done to determine the effect of different ratios of M2+/M3+ in LDHs and the effect of malic acid on release of Zn, Mn, and Mg from LDH (3:1) and LDH (4:1). Briefly, 0.01 g of synthesized LDH were put in a centrifuge tube mixed with 10 ml background electrolyte (KCl 0.01 M) and 1.25 mM malic acid in initial pH=6-7 and constant temperature (25±0.5 °C). Blank samples (without ligand) were also considered. Suspensions were shaken at periods ranging from 5 to 720 min agitation (180 rpm). Then, the supernatant solution was separated using a centrifuge at a speed of 4000 rpm for 20 min. Zn, Mn, and Mg concentrations in supernatants solutions were determined by graphite furnace atomic absorption spectrophotometry. The effect of pH in the range of 5 to 10 on the release of Zn, Mn, and Mg from LDH was also studied. Two equations (pseudo-second-order and Elovich) were used to fit the kinetics data. Results and DiscussionThe results showed that the calculated molar ratio of divalent cation to trivalent cation was similar to their molar ratio in the solution prepared for the synthesis of LDH samples. The X-ray diffraction patterns of LDH (3:1) and LDH (4:1) samples showed the existence of strong and sharp peaks for 003 and 006 plates. Accordingly, the reflections of the 003 and 006 plates revealed the layered structure of the synthesized LDH materials. Two bands of FT-IR spectrums around 3480 and 1620 cm-1 for all synthesized LDH materials designated stretching vibrations of the O-H group of hydroxide layers and the interlayer water molecules. The sharp characteristic band around 1382 cm−1 in LDH (3:1) and band around 1354 cm-1 in LDH (4:1) was attributed to the antisymmetric stretching mode of nitrate anion in LDH. The specific surface area of LDH (3:1) and LDH (4:1) were 5.50 m2g-1 and 16.54 m2g-1 respectively. The average pore diameters in LDH (3:1) and LDH (4:1) were 1.92 nm and 2.55 nm, respectively. Time-dependent cumulative release of Zn, Mn, and Mg from LDH (3:1) and LDH (4:1) in the presence and absence of malic acid was investigated. Time-dependent Zn, Mn, and Mg release from LDH (3:1) and LDH (4:1) was accelerated in the presence of malic acid. The Zn, Mn, and Mg release from the LDHs was likely to be separated into two stages. In the initial stage from 0 to 60 min, the release rate of Zn, Mn, and Mg was rapid, then either remained constant or slightly enhanced during 60–720 min. In this research, among the non-linear models used to determine the release kinetics of Zn, Mn, and Mg, the result with the highest R2 values was chosen. The R2 values were 0.91–0.99, 0.93–0.99, 0.93–0.99, 0.89-0.99, and 0.55–0.86 for pseudo-first-order, pseudo-second-order, Elovich, power function, and parabolic diffusion, respectively. So, pseudo-second-order and Elovich models were used to analyze kinetic data. The amounts of release of Zn, Mn and Mg were higher from LDH (4:1) than from LDH (3:1) because of greater specific surface area, volume, and pore diameter in LDH (4:1). A comparison of metal release versus time profiles exhibited that dissolution was greatly dependent on the pH. ConclusionThe results of this research indicated that the release of Zn, Mn, and Mg from layered double hydroxides (LDHs) was influenced by factors such as time, ligand, solution pH, and the type of LDH. According to the kinetics models fitted to the experimental data, the release rate of Zn, Mn, and Mg from LDH (4:1) was higher than that from LDH (3:1). In both types of LDHs, the presence of malic acid significantly increased both the rate and amount of Zn, Mn, and Mg release compared to the absence of malic acid. While this study demonstrated that varying the ratios of divalent to trivalent cations can influence the amount and rate of Zn and Mn release, further greenhouse studies are required to confirm the effectiveness of LDH as a slow-release fertilizer in calcareous soils.
Soil science
Z. Barati; H.R. Owliaie; E. Adhami; M. Najafi-Ghiri
Abstract
IntroductionRecently, layered double hydroxides (LDHs) have attracted significant attention due to their variousapplications, particularly as slow release fertilizers for essential plant nutrients. Several studies have reported therelease of nitrate and phosphorus from LDHs. Additionally, micronutrients ...
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IntroductionRecently, layered double hydroxides (LDHs) have attracted significant attention due to their variousapplications, particularly as slow release fertilizers for essential plant nutrients. Several studies have reported therelease of nitrate and phosphorus from LDHs. Additionally, micronutrients such as zinc (Zn), copper (Cu), andmanganese (Mn) can be structurally incor porated into the metal hydroxide layers. Recent research indicates thatLDHs have considerable potential for releasing these micronutrients. However, further studies are needed toenhance our understanding of the mechanisms and reactions of LDHs under diff erent conditions. Currently, thereis a lack of information regarding the divalent (M 2+2+) to trivalent cation (M 3+3+) ratios in LDHs and the influence ofmalic acid on the release of Zn, Mn, and magnesium (Mg) from these compounds. This study aimed toinvesti gate the effects of malic acid and the ratio of M 2+2+/M 3+ on the kinetics release of Zn, Mn and Mg from MgZn Mn Al LDH intercalated with nitrate nitrate.Materials and MethodsAll chemicals used in this study including malic acid (C4H6O5), KCl, Zn(NO3)2.6H2O, Mn(NO3)2.4H2O, Mg(NO3)2.6H2O and Al(NO3).9H2O were of analytical grades, purchased from Chem-Lab or Merck Chemical Corporations. The solutions were made with the decarbonated ultrapure water (electrical resistivity = 18 MΩcm). The LDHs were synthesized by co-precipitation method at constant pH=9.2-9.6. Two types of LDHs were synthesized with varying the M+2(Zn+Mn+Mg)/M+3(Al) 3:1 and 4:1 in the precursor solution while being stirred vigorously in a nitrogen atmosphere. The pH was kept at 9.2-9.6 by adding volumes of 3 M NaOH. The crystals of LDH were ripened in the mixture for 2 h and after that, the precipitates were centrifuged at 3000 rpm for 20 min and washed several times with distilled water and placed in an oven at 70 °C for 8 h to dry. The chemical composition of the synthesized LDHs was determined by furnace atomic absorption spectrophotometry (SavantAA, GBC) after acid digestion. The physical, chemical, and morphological characteristics of the LDHs were determined using X-ray diffraction analysis (Panalytical x Pert ProX-ray diffractometer), Fe-SEM (Sigma VP), FT-IR (Nicolet iS10 spectrometer), and BET (BELSORP Mini II) techniques. A batch study was done to determine the effect of different ratios of M2+/M3+ in LDHs and the effect of malic acid on release of Zn, Mn,and Mg from LDH (3:1) and LDH (4:1). Briefly, 0.01 g of synthesized LDH were put in a centrifuge tube mixed with 10 ml background electrolyte (KCl 0.01 M) and 1.25 mM malic acid in initial pH=6-7 and constant temperature (25±0.5 °C). Blank samples (without ligand) were also considered. Suspensions were shaken at periods ranging from 5 to 720 min agitation (180 rpm). Then, the supernatant solution was separated using a centrifuge at a speed of 4000 rpm for 20 min. Zn, Mn, and Mg concentrations in supernatants solutions were determined by graphite furnace atomic absorption spectrophotometry. The effect of pH in the range of 5 to 10 on the release of Zn, Mn, and Mg from LDH was also studied. Two equations (pseudo-second-order and Elovich) were used to fit the kinetics data.Results and DiscussionThe results showed that the calculated molar ratio of divalent cation to trivalent cation was similar to their molar ratio in the solution prepared for the synthesis of LDH samples. The X-ray diffraction patterns of LDH (3:1) and LDH (4:1) samples showed the existence of strong and sharp peaks for 003 and 006 plates. Accordingly, the reflections of the 003 and 006 plates revealed the layered structure of the synthesized LDH materials. Two bands of FT-IR spectrums around 3480 and 1620 cm-1 for all synthesized LDH materials designated stretching vibrations of the O-H group of hydroxide layers and the interlayer water molecules. The sharp characteristic band around 1382 cm−1 in LDH (3:1) and band around 1354 cm-1 in LDH (4:1) was attributed to the antisymmetric stretching mode of nitrate anion in LDH. The specific surface area of LDH (3:1) and LDH (4:1) were 5.50 m2g-1 and 16.54 m2g-1 respectively. The average pore diameters in LDH (3:1) and LDH (4:1) were 1.92 nm and 2.55 nm, respectively. Time-dependent cumulative release of Zn, Mn, and Mg from LDH (3:1) and LDH (4:1) in the presence and absence of malic acid was investigated. Time-dependent Zn, Mn, and Mg release from LDH (3:1) and LDH (4:1) was accelerated in the presence of malic acid. The Zn, Mn, and Mg release from the LDHs was likely to be separated into two stages. In the initial stage from 0 to 60 min, the release rate of Zn, Mn, and Mg was rapid, then either remained constant or slightly enhanced during 60–720 min. In this research, among the non-linear models used to determine the release kinetics of Zn, Mn, and Mg, the result with the highest R2 values was chosen. The R2 values were 0.91–0.99, 0.93–0.99, 0.93–0.99, 0.89-0.99, and 0.55–0.86 for pseudo-first-order, pseudo-second-order, Elovich, power function, and parabolic diffusion, respectively. So, pseudo-second-order and Elovich models were used to analyze kinetic data. The amounts of release of Zn, Mn and Mg were higher from LDH (4:1) than from LDH (3:1) because of greater specific surface area, volume, and pore diameter in LDH (4:1). A comparison of metal release versus time profiles exhibited that dissolution was greatly dependent on the pH.ConclusionTheresults of this research indicated that the release of Zn, Mn, and Mg from layered double hydroxides(LDHs) was influenced by factors such as time, ligand, solution pH, and the type of LDH. According to thekinetics models fitted to the experimental data, the release rate of Zn, Mn, and Mg from LDH (4:1) was higherthan that from LDH (3:1). In both types of LDH s , the presence of malic acid significantly increased both the rateand amount of Zn, Mn, and Mg release compared to the absence of malic acid. While this study demonstratedthat varying the ratios of divalent to trivalent cations can influence the amount and rate of Zn and Mn release,further greenhouse studies are required to confirm the effectiveness of LDH as a slow release fertilizer incalcareous soils.
Soil science
J. Sadeghi; A. Lakzian; A. Halajnia; M. Alikhani Moghaddam
Abstract
Introduction
The rapid growth of technology, industry, and development of cities has led to an increase in heavy metal pollution in freshwater sources and greywater across the world. The use of different adsorbents in order to remove some heavy metals from aquatic environments is a topic that has been ...
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Introduction
The rapid growth of technology, industry, and development of cities has led to an increase in heavy metal pollution in freshwater sources and greywater across the world. The use of different adsorbents in order to remove some heavy metals from aquatic environments is a topic that has been addressed many times in different studies. However, the use of inexpensive absorbents with high adsorption capacity and high efficiency is the priority of many researchers especially when they are discussing the removal of heavy metals from the aquatic environment. Nanomaterials by having exceptional properties such as high efficiency of adsorption, high specific surface area, and fast adsorption can be used to remove metal pollutants from aquatic environments. Carbon dot (CD), among various nanomaterials (carbon-based nanomaterials (CNM), including carbon nanotubes (CNTs), graphene) are suitable adsorbents for heavy metals removal due to their specific surface area and many binding sites. Carbon dots are nanoparticles that lack a specific dimension and fall under the category of carbon nanomaterials, measuring over 10 nm in size. They possess various qualities, including being environmentally friendly, simple to create, highly compatible with living organisms, stable, and capable of switching emission on and off based on the excitation wavelength. Additionally, they can be customized for specific uses due to their high carbon content, which can reach up to 99.9%. These characteristics have generated significant interest among researchers in various fields. In this study, the influence of the fungal carbon dots on the adsorption capacity and kinetics, isotherms, and thermodynamics of lead was investigated.
Materials and Methods
Alternaria alternata provided by the Department of Plant Protection at Ferdowsi university of Mashhad. It was recultured and fungal exopolysaccharide was extracted and then was converted into carbon dot using the hydrothermal method. Fungal exopolysaccharide autoclaved in a Teflon container at a temperature of 200 °C. Lead adsorption of synthesized fungal carbon dots was investigated. Lead adsorption tests by fungal carbon dots were performed in laboratory conditions. Lead concentrations (100, 200, 300, 400, 500, 750 and 1000 mg L-1), contact time (5, 10, 15, 20, 25, 30 and 60 minutes), pH (2, 4, 6, 7, 8, 9, 10 and 11), amount of carbon dots (nanosorbent) (50, 100, 200, 300, 400, 500, 750 and 1000 mg), ionic strength of the solution (0.1, 0.01 and 0.001 M potassium chloride) and solution temperature (25, 30, 35, 40 and 45 °C) was considered for kinetic tests. The data obtained from the kinetic tests were fitted using non-linear regression analysis using Statistica 7.0 software with the kinetic models of intraparticle diffusion, Lagergren (pseudo-first order) and pseudo-second-order. Thermodynamic results were calculated from the data of lead adsorption isotherms at temperatures of 25, 35 and 45 °C. Thermodynamic parameters to analyze the effect of temperature on metal adsorption, such as free energy change, enthalpy change and entropy change, were estimated using thermodynamic equations.
Results and Discussion
The initial lead concentration had a great effect on the adsorption rate it by carbon dot, and the highest and lowest percentage of lead adsorption with values of 90.65 and 44.2% were observed in two concentrations of 300 and 1000 mg L-1 of lead, respectively. With the increase of pH up to 8, the amount of lead adsorption by fungal carbon dot increased significantly. However, with further increase in pH, this trend was reversed and the amount of adsorption decreased. The results showed that lead adsorption by carbon dot increased with the decrease of potassium chloride molarity. By increasing the amount of carbon dot in the solution, the amount of lead adsorption increased, and the highest adsorption was observed at the concentration of 300 mg L-1 of carbon dot. The results of the experiment also showed that with increase in temperature, the adsorption rate increased at first and then decreased. Based on these results, as the contact time between the absorbent and lead increased, the amount of adsorption by the carbon dots also increased. The maximum adsorption was observed at 25 minutes, which was considered the equilibrium time. As shown in the results, the pseudo-second-order model shows the kinetics of Pb adsorption better than the two pseudo-first-order models and intraparticle diffusion. In this model, R2 values are between 0.9989 and 0.9994, and Qe is almost equal to the equilibrium value. According to these results, the decrease of values DG° with the increase in temperature means that the adsorption of lead increases with the increase in temperature, which shows that the adsorption process is more favorable with the increase in temperature, or in other words, it is a spontaneous reaction. Also, the positivity of the reaction enthalpy value (DH°) shows the endothermic nature of the adsorption process. The positivity of the entropy value (DS°) indicates the increase of disorder of the system between the adsorbent material and the solution during the process of lead adsorption by the carbon dot.
Conclusion
In total, the results showed that the carbon dot is a very good absorbent for removing lead from the water environment. In the experimental condition when the initial concentration of lead was 300 mg L-1, temperature was 25 °C, adsorbent concentration was 0.3 g L-1, reaction time was 25 minutes, and pH 8, the amount of lead adsorption increased significantly. It seems that fungal carbon dot is a safe and relatively cheap adsorbent and suitable for removing lead metal from the solution environment.
Soil science
Z. Mosleh Ghahfarokhi; A. Azadi
Abstract
Introduction
Soil properties play a crucial role as they determine the soil's suitability for different types of plant growth, ecosystems, and biota functioning. They have a significant impact on nutrient cycling, carbon sequestration, and soil management. Digital Soil Mapping (DSM) is a process aimed ...
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Introduction
Soil properties play a crucial role as they determine the soil's suitability for different types of plant growth, ecosystems, and biota functioning. They have a significant impact on nutrient cycling, carbon sequestration, and soil management. Digital Soil Mapping (DSM) is a process aimed at delineating soil properties. Soil sampling for DSM serves as a fundamental step in improving prediction accuracy and is crucial for incorporating variability in terms of environmental covariates. Conditioned Latin Hypercube (CLH) sampling is a technique utilized to generate a sample of points from a multivariate distribution conditioned on one or more covariates. Numerous researchers (Ramirez-Lopez et al., 2014; Adhikari et al., 2017; Zhang et al., 2022) have endorsed this approach in their studies, following its inception by Minasny and McBratney in 2006. However, there has been limited research to date on the impact of the Latin hypercube method's random sample selection process on the accuracy of resulting maps. Hence, the central question remains: Is the Latin hypercube sampling method, which is currently widely adopted, always a dependable approach in this field?
Materials and Methods
The study area covers longitudes 50°35'47'' to 51°29'' east and latitudes 31°36''31'' to 32°15'48'' north in Borujen city, Chaharmahal, and Bakhtiari Province. The region, with an average elevation of 2338 meters above sea level, receives an annual rainfall of 250 millimeters and maintains an average temperature of 11.5 degrees centigrade. In this investigation, inherited data from soil studies were utilized, consisting of 250 samples distributed across the study area. In this research, the studied characteristics included percentage of equivalent calcium carbonate, clay, and soil organic carbon at a depth of 0 to 30 cm. Land component variables were extracted using the Alus Palsar digital elevation model with a spatial resolution of 12.5 meters. In the initial stage, digital maps of equivalent calcium carbonate, clay, and soil organic carbon were generated using the support vector machine method. The modeling process proceeded until a highly accurate model was achieved, with the root mean square error percentage (RMSE%) being less than 40. The Latin hypercube approach was utilized for sample design, with 500 repetitions in this study. After selecting sampling points for each run using the Latin hypercube method, these points were mapped onto a detailed map, and the corresponding feature values were retrieved. The final map was created based on the extracted points. Subsequently, the latin hypercube approach was employed to generate soil property maps for each selected dataset. Validation was conducted using criteria such as the coefficient of explanation, root mean square error, and root mean square error in multiple iterations to ensure the accuracy of the generated maps.
Results and Discussion
The results distinctly illustrates the varied selection of sampling positions with each implementation of the Latin hypercube method. It is important to note that there may be some overlaps in different implementations. Consequently, the primary question arises: Is a one-time execution of the Latin hypercube sufficient for selecting study points? The findings indicate that the support vector machine model achieves satisfactory accuracy for all the examined characteristics. In the studied area, the environmental factors such as slope and elevation were identified as a significant predictors for estimating percentage of equivalent calcium carbonate.
Conclusion
In the present study, the accuracy of the latin hypercube method was assessed for selecting sampling location for digital soil mapping endeavors in Chaharmahal and Bakhtiari Province. Given the impracticality of collecting numerous field samples to evaluate the soil sampling method, this research aimed to employ simulation methods based on highly accurate maps for this purpose. The results indicate that the different outputs of the Latin hypercube method influence the accuracy of modeling, although this effect is also influenced by the specific feature under investigation and the extent of its variability within the study area. Considering that the Latin hypercube method is based on the principle that samples are randomly selected in each class of environmental parameters, it is suggested that future studies using this method should account for this principle. Adequate consideration should be given, and the selection of sampling locations should rely on multiple implementations of the Bhattacharya distance method to ensure robustness and reliability.
Soil science
H. Asgari; M. Barani Motlagh; S.A. Movahedi Naeini; A. Babaei
Abstract
Introduction
Wheat is considered the most important grain and one of the vital food products in Iran. After nitrogen, phosphorus is the most important nutrient required by plants and holds a high priority for the growth, yield and quality of plants. However, due to the introduction of phosphorus in ...
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Introduction
Wheat is considered the most important grain and one of the vital food products in Iran. After nitrogen, phosphorus is the most important nutrient required by plants and holds a high priority for the growth, yield and quality of plants. However, due to the introduction of phosphorus in various reactions in the soil, a small amount of consumed phosphorus fertilizer is removed by the plant and the rest of it is left in a non-absorbable form in the soil. The efficiency of using phosphorus fertilizers and the availability of this nutrient is considered as a limiting factor for the production of agricultural products in calcareous soils with alkaline reaction of Iran. Since graphene and its oxidized form, with large amounts of active oxygen groups and high specific surface area, have been proposed by many studies as non-toxic and biocompatible materials in the production of compounds with improved efficiency of using nutrient, therefore to increase the efficiency of phosphorus consumption in soil, in this study, phosphorus was loaded on graphene oxide (GO-P). The present study aims to assess the influence of this compound as a source of phosphorus and its mixing with triple superphosphate fertilizer (GO-P-TSP) compared to triple superphosphate soluble fertilizer (TSP) on the amount of water retention of fertilizers in soil and phosphorus concentration in aerial parts of wheat plant.
Methods and Materials
Graphene oxide was prepared based on the modified Hamers method. Then graphene oxide was adjusted to certain pH and iron sulfate as a source of iron ions was added to the graphene oxide suspension with vigorous stirring. The mixture was stirred for one hour and then centrifuged for 30 minutes. Then the supernatant was removed and the residue of the compound was dry frozen. In the next step, pH was adjusted with sodium hydroxide (NaOH) solution. Then a certain weight of potassium dihydrogen phosphate salt (KH2PO4) was added to the above suspension. The mixture was stirred for one hour and centrifuged for 30 minutes. After centrifugation, the supernatant was removed and the remains of the phosphorus composition based on graphene oxide were dry frozen. Loading tests were performed in three replicates. pH, EC, bulk density, total concentration of phosphorus and iron and X-ray diffraction spectroscopy (EDS) analysis were measured in the sample of phosphorus composition based on graphene oxide. Then three fertilizer formulations were selected, which included (1) triple superphosphate fertilizer, (2) synthesized phosphorus fertilizer based on graphene oxide, and (3) mixing graphene oxide-phosphorus compound with triple superphosphate fertilizer in a ratio of 50:50% phosphorus.
To investigate the water retention behavior of fertilizers in the soil, dried samples of the three studied fertilizer formulations was added into a sandy soil completely and weighed. At the same time, dried sandy soil without fertilizer was placed in another beaker as a control. Then each beaker was added distilled water and weighed. The beakers were weighed once every three days at room temperature until they reached constant mass. The water-retention behavior of the soil was calculated.
In order to investigate the effect of three fertilizer formulations on phosphorus availability, soil with low amount of phosphorus was selected and physical and chemical properties of the soil sample were measured at a depth of 0-30 cm. A greenhouse experiment on wheat planting was conducted using a randomized complete design with 3 replications. The treatments included three fertilizer formulations at three fertilization levels (10, 15, and 20 mg kg-1) with 3 replications. The control treatment was performed without phosphorus fertilizer. Plants were harvested 72 days after planting, washed with distilled water and dry with tissue paper. The samples were air-dried and then oven dried at 70˚C to a constant weight in a forced air-driven oven. After harvesting, the weight of fresh and dry matter and phosphorus concentration in the soil and aerial parts of the plant were measured. Statistical data were analysed using SAS software (9.4) and the mean values were compared using LSD tests (at 1 and 5% level).
Results and Discussion
The composition of phosphorus based on graphene oxide (GO-P) in powder form had 35.5% of total P2O5, 31.1% of soluble in water P2O5, 19.6 of total iron and 15.28% of total potassium. The result of EDS analysis confirmed the loading of phosphorus on graphene oxide. The pH of the phosphorus composition based on graphene oxide was 5.8, approximately 2.5 units higher than triple superphosphate fertilizer. The bulk density of the compound (GO-P) was significantly lower than triple superphosphate fertilizer. The EC of the compound (GO-P) was similar to the EC of the triple superphosphate fertilizer. Soil water retention with synthesized phosphorus fertilizer based on graphene oxide (GO-P) was higher than soil (control) and other compounds added to soil. Experimental results showed that the addition of prepared fertilizer formulas (GO-P and GO-P-TSP) increased water retention in the soil for a longer period of time, while in the soil without adding fertilizer and triple superphosphate treatment, respectively, from 10 and 11 days, the absorbed water completely evaporated. Therefore, the combination of soil with GO-P and GO-P-TSP compared to the soil without fertilizer and the combination of soil with triple super phosphate (TSP) fertilizer had better water retention behavior. The greenhouse experiment results of wheat planting showed that all treatments were significant (P<0.01). Among all the treatments and measured levels, the control treatment showed the lowest value. The highest concentration of phosphorus in aerial parts of wheat (0.31%) and in soil after harvesting (9.5 mg kg-1), fresh (10.6 g per pot) and dry weight (2.03 g per pot) of aerial wheat plants were related to the treatment of phosphorus compounds based on graphene oxide at the level of 20 mg kg-1.
Conclusion
The highest concentration of phosphorus in aerial parts of wheat was related to the treatment of phosphorus compound based on graphene oxide at the level of 20 mg kg-1. Therefore, with more research in the future to produce "nutritious plants" in sustainable, efficient and flexible agricultural systems, we can benefit from technologies based on carbon materials.
