Soil science
fatemeh jannati; Fereydoon sarmadian
Abstract
AbstractIntroduction:Research 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 ...
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AbstractIntroduction:Research 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 Methods:In 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 incorporated, including 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 Discussion:The 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.Conclusion:The 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
Fatemeh Rakhsh; Ahmad Golchin; Ali Beheshti Ale Agha
Abstract
Introduction
Soil texture is one of the most influential characteristics of soils that affect the decomposition and retention of soil organic matter because it directly or indirectly affects soil's physical, chemical, and biological properties. Soil clays play an important role in soil organic matter ...
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Introduction
Soil texture is one of the most influential characteristics of soils that affect the decomposition and retention of soil organic matter because it directly or indirectly affects 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 with 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. Then, alfalfa plant residues were added to all the samples at 5% w/w. After adding the inoculum and air drying the samples, the humidity of the samples reached 60% of the field capacity (FC) using distilled water (We first air-dried the samples to prevent the excess water from causing an error in the final moisture, and then we added enough distilled water to each sample to reach 60% of FC). They were 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 clay.
Conclusion
The increase in the incubation duration increased the percentage of inorganic nitrogen. The percentage of mineralized nitrogen and microbial biomass nitrogen was higher in soils with vermiculite clay than in soils with zeolite clay. 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
zahra movahedirad; Mohsen Hamidpour
Abstract
Introduction
Recently, layered double hydroxides (LDH) have attracted considerable attention. LDHs have found applications in numerous cases particularly slow-release fertilizers for essential nutrients for plants. Several studies have reported the release of nitrate and phosphorus from LDHs. The metal ...
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Introduction
Recently, layered double hydroxides (LDH) have attracted considerable attention. LDHs have found applications in numerous cases particularly slow-release fertilizers for essential nutrients for plants. Several studies have reported the release of nitrate and phosphorus from LDHs. The metal hydroxide layer can structurally incorporate micronutrients such as Zn, Cu, and Mn. According to recent research, LDHs have a suitable potential for releasing micronutrients. No information regarding ratios M2+/M3+ in LDHs and the influence of malic acid on the release of Zn, Mn, and Mg from LDHs is available. This study aimed to investigate the effects of malic acid and the ratio of divalent cation (M2+) to trivalent cation (M3+) on the kinetics release of Zn, Mn and Mg from Mg-Zn-Mn-Al-LDH intercalated with nitrate.
Materials and Methods
All 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 hours 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 minutes. Zn, Mn, and Mg concentrations in supernatant 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 Discussion
. The results showed that the calculated molar ratio of divalent cation to trivalent cation is 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 show the existence of strong and sharp peaks for 003 and 006 plates. Accordingly, the reflections of the 003 and 006 plates reveal 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 designate 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) is 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). On the other hand, the presence of divalent cations in this structure has increased its instability. A comparison of metal release versus time profiles exhibited that dissolution was greatly dependent on the pH.
Conclusions
The results of this research showed that the release of Zn, Mn, and Mg from LDHs was dependent on time, ligand, solution pH, and the type of LDH. Based on the results of fitting the kinetics models to the experimental data, the release rate of Zn, Mn, and Mg from LDH (4:1) was higher than LDH (3:1). In both types of LDH, the presence of malic acid led to an increase in the rate and amount of release of Zn, Mn, and Mg compared to the absence of malic acid. Although the results of this research showed that it is possible to influence the amount and rate of release of Zn and Mn by synthesizing these compounds in different ratios of divalent to trivalent cations, to confirm the efficiency of LDH as a slow-release fertilizer in calcareous soils, greenhouse studies are needed.
Soil science
Zeinab Barati; Hamidreza Owliaie; ebrahim adhami; Mahdi Najafi Ghiri
Abstract
Introduction
Zagros oak forest ecosystem is one of the largest forest ecosystems under destruction in Iran, which is of great importance in terms of water and soil protection. Moisture stress in recent years has caused the deterioration of these forests in a wide area. Iranian oak (Quercus brantii Lindlb.) ...
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Introduction
Zagros oak forest ecosystem is one of the largest forest ecosystems under destruction in Iran, which is of great importance in terms of water and soil protection. Moisture stress in recent years has caused the deterioration of these forests in a wide area. Iranian oak (Quercus brantii Lindlb.) is the main tree species forming these forests. Potassium (K) is considered to be the most important nutrient cation in terms of its quantity in plant tissue and its physiological and biochemical functions. Soil tests measure the quantity of a nutrient element that is extracted from soil by a particular extracting solution. Over the years, many different soil testing methods and extracting solutions were evaluated to identify a technique that provides the most reliable prediction of crop yield response to nutrient application. It was determined that some soil testing procedures are best suited for particular soil types and climatic regions. There has been no research on the general status of K in the soil of Zagros forests, related to oak trees. It is important to introduce appropriate K extractants for extracting available K in these soils. Therefore, this research was carried out to achieve the mentioned goals in some forest areas of this Province.
Materials and Methods
Ten forest areas with dominant coverage of oak trees were selected in different parts of Kohgiluyeh and Boyerahmad Province. The physiochemical properties of the soil samples were determined based on standard methods. Soil pH, texture, electrical conductivity, calcium carbonate equivalent (CCE), organic carbon, and cation exchange capacity (CEC) were identified. The content of K present in different forms was determined by standard methods. Solution K was measured in the saturated extract. Exchangeable K was determined by extraction of 5 g soil sample with 20 mL 1 M NH4OAc (pH 7) for 5 min. Nitric acid-extractable K was measured by extraction of 2.5 g soil sample with 30 mL of boiling 1.0 M HNO3 for 1 h. Non-exchangeable K was calculated as the difference between HNO3-extractable K and NH4OAc-extracteable K. Total K was determined following digestion of 0.5 g soil sample with 10 mL of 48% HF and 1 mL of aqua regia. The 12 extracting solutions were 1M NaCl, 2M NaCl, 0.01M CaCl2, Morgan, AB-DTPA, 1M NH4OAC, 0.25M NH4OAC, 1M MgOAC, 1M NaOAC, 2M HCl, 0.1M HNO3, and 0.025M H2SO4. The K content of leaf samples was determined in 1g of each sample. The samples were dried and then ashed in 450°C for 4 h. 2M HCl was used to digest the samples. Potassium was measured on all filtrated extracts using a Corning 405 flame photometer.
Results and Discussion
The soils are all calcareous (average of 42.9 and 44.7% CCE in surface and subsurface, respectively), with pH in range of 7.0-7.8. The textural classes were sandy clay loam, clay loam, and clay. The range of soluble potassium is between 4.8 to 32.7 with an average of 15.4 mgkg-1, exchangeable potassium from 65.1 to 364 (with an average of 247 mgkg-1, non-exchangeable potassium from 106 to 876 with an average of 515 mgkg-1, structural potassium was from 761 to 7322 with an average of 4026 mgkg-1and total potassium was from 1051 to 8110 with an average of 4493 mgkg-1. Soluble, exchangeable, non-exchangeable, and structural potassium were 0.49, 9.6, 12.1, and 77.8%, of the total K, respectively. Among the 12 tested methods, 1.0 mol/L NH4OAC extracted the highest amount of K (mean 229.3 mgkg-1, ranging 64.9-384.2 mgkg-1) and 1.0 mol/L MgOAC removed the lowest amount of K (mean 53.0 mgkg-1, ranged 19.1-88.0 mgkg-1). Correlation coefficients between K extracted by 12 extractants were positive and significant. Maximum correlation between K leaf and extracted soil K was noticed in AB-DTPA, 0.25M NH4OAC, 1M NaCl, and Morgan-Wolfe (r=0.60, 0.59, 0.56, and 0.55, respectively) and the minimum correlation was noticed in 2M HCl and 0.025 M H2SO4 (r= 0.41 and 0.44, respectively). The amount of potassium in oak leaves (in the range of 0.65% to 1.18%) showed a significant correlation with exchangeable potassium in the soil. The amount of potassium in 50% of the oak leaf samples was less than the critical limit (1%). As a general result, 1M NaCl and 0.25M NH4OAC extractants are recommended for extracting potassium, due to greater correlation, simplicity of the method, and economic considerations.
Conclusion
The results of this research showed that the range of the values of different forms of potassium in different parts of the province had a relatively large difference (6 and 8 times difference in exchangeable and non-exchangeable potassium values). The amounts of available forms of potassium in the western regions of the province with less rainfall were in most cases higher than the more humid eastern regions. The average amount of exchangeable potassium in 60% of the studied areas was less than the critical limit of 250 mgkg-1 soil. Also, the average amount of leaf K in 50 percent of the samples was less than the critical level. Considering the great importance of potassium in the nutrition of oak trees and dealing with environmental stress, especially the shortage of soil moisture, it is recommended to pay more attention to the conditions of this element in the soil of the forest areas of the province. Also, fertilizing and foliar spraying of trees in some forest areas should be considered.
Soil science
Ali Sarabchi; Hossein Rezaei; farzin 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
mohamad malehmir chegini; AHMAD GOLCHIN
Abstract
Introduction:
Soil contamination with heavy metals poses a significant threat to both environmental and human health. Anthropogenic activities, including the use of chemical fertilizers and pesticides, industrial processes, wastewater disposal, and mining, contribute to the accumulation of heavy metals ...
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Introduction:
Soil contamination with heavy metals poses a significant threat to both environmental and human health. Anthropogenic activities, including the use of chemical fertilizers and pesticides, industrial processes, wastewater disposal, and mining, contribute to the accumulation of heavy metals in soil. These contaminants can then be taken up by plants 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, biochars, and activated carbons were added to a soil contaminated with lead, zinc, and cadmium at four application rates (0, 2.5, 5, and 10% by weight) in triplicate, 4.5 kg pots. 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 to the control.
Results:
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 highest dry weight of corn shoots and roots was observed in treatments containing activated carbon produced at 500 °C and applied at a rate of 5%. Conversely, 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.
Heavy metals are persistent soil pollutants that pose significant risks to environmental and human health. The application of soil amendments such as biochar and activated carbon has been proposed as an effective strategy for reducing the mobility of heavy metals in soil. This study examines the impact of various organic wastes (wheat straw, walnut shells, and almond shells), along with the biochar and activated carbon derived from these wastes, on immobilizing heavy metals (lead, zinc, and cadmium) and promoting corn plant growth in contaminated soil under greenhouse conditions. Biochars were produced at two pyrolysis temperatures, 300°C and 500°C, and subsequently activated with phosphoric acid and the experimental treatments were added to a contaminated soil at four levels (0, 2.5, 5 and 10% by weight) and in three replicates The results showed that organic wastes, biochars, and activated carbons significantly reduced the concentration of available heavy metals in the soil at a probability level of 5%. Activated carbons had the most effect and organic waste had the least effect. 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 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 dry weight, respectively, and in the roots, they were 206, 1095 and 20 mg/kg 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 findings of this study suggest that activated carbon is an effective and sustainable method for remediating soils contaminated with heavy metals and enhancing plant growth.
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
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.
Soil science
A. Hassanzadeh; M. Hamidpour
Abstract
IntroductionLayered double hydroxides (LDH) have gained considerable attention for their potential application in agriculture, serving as a slow release sources of essential nutrients for plants. The appraising of LDH as a favorable fertilizer is in the early development, and more studies on the nutrient ...
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IntroductionLayered double hydroxides (LDH) have gained considerable attention for their potential application in agriculture, serving as a slow release sources of essential nutrients for plants. The appraising of LDH as a favorable fertilizer is in the early development, and more studies on the nutrient release mechanism of LDH are needed to answer the question of how LDH could replace commercial fertilizers for providing the stable nutrients for plants. Although several studies on the release of P from LDH exist in the literature, no information regarding ratios of divalent cation (M2+) to trivalent cation (M3+) in LDHs on phosphate release from LDHs is available. So, it is important to raise our knowledge about various parameters like pH and time on the solubility of LDHs. This study aimed to investigate the effects of pH and the ratios of M2+/M3+on the kinetics release of P from Mg-Al-LDH. Materials and MethodsAll the chemicals in this research, such as magnesium nitrate hexahydrate (Mg (NO3)2.6H2O) and aluminum nitrate nonahydrate Al(NO3)3.9H2O were of analytical grade and obtained from Merk (USA). The solutions were made with decarbonated pure water without impurities (electrical resistivity = 18 MΩcm). Two nitrate forms of Mg-Al-LDH were synthesized using the co-precipitation method at constant pH by varying the Mg/Al ratios (2:1 and 3:1) in the precursor solution. Briefly, 50 mL of 1M solution containing nitrate salt of divalent cations (Mg(NO3)2.6H2O) and trivalent cations (Al(NO3)3.9H2O) in the appropriate ratios (2:1 and 3:1) were added simultaneously for 2h to 400 mL of 0.01M solution of sodium hydroxide while being stirred vigorously in a nitrogen atmosphere. The pH was kept at 9.5 by adding volumes of 3 M NaOH. Afterward, the material was ripened in the synthesis mixture for 2 h and centrifuged at 3000 rpm for 20 min. The precipitates were washed by three washing-centrifugation cycles with Milli-Q water and subsequently dried at 70 °C. In this study, LDH-P was made by ion exchange. The LDH-N were treated with 0.05 M KH2PO4 solutions at pH 7.2. The suspensions were shaken end-over-end for 24h, followed by centrifugation, washing, and drying as described above. After digesting the dried LDHs in aqua regia (3:1 HCl/HNO3), the total P concentration of the LDHs was determined. The chemical composition of the synthesized LDHs was determined by graphite furnace atomic absorption spectrophotometry (SavantAA, GBC) after acid digestion (3:1 HCl/HNO3). Crystallization and morphology of the LDHs were characterized via scanning electron microscopy (SEM) and X-ray diffraction (XRD). The XRD patterns were prepared using an x-ray diffractometer (Panalytical x Pert Pro, Netherlands), at scan step time of 1s from 2θ=5° to 2θ=70° (40KV and 30 mA), and with a step size of 0.0260, which were used to identify the mineral phases. The phase purity was surveyed by comparing these XRD diagrams with those found in the literature. The SEM photographs were gained on a scanning electron microscope (Sigma VP, Germany). Fourier Transform Infrared (FTIR) spectrum was done on a Nicolet iS10 FT-IR spectrometer by utilizing KBr pressed disk technique.A batch study was done to determine the effect of different ratios of M2+/M3+ in LDHs at different pH 6.0 and 8.0 on the release of P from LDHs. Briefly, 0.01 g of synthesized LDH were put in a centrifuge tube mixed with 10 ml of 0.03M KNO3 at initial pH=6 and 8. Suspensions were shaken at a constant temperature (25±0.5 °C) and agitation (180 rpm) by using an incubator shaker for 8h. Phosphorus concentration in supernatant solutions was measured by vanadate yellow method at 470 nm wavelength.In order to investigate the kinetics of phosphorus release, LDH-P1 (2:1) and LDH-P2 (3:1) were used at two initial pHs of 6 and 8. First, 0.012 g of LDH sample was placed in 120 ml of KNO3 electrolyte solution (with ionic strength of 0.03 M) in an Erlenmeyer flask. The flasks were shaken for 5 to 1175 min by an incubator shaker at 100 rpm. Then the suspensions were centrifuged at a speed of 4000 rpm for 20 minutes and the phosphorus concentration was determined by the method described previously. All experiments were performed with three repetitions. Two equations (pseudo-second-order and parabolic diffusion) were used to fit the kinetics data. Results and DiscussionAccording to the XRD patterns, the sharpness and reflection of diffraction planes (003) and (006) pertained to layer structures. The basal spacing as calculated by Bragg’s law (nλ = 2d sin θ) were 7.94 and 8.0 Å for Mg-Al-NO3 with M+2/M+3 2:1, 3:1 respectively. The XRD patterns of the LDHs exhibited a distinct characteristic reflection (003), which indicated that the basal spacing decreased as the Mg/Al ratio decreased (higher AEC). In addition, the decreased basal spacing is linked with a decrease in the interlayer spacing. The different basal spacing of LDH were related to the layer charge density, the content of water, and the reorientation of anions in the interlayer of LDH. The intercalation of phosphate anions into Mg/Al LDH is in adaptation with the change toward lower 2θ angles of the (001) reflections corresponding to the expansion of the basal distance d003 compared to the host Mg/Al-NO3-.Two bands of FT-IR spectrums around 3470 and 1655 cm-1 for all synthesized LDH materials designate stretching vibrations of the O-H group of hydroxide layers and the interlayer water molecules. The band vibration of phosphate was perceived at 1051 cm−1 and 1064 cm-1, reflecting the formation of inner-sphere surface complex (M-O-P) between dihydrogen phosphate ions and MgAl-LDH materials. It indicated that the phosphate exchange process may be resulted in the formation of bidentate and monodentate surface complexes. According to the SEM images, the well-crystallized and plate-like morphology were typical for layer double hydroxides. The results of the X-ray energy dispersive spectroscopy (EDS) analysis showed, the only elements that existed in the LDH-N were Mg, Al, N, and O, whereas Mg, Al, P, and O were detected in the LDH-P. The results showed that increasing the pH from 6 to 8 in the presence of 0.03 M potassium nitrate background electrolyte led to an increase in phosphorus released from both types of LDH. For example, by increasing the initial pH of suspensions from 6 to 8, the amount of cumulative phosphorus released from LDH-P1 increased from 38.59 mg kg-1 to 41.91 mg kg-1 at equilibrium. In all studied pHs, phosphorus release from LDH-P1 in background electrolyte was lower than LDH-P2. For example, at pH 6 and 8, the amount of cumulative phosphorus released from LDH-P2 was 1.46 and 1.33 times higher than LDH-P1 at equilibrium, respectively. The cumulative phosphorus release kinetics from the studied LDHs showed that the amount of phosphorus release accelerated with increasing time. Phosphorus release from LDH continued at a higher rate from 0 to 400 minutes in the first stage and at a slower rate during 400-1175 minutes. Also, based on the results, among the studied kinetic equations, pseudo-second-order and parabolic diffusion equations had the best fit on phosphorus release data. ConclusionThe results of this research showed that the release of phosphorus from LDH is dependent on time, pH and the type of LDH. Based on the results of fitting the kinetics models to the experimental data, the release rate of phosphorus from LDH-P2 (3:1) was higher than that of LDH-P1 (2:1). Cumulative phosphorus release from LDH-P2 compared to LDH-P1 was 46.54, 33.61% higher at pH 6 and 8, respectively.
Soil science
Z. Sohrabzadeh; Y. Kooch
Abstract
Introduction Shrub covers play a pivotal role in pasture ecosystems, exerting considerable influence on various biochemical processes that occur within the habitat and surface layers of the soil. Despite their significance, there is a scarcity of research exploring the impact of different ...
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Introduction Shrub covers play a pivotal role in pasture ecosystems, exerting considerable influence on various biochemical processes that occur within the habitat and surface layers of the soil. Despite their significance, there is a scarcity of research exploring the impact of different types of shrubs covers on soil properties within pasture ecosystems. Consequently, this present study was undertaken to address this gap in knowledge and investigate the effects of shrub cover on soil characteristics specifically within a semi-arid climate, which is known for its delicate and vulnerable habitats. Materials and MethodsThe implementation of this research involved the consideration of the mountainous region of Kiakola, Nowshahr city. The current investigation focused on assessing the impact of various shrubs, namely Carpinus orientalis Miller, Crataegus microphylla C. Koch, Berberis integerrima Bunge, Prunus spinosa L., and Rhamnus pallasii Fisch. and C. A. Mey, on specific soil properies within the mountainous area of Kiakla, Nowshahr city. To carry out this research, 15 sites were selected for each of the aforementioned shrub species. Soil samples were collected from under the canopy of these species, specifically at a depth of 0-10 cm and a surface area of 30 cm × 30 cm. A total of 75 soil samples were then taken to the laboratory for analysis. The samples were divided into two parts: one part underwent physical and chemical tests after air-drying and passing through a 2 mm sieve, while the other part was stored at 4 degrees Celsius for biological tests. The presence or absence of significant differences in soil properties related to the type of shrub cover under investigation was determined using a one-way analysis of variance test. Principal component analysis (PCA) was utilized to establish the relationship between different soil characteristics within the studied shrub covers. Results and DiscussionAccording to the findings of this investigation, alterations in the shrub species present in the examined pasture habitat resulted in modifications to the majority of soil quality properties. Nevertheless, no statistically significant disparity was observed in the quantity of soil organic matter. However, it is worth noting that the quantity of organic matter in the subsoil of Carpinus species exceeded that of the other examined shrubs. Carpinus and Crataegus shrubs were associated with the lowest values of bulk density, while the shrubs under investigation had no significant impact on soil particle density. Furthermore, the subsoil of the Carpinus shrub cover exhibited the highest values of soil porosity. In the studied area, the most stable soil aggregates were observed beneath the Carpinus and Rhamnus shrubs. The subsoil of Rhamnus and Carpinus shrubs exhibited the highest and lowest quantities of sand, respectively. Similarly, the subsoil of Carpinus and Rhamnus displayed the highest and lowest quantities of clay, respectively. The soil under Rhamnus displayed the highest ratio of CR and MCR indices, whereas the subsoil of Carpinus exhibited the lowest values of these indices. Fulvic and humic acids demonstrated the greatest values beneath the Carpinus, Crataegus, Berberis, Prunus, and Rhamnus shrubs, respectively, following a comparable pattern. Additionally, the subsoil of Carpinus exhibited the greatest quantity of microbial ratio, while the soil under Rhamnus displayed the lowest quantity of this characteristic. The outcomes of the principal component analysis (PCA) revealed that the quantity of organic matter, clay content, fulvic and humic acids, porosity, and stability of soil aggregate in the soil beneath Carpinus played a significant role in enhancing the soil microbial ratio of this shrub in comparison to the other shrubs. Conclusion The findings of this investigation validate the capability of Carpinus foliage to ensure the conservation of soil quality indicators on the hilly grasslands of northern Iran. Therefore, it is proposed that restoration efforts be conducted in the designated region and other areas with similar ecological conditions. Additionally, it is recommended that special attention be given to the implementation of Carpinus and other indigenous shrub species to protect soil integrity.
Soil science
S. Naseri; Sh. Kiani; H.R. Motaghian
Abstract
IntroductionUrea is one of the nitrogen chemical fertilizers for vegetable production in soil. But it is seldom used in soilless cultures. Leafy vegetables such as Lettuce (Lactuca sativa L.) contain high levels of nitrate and attempts have been made to reduce the nitrate concentration in this crop for ...
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IntroductionUrea is one of the nitrogen chemical fertilizers for vegetable production in soil. But it is seldom used in soilless cultures. Leafy vegetables such as Lettuce (Lactuca sativa L.) contain high levels of nitrate and attempts have been made to reduce the nitrate concentration in this crop for human consumption. Using reduced forms of nitrogen, i.e. urea, is one of the applied strategies for reducing nitrate accumulation in lettuce. Little information is available concerning urea as a source of nitrogen for production of leafy vegetables such as lettuce in soilless culture. This experiment was conducted to investigate the effect of different ratios of urea:nitrate in nutrient solution on the growth indices, yield and nitrate accumulation of red French lettuce (Lactuca sativa L. cv. Lolla Rossa) in soilless culture. Materials and MethodsA hydroponic experiment using completely randomized design was carried out with seven ratios of urea:nitrate in nutrient solution and four replications in the research greenhouse of Shahrekord University. Urea:nitrate ratios in nutrient solution were: 0:100, 10:90, 20:80, 30:70, 40:60, 50:50 and 60:40. Lettuce seedlings were grown in 2 L plastic pots (one plant per pot) containing mixture of cocopeat + perlite at the ratio of 2:1 (v/v) and were manually fertigated with nutrient solutions on a daily basis. Four weeks after transplanting, lettuce plants were harvested and fresh weights of shoot and root were determined. Plant growth indices including of plant height, plant diameter, leaf length, leaf width, leaf number, leaf greenness index and leaf brix level were measured. After measuring the growth indices, the leaves were grouped separately according to leaf numbers 1-10=outer leaves, >11= inner leaves. The samples were dried in an oven at 60 °C and were ground. Nitrate concentrations in samples were determined calorimetrically using a spectrophotometer at a wavelength of 410 nm. Analysis of variance was performed using SAS software version 9.4. Means comparison was conducted using least significant difference test at 0.05 probability level. Results and DiscussionThe results indicated that application of different ratios of urea to nitrate in nutrient solution had not significant effect on the lettuce growth indices including of plant diameter, leaf length, leaf width, leaf number, leaf greenness index and leaf brix level in comparison with 0:100 of urea:nitrate ratio. Also, root and shoot fresh weights were not affected by urea:nitrate ratio in nutrient solution. The greatest quantity of shoot fresh weight (141 g per plant) was obtained with a 50:50 urea:nitrate ratio. However, this was not significantly different from the shoot fresh weight (125 g per plant) observed when urea was not included in the nutrient solution. Shoot nitrogen concentration (except for plants nourished with a 50:50 urea:nitrate ratio) was not affected by increasing the urea:nitrate ratio in the nutrient solution. The results revealed that application of urea in nutrient solution effectively provided the nitrogen requirement of lettuce. This indicates that lettuce plants can efficiently hydrolyze urea and use it efficiently as a nitrogen source. Application of urea in the nutrient solution led to significant decrease in the nitrate concentration of lettuce root (P< 0.05). Moreover, increasing urea:nitrate ratio in nutrient solution resulted in significant decrease of the nitrate concentration of outer leaves, inner leaves and all leaves of lettuce (P< 0.01). The highest and lowest nitrate concentration in inner, outer and all leaves of lettuce were obtained in plants nourished with 0:100 and 50:50 urea:nitrate ratio in nutrient solution, respectively. Application of urea:nitrate ratio of 50:50 led to the meaningful decrease of nitrate concentration in root (43%), outer leaves (41%), inner leaves (44%) and all leaves (43%) of lettuce in comparison with 0:100 of urea:nitrate ratio. Urea had a repressive effect on nitrate influx and decreased its uptake by plants. Also, after urea uptake by plant root, it is first degraded by cytosolic ureases and then ammonium is incorporated via the GS-GOGAT (Glutamine Synthetase- Glutamine α-OxoGlutarate Amino Transferaze) cycle. Therefore, application of urea in nutrient solution can lead to the reduction of nitrate accumulation in plants. ConclusionBased on the shoot fresh weight and nitrate concentration in lettuce leaves, replacing 50% of nitrate in nutrient solution with urea is recommended for red French lettuce production in hydroponic culture under the conditions of the present study. Compared to other nitrogen fertilizers, urea has a lower price and its application in nutrient solution is useful in reducing production costs.
Soil science
A. Barikloo; P. Alamdari; A. Golchin
Abstract
IntroductionHeavy metals such as lead, aluminum, mercury, copper, cadmium, nickel, and arsenic are now commonly found worldwide. Among these, cadmium and lead are the most hazardous, posing significant risks to both the environment and human health. Cleaning soils contaminated with organic and inorganic ...
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IntroductionHeavy metals such as lead, aluminum, mercury, copper, cadmium, nickel, and arsenic are now commonly found worldwide. Among these, cadmium and lead are the most hazardous, posing significant risks to both the environment and human health. Cleaning soils contaminated with organic and inorganic contaminants is one of the most significant and fundamental challenges facing society today. One effective method for soil purification is to extract or immobilize the contaminant within the soil. Materials and MethodsIt is unclear how water-soluble polymers contribute to the immobilization of heavy metals. The purpose of this study is to examine how various polymers affect the immobilization of lead, zinc, and cadmium in the soil near a lead and zinc mine in the province of Zanjan. A factorial experiment with three replications was conducted using a randomized complete block design. The experimental treatments included one type of soil and three different kinds of acrylic polymers (cationic, nonionic, and anionic) applied at four different levels (0, 0.05, 0.1, and 0.2). The absorbable amounts of lead, zinc, and cadmium were tested at various intervals after the polymers were applied to the soil samples. After that, SAS statistical software was used to examine the data. To do this, the Duncan multiple range test was used to compare the means. The necessary tables and graphs were then created using Excel. Results and DiscussionThe findings demonstrated that, at 1% probability level, the kind of polymer had a considerable impact on the amount of lead, zinc, and cadmium that may be absorbed in the soil. The average concentration of soil-absorbable lead for the different types of polymers employed was 239.8, 260.15, and 267.65 mg/kg; anionic polymer had the lowest concentration. Stated differently, anionic polymer decreases the capacity to absorb lead and stabilizes more lead in the soil than the other two forms of polymer. Anionic polymers most likely have a stronger impact on soil granulation. Additionally, at 1% probability level, the impact of acrylic polymer intake on the amount of lead, zinc, and cadmium absorbable in the soil was considerable. With an increase in the amount of polymer utilized in the soil, the greatest absorbable lead concentration (301.58 mg/kg) in the control treatment dropped to the lowest absorbable lead concentration (0.2). It was possible to determine the polymer percentage and the lead concentration, which came out to be 205.9 mg/kg of soil. Zinc concentration dropped as acrylic polymer consumption increased; in the control treatment, absorbable zinc concentrations ranged from 0.2 to 83.5 mg/kg of soil, with 0.2 being the highest concentration. At 1% probability level, the impact of the polymer's contact time with the soil on the amount of lead, zinc, and cadmium that the soil may absorb was significant. As a result, the tested soil had 414.52 mg of these elements at the initial stage of polymer treatment. The quantity of absorbable lead in the soil became 66% immobilized after a month, and after 720 hours, the amount of absorbable lead dropped to 141.83 mg/kg. As the polymer's contact time with the soil increased, so did the concentration of absorbable zinc in the soil. At 1% probability level, there was a strong correlation between the kind and amount of acrylic polymers and the amount of lead, zinc, and cadmium that may be absorbed in the soil. The ingestion of 0.2% anionic polymer resulted in the largest amount of lead immobilization, lowering the soil's absorbable lead concentration from 300 to 192 mg/kg of soil. A higher amount of anionic polymer immobilized the lead, and both cationic and non-ionic polymers were positioned after it. Additionally, anionic polymer was more prevalent than cationic polymer. It caused the non-ionic polymer's absorbable zinc to become immobile. Following 720 hours of polymer treatment, the soil's absorbable zinc element was immobilized to a greater extent by the anionic polymer (20%) than by the cationic and non-ionic polymers (26%), respectively. In comparison to the original concentration, the largest amount of immobilization by anionic polymer after one month was 78%, and the lowest amount of immobilization by nonionic polymer was 61%. Anionic polymer was 27% more effective than non-ionic polymer, 18% more effective than cationic polymer, and stabilized more cadmium. Conclusion The results of this study showed that with increasing the duration of contact of polymers used with the soil, the amount of mobility of heavy metals in the soil decreased and also with increasing the amount of polymer consumption, the rate of metal stabilization in the soil increased. Anionic polymers immobilize more lead, zinc and cadmium in soil. To reduce the mobility of lead, zinc and cadmium and improve the stability and increase aggregation in soil, the use of acrylic polymer in contaminated soil is recommended.
Soil science
Sh. Asghari; M. Hasanpour Kashani; H. Shahab Arkhazloo
Abstract
IntroductionThe penetration resistance (PR) of the soil shows the mechanical resistance of the soil against the penetration of a conical or flat probe; it is important in terms of seed germination, root growth and tillage operations. In general, if the PR value of a soil exceeds 2.5 MPa, the growth and ...
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IntroductionThe penetration resistance (PR) of the soil shows the mechanical resistance of the soil against the penetration of a conical or flat probe; it is important in terms of seed germination, root growth and tillage operations. In general, if the PR value of a soil exceeds 2.5 MPa, the growth and expansion of roots in the soil will be significantly limited. The direct measurement of PR is also a laborious and costly task due to instrumental errors. Therefore, it is useful the use of different models such as multiple linear regression (MLR), artificial neural network (ANN) and gene expression programming (GEP) to estimate PR through easily accessible and low-cost soil characteristics. The objectives of this research were: (1) to obtain MLR, ANN and GEP models for estimating PR from the easily accessible soil variables in forest, range and cultivated lands of Fandoghloo region of Ardabil province, (2) to compare the accuracy of the aforementioned models in estimating soil PR using the coefficient of determination (R2), root mean square error (RMSE), mean error (ME) and Nash-Sutcliffe coefficient (NS) criteria. Materials and MethodsDisturbed and undisturbed samples (n = 80) were nearly systematically taken from 0-10 cm soil depth with nearly 50 m distance in forest (n = 20), range (n = 23) and cultivated (n = 37) lands of Fandoghloo region of Ardabil province, Iran (lat. 38° 24' 10" to 38° 24' 25" N, long. 48° 32' 45" to 48° 33' 5" E) in summer 2023. The contents of sand, silt, clay, CaCO3, pH, EC, bulk (BD) and particle density (PD), organic carbon (OC), gravimetric field water content (FWC), mean weight diameter (MWD) and geometric mean diameter (GMD) were measured in the laboratory. Relative bulk density (BDrel) was calculated using BD and clay data. Mean geometric diameter (dg) and geometric standard deviation (σg) of soil particles were computed by sand, silt and clay percentages. The penetration resistance (PR) of the soil was measured in situ using cone penetrometer (analog model) at 5 replicates. Data randomly were divided in two series as 60 data for training and 20 data for testing of models. The SPSS 22 software with stepwise method, MATLAB and Gene Xpro Tools 4.0 software were used to derive multiple linear regression (MLR), artificial neural network (ANN) and gene expression programming (GEP) models, respectively. A feed forward three-layer (2, 5 and 6 neurons in hidden layer) perceptron network and the tangent sigmoid transfer function were used for the ANN modeling. 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, as they are 30, 3, 8, and +, respectively. The rates of genetic operators were chosen according to literature studies. The accuracy of MLR, ANN and GEP models in estimating PR were 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 clay loam (n = 11), sandy clay loam (n = 6), sandy loam (n = 12), loam (n = 13), silty clay loam (n = 14), silty clay (n = 1) and silt loam (n = 23) textural classes. The values of sand (13.14 to 64.79 %), silt (21.11 to 74.96 %), clay (2.95 to 42.18 %), OC (1.01 to 7.17 %), FWC (11.58 to 50.47 mass percent), BD (0.84 to 1.43 g cm-3) and PR (1.03 to 5.83 MPa) showed good variations in the soils of the studied region. There were found significant correlations between PR with FWC (r = - 0.45**), silt (r = - 0.36**) and σg (r = 0.36**). Due to the multicollinearity of silt with σg (r = -0.84**), the σg was not used as an input variable to estimate PR. Generally, 3 MLR, ANN and GEP models were constructed to estimate PR from measured readily available soil variables. The results of MLR, ANN and GEP models showed that the most suitable variables to estimate PR were FWC, silt and BDrel. The values of R2, RMSE, ME and NS criteria were obtained equal 0.44, 1.19 MPa, 0.19 MPa and 0.36, and 0.92, 0.41 MPa, -0.05 MPa and 0.92, 0.79, 0.91 MPa, 0.13 MPa, 0.63 for the best MLR, ANN and GEP models, respectively. The former researchers also reported that there is a negative and significant correlation between PR with FWC. Conclusion The results indicated that field water content (FWC), silt and relative bulk density (BDrel) were the most important and readily available soil variables to estimate penetration resistance (PR) in the studied area. According to the lowest values of RMSE and the highest values of NS, the accuracy of ANN models to predict soil PR was higher than MLR and GEP models in this research.
Soil science
N. Mollaei; M. Sheklabadi; M. Nael
Abstract
IntroductionSoil aggregate stability is a crucial indicator for evaluating soil structure, quality, and health. This index affects the physical and hydrological functions of the soil, which, in turn, depend on plant primary production and the capacity of organic carbon decomposition. Soil organic carbon ...
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IntroductionSoil aggregate stability is a crucial indicator for evaluating soil structure, quality, and health. This index affects the physical and hydrological functions of the soil, which, in turn, depend on plant primary production and the capacity of organic carbon decomposition. Soil organic carbon plays a positive role in the formation and stability of soil aggregates. Soil organic carbon (SOC) causes a rapid decrease in water penetration into soil aggregates by creating a water-repellent coating around them and increases their stability against instant wetting stress. Land use and management, including cultivation systems and tillage methods, have an important impact on the stability and size distribution of soil aggregates. Mechanized sugarcane cultivation has a long history in Khuzestan province, particularly in Haft Tepe sugarcane cultivation and industry. Haft Tepe Agriculture is the first sugar production unit in Iran. Despite the increase in the use of chemical fertilizers, the yield of sugarcane crops has been decreasing due to the destruction of the physical properties of the soil. The study aimed to investigate the effects of different sugarcane cultivation systems on soil physicochemical-biological properties and soil stability indices in parts of Khuzestan province. Materials and MethodsSoils were sampled from the surface of five farms in the Haft Tepe sugarcane cultivation complex located in the northwest of Khuzestan province. The farms included single-row, new planting cultivation (S-P); single-row, third ratoon cultivation (S-R3); double rows, new planting cultivation (D-P); double rows, first ratoon cultivation (D-R1); and uncultivated land (barren) that had been left unused for a long time. Soil organic carbon content, active carbon content, basal respiration, induced respiration, water-stable aggregates, and aggregate organic carbon fractions were measured in the sampled soil. Mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates were also calculated. Results and DiscussionThe study found that the organic C content was highest in the double-rows+new planting (D-P) method and lowest in uncultivated land (0.95% and 0.12%, respectively). The increase in plant density, biomass, and plant residue addition in D-P cultivation has led to an improvement in SOC content. The higher SOC content in cultivated lands compared to uncultivated land indicates the positive effect of many years of cultivation and irrigation. Among the different cultivations, double-row new planting (D-P) cultivation had significantly higher active carbon. In D-R1 cultivation, returning plant residues to the soil increased the SOC (0.59%) and active carbon content. The burning of sugarcane plant residues during harvesting and land preparation for new sugarcane cultivation in S-P fields appears to have led to a decrease in active carbon. Basal respiration and induced respiration values were significantly higher in single-row, third ratoon (S-R3) and double-row, new planting (D-P) cultivations, respectively. In S-R3 cultivation, the older plants and increased root biomass provided more rhizospheric organic C for microorganisms, resulting in higher microbial activity and respiration. Microorganisms transform and decompose soil organic matter, which is a source of energy for their metabolic processes. Therefore, there is a close relationship between organic matter and soil microorganisms. Lower basal respiration in newly planted lands may be due to the process of land preparation for cultivation. Additionally, single-row new-planted farms had a clayey texture, which could reduce soil respiration. In general, the recycling of organic matter and microbial activity is lower in fine-textured soils compared to coarse-textured soils. The highest MWD and GMD were found in single-row, third ratoon (S-R3) and single-row, new planting (D-P) cultivations. The uncultivated land had the lowest MWD and GMD, indicating unstable soil structure due to low SOC content. The lower MWD observed in S-P cultivation could be related to tillage and hilling up operations. S-R3 cultivation had more plant residues compared to other cultures. Higher plant ages and increased root biomass and rhizodeposits led to an increase in soil aggregate formation and stability. Soil tillage, which reduces soil organic carbon, can decrease the stability of soil aggregates and structure. The S-P and D-P cultivations had the highest value of coarse aggregates (larger than 2 mm) and fine aggregates (0.53-2 mm). The highest amount of medium aggregates were observed in S-P, D-P, and D-R1 cultivations. Agricultural operations can break large soil aggregates into smaller ones, while low SOC content and burning of sugarcane residues can reduce the formation of large aggregates. The study found statistically significant differences in the OC content of aggregates among the different cultivations. The highest content of aggregates OC was found in coarse aggregates (0.25-2.0 mm) of D-R1, D-P, and S-P cultivations. ConclusionThis study investigates the impact of mechanized and long-term sugarcane cultivation on the physical and biological properties of soil. Overall, the water stable aggregates and MWD were found to be unsuitable in some of the studied fields due to the low amount of SOC. This is primarily caused by the annual burning of sugarcane residue. Therefore, returning plant residues after harvesting is suggested as a significant solution to improve problems related to compaction, soil instability, and their harmful consequences.
Soil science
Kh. Salarinik; M. Nael; M. Sayyari; S.S. Moosavi
Abstract
IntroductionApplication of agricultural waste composts, in addition to improving soil fertility, has positive effects on the quality of agricultural products and the environment by reducing the use of chemical fertilizers and recycling agricultural waste. Spinach (Spinacea oleracea L.) is a suitable ...
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IntroductionApplication of agricultural waste composts, in addition to improving soil fertility, has positive effects on the quality of agricultural products and the environment by reducing the use of chemical fertilizers and recycling agricultural waste. Spinach (Spinacea oleracea L.) is a suitable plant for studying the effects of composts and chemical fertilizers due to some physiological characteristics such as high antioxidant activity and oxalic acid, significant amount of mineral compounds and vitamin C, and nitrate accumulation. Despite relatively extensive studies on the effect of different composts on plants, no study has been conducted so far to investigate the effect of grape pomace (GP) composts on plants in Iran. Therefore, the objectives of the present study were: 1- to investigate the effect of different GP composts on yield, nutrient elements, and some physiological parameters of spinach in comparison with two levels of urea fertilization in a pot experiment in two consecutive growing seasons, and 2- to investigate the relationship between nutrient elements and physiological indicators of spinach based on principal component analysis. Materials and MethodsTo investigate the effects of GP composts on yield, nutrient elements, and physiological parameters of spinach (Persius hybrid), an outdoor pot experiment was conducted in a randomized complete block design with eight compost treatments, two levels of urea fertilizer (46%), and a control treatment (C0) in three replications and two consecutive growing seasons (spring and fall). Compost treatments included: High grape pomace (HG) (60-63%) with chickpea straw and alfalfa (HG-Ch-A), high GP with chickpea straw and sugar beet pulp (HG-Ch-B), high GP with alfalfa and sugar beet pulp (HG-A-B), high GP combined with chickpea straw, alfalfa, and sugar beet pulp (HG-All); four other compost treatments included low level of grape pomace (LG) (37-42%) combined with other residues/wastes similar to the first four treatments (LG-Ch-A, LG-Ch-B, LG-A-B, and LG-All). Urea fertilizer treatments included: 150 kg per hectare (C150) (two-stage top dressing) and 500 kg per hectare (C500) (three-stage top dressing). Prior to planting, the composts were separately mixed into the soil (sandy loam) at a rate of 2% by weight(. The first crop was grown for 50 days in May 2018 and the second crop was grown for 45 days in September 2018. In both seasons, plant samples were taken in the early morning at the end of the growing season to determine the fresh and oven-dried weight of shoot and root samples, leaf area, nutrient elements, and some physiological indicators. Some of the shoot samples were wrapped in aluminum foil and stored in a freezer (-20 °C) to determine the amount of chlorophyll (type a, type b, and total), carotenoids, total phenol, vitamin C, and antioxidant activity. Oxalic acid, zinc, iron, copper, sodium, potassium, phosphorus, calcium, magnesium, and nitrate were determined in oven-dried samples. One-way ANOVA was applied separately to spring and fall data, and mean comparisons were made using Duncan's test at the 0.05% level. Principal component analysis was used to determine the relationships between nutrient elements and physiological indicators of spinach. Results and DiscussionThe LG-Ch-A and C500 treatments (in spring cultivation), and the LG-A-B, LG-All, and HG-All treatments (in fall cultivation) had the highest leaf number, leaf area, and yield and were significantly difference from the C0 treatment. The high yield in C500, LG-Ch-A, LG-All, and HG-All treatments was associated with nitrate accumulation in spinach. In both cultivations, there was a significant positive correlation between the amount of P, K, Mg and Zn in spinach and the amount of these elements in the corresponding composts. A synergistic relationship was also observed between P and Mg; P and Zn; and Mg and Zn in spinach. On the other hand, an antagonistic relationship was observed between Ca and Mg in spinach because a high concentration of calcium inhibits magnesium uptake by reducing cell permeability. In both seasons, the chemical fertilizer treatments showed the highest amount of chlorophyll and carotenoids because these compounds increase with increasing nitrogen availability. On the contrary, the amount of antioxidant activity was significantly higher in compost treatments than in chemical treatments. In the spring cultivation, the highest and lowest amount of oxalic acid and oxalic acid/Ca ratio were observed in the LG-Ch-B and HG-All treatments, respectively. Interactions between nutrients and physiological indicators were observed. The uptake of all micronutrients, P, and Mg (in both cultivations) and K (in the fall cultivation) was inhibited by high Ca concentration. With the decrease of micronutrients uptake, an increase in nitrate accumulation may occur because micronutrients are present in the structure of nitrate reducing enzymes. The interdependence between Mg and oxalic acid/Ca (in spring), K and oxalic acid (in fall), and Na and oxalic acid/Ca (in fall) may be related to the role of oxalates in the uptake of mineral ions by plants, since oxalates are usually combined with Na, Mg, Ca, and K in the form of soluble and insoluble salts. ConclusionThe use of urea chemical fertilizer (at two levels) and agricultural waste composts had different effects on the physiological indicators, growth and nutrients in spinach. Spinach grown in soils treated with composts rich in P, K, Mg, and Zn had higher nutritional value. The grouping of treatments by principal component analysis showed that chemical and control treatments were clearly separated from compost treatments with high amount of chlorophyll, carotenoid, nitrate, K, and Zn and low amount of oxalic acid, oxalic acid/Ca ratio, antioxidant activity, phenol, and Na. In general, the use of C500, LG-Ch-A, LG-All and HG-All treatments is not recommended due to nitrate accumulation in spinach.
Soil science
O. Toorajzadeh; H. Piri; A. Naserin; M.M. Chari
Abstract
IntroductionAppropriate and practical use of agricultural waste reduce the pressure on the environment. Recently, there has been significant promotion of biochar utilization in agricultural lands. It serves as a valuable source of organic material for enhancing plant growth and as an effective soil amendment ...
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IntroductionAppropriate and practical use of agricultural waste reduce the pressure on the environment. Recently, there has been significant promotion of biochar utilization in agricultural lands. It serves as a valuable source of organic material for enhancing plant growth and as an effective soil amendment to improve soil properties. Due to its unique chemical and physical properties, biochar can be used as a soil conditioner and has many benefits for optimal agricultural and environmental management. Studies have shown that biochar is a useful amendment for improving the physical and chemical properties of soil and effective in maintaining organic matter and soil moisture. Materials and Methods This research was conducted with the aim of investigating the effects of biochar on the physical and chemical properties of soil under conditions of water stress and irrigation using saline water. The experiment was carried out in a factorial based on a completely randomized design with three replications in greenhouse conditions. The treatments include three irrigation water treatments (60, 80, and 100 percent water requirement of the plant, respectively, I1, I2, and I3), three treatments of biochar prepared from northern forest trees at a temperature of 300 degrees Celsius (0, 2, and 4 percent by weight of potting soil, respectively, B1, B2, and B3) and three water quality treatments (with electrical conductivity 1, 4 and 7 dS/m, respectively, S1, S2 and S3). The pots were weighed every other day and at each level of biochar and salinity, the water deficit up to the agricultural moisture level was calculated based on the changes in the pot's weight. After harvesting (in the first half of April 2022), in order to investigate the effect of biochar on the amount of soil nutrients and some physical and chemical parameters of the soil under the conditions of water stress and irrigation water salinity, sampling was done from the soil of each pot. The samples were taken to the laboratory and parameters of apparent and actual specific gravity, acidity and salinity of the soil, percentage of nitrogen, phosphorus and potassium absorbable of the soil were measured in the laboratory. Referring to the yield to irrigation water ratio, water productivity is obtained by the following relation (Payero et al., 2009): WP=Y/IR, where, WP represents water productivity (kg/m3), Y denotes the yield (kg/ha), and IR shows the amount of irrigation water (m3/ha). Analysis of variance for the results obtained from different treatments was conducted using SAS software (SAS 9.1, SAS Institute, Cary, NC, USA). The mean values of the main factors and interactive effects were compared using the Duncan method at the 1% and 5% levels of significance. Results and DiscussionThe results showed that the amount of biochar, irrigation water and water salinity and their mutual effects had a significant effect on the measured parameters at the probability level of one and five percent. Adding 2 and 4 mass percent biochar to the soil increased the amount of phosphorus (35 and 60%, respectively), potassium (57% and 61%), nitrogen (83% and 91%), pH (13% and 13%) and electrical conductivity (EC) (13% and 57%) of the soil. By adding 2% and 4% of biochar to the soil, the actual specific gravity of the soil decreased by 13% and 21%, respectively, and the apparent specific gravity decreased by 11% and 22%, respectively. The actual and apparent specific gravity of the soil decreased by adding biochar to the soil. Decreasing the depth of irrigation water and increasing water salinity increased the amount of phosphorus, potassium, nitrogen, pH and EC of the soil. The amount of irrigation water had no significant effect on the apparent and actual specific gravity, however, the salinity of the irrigation water caused a significant increase in the apparent and actual specific gravity of the soil. Although the addition of biochar to the soil increased the nutrients required by plants in the soil, high amounts of biochar in the soil should be used careful, because the addition of this organic matter to the soil at high levels increased soil EC significantly. Based on the findings derived from the research, the utilization of biochar is recommended as a viable approach for enhancing both the chemical quality and productivity of nutrient-poor and sandy soils.
Soil science
J. Al-Jomah; A. Halajnia; A. Lakzian; A.R. Astaraei
Abstract
Introduction
Saline soils resulting from natural and/or anthropogenic processes are very diverse and widely distributed under all climates. Soil salinity as a serious environmental problem has negative effects on plant growth and development in arid and semi-arid as well as humid regions. Since increasing ...
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Introduction
Saline soils resulting from natural and/or anthropogenic processes are very diverse and widely distributed under all climates. Soil salinity as a serious environmental problem has negative effects on plant growth and development in arid and semi-arid as well as humid regions. Since increasing global food security is a fundamental goal to feed the growing world population, it is necessary to develop suitable and efficient techniques for the rehabilitation of salt-affected soils and their exploitation. Chemical fertilizers are usually used to provide nutrients required for plant growth in order to increase crop yield, but application of these chemical components has negative environmental effects and reduces the quality of soils and agricultural products. The use of beneficial microorganisms (bacteria and fungi) as fertilizers and biological amendments has a high potential to improve productivity in saline soils. The aim of this study was to investigate the effect of using Acidithiobacillus bacteria along with mycorrhiza on the production of some photosynthetic and biochemical metabolites in maize under salt stress and comparing it with control conditions.
Materials and Methods
To perform this experiment, a surface soil sample was collected from a depth of 30 cm from the campus of Ferdowsi University of Mashhad, and some physical and chemical properties of the soil were measured by usual laboratory methods. To prepare saline soil a mixture of four compounds MgSO4.7H2O, Na2SO4, NaCl, and CaCl2. 2H2O were used. The mycorrhizal fungus (Funneliformis mosseae) and mesophilic Acidithiobacillus bacteria species two types of bacteria, Acidithiobacillus thiooxidans PTCC No: 1692 (DSM 504) and Acidithiobacillus ferrooxidans PTCC No: 1646 (DSM 583), were purchased from Turan Biotechnology Company (Semnan Science and Technology Park) and Iran Microbial Scientific and Industrial Research Center (PTCC), respectively. In this research, the effect of biological treatments including: two levels of mycorrhiza (inoculation and non-inoculation), two levels of salinity (0.96 and 6 d/m) and four levels of Acidithiobacillus control (C), Acidithiobacillus thiooxidans (T), Acidithiobacillus Ferrooxidans (F), Acidithiobacillus thiooxidans and Ferrooxidans (T+F) were compared with each other on some photosynthetic and biochemical characteristics of Zea mays under greenhouse conditions in the form of a completely randomized design with factorial arrangement with three replications. 10 gr of salt mixture (this amount of salt was obtained to reach electrical conductivity of 6 in the pre-experiment) was added to 5 kg of soil and the soil moisture of the pots was kept for one month in the field capacity. Bacterial treatments were inoculated with 30 mL of cell suspension per pot (approximately 107 CFU mL-1). In the simultaneous use of two bacteria, 15 ml of each bacterial cell suspension (15+15) was added to each pot. Single-cross 704 variety of maize was grown in pots and soil moisture was maintained during the growth period in the field capacity by weighing. Chlorophyll a, b and carotenoid, concentrations of flavonoids, anthocyanins and proline and electrical leakage were measured in fresh leaf samples (third leaf on the stem).
Results and Discussion
The results showed that salinity decreased the percentage of root colonization and chlorophyll a and b content in leaves. Salinity decreased chlorophyll a, b and carotenoid in leaves by 27.9, 68.42% and 50%, respectively. Salinity increased proline concentration (42.62%), electrolyte leakage (33.30%), anthocyanins concentration (96.36%) and leaf flavonoids (84.73%) compared to control soil. Inoculation with mycorrhiza compared to no inoculation had a remarkable and significant effect on all investigated parameters in both saline and control soils. In saline soil, mycorrhizal inoculation reduces electrolyte leakage (56.75%) and increases chlorophyll a (2.3 times), chlorophyll b (6.6 times), carotenoid (1.3 times), proline concentration (24.39%), anthocyanins amount (24.07) and flavonoids (20.4%) in the plant. The effect of bacterial treatments on the investigated parameters in plants inoculated with mycorrhiza was greater than non-inoculated treatments. The effectiveness of the simultaneous application of both bacteria was greater than the effect of each of them alone. In saline soil, simultaneous inoculation of mycorrhizae with both bacteria species reduces electrolyte leakage (14.72%) and increases chlorophyll a (39.80%), chlorophyll b (106%), carotenoid (50%), proline concentration (10.12%), the amount of anthocyanins (14.17%) and flavonoids (4.06%) compared to mycorrhiza treatment alone. The results showed that these bacteria can probably be considered as helping mycorrhizal bacteria.
Conclusion
The objective of this study was to examine the impact of simultaneous inoculation of mycorrhizae and Acidithiobacillus bacteria on select photosynthetic and biochemical metabolites of maize subjected to salinity stress conditions. Confirming the results of other studies, the results of this research also showed the clear and distinct effect of mycorrhiza on increasing chlorophyll and producing metabolites effective in increasing plant resistance to salt stress. In addition, the results showed that although the use of each species of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans alone was effective on the measured parameters in both saline and control soils, the simultaneous inoculation of both Acidithiobacillus bacteria species and mycorrhiza had the greatest effect on increasing chlorophyll, production of proline, anthocyanins and flavinoids and reducing electrolyte leakage and as a result, increasing tolerance to salt stress. In other words, these bacteria can be considered as mycorrhiza helper bacteria, whose activity can improve the function of mycorrhiza. On the other hand, mycorrhiza symbiosis may have increased the efficiency of these bacteria by changing the soil conditions and the environment around the roots. However, further greenhouse and field experiments with other plant species are necessary to confirm these findings.
Soil science
Y. Kooch; A. Shahpiri; K. Haghverdi
Abstract
Introduction
Forests, encompassing approximately 30% of the Earth's land area, hold significant ecological importance due to their rich biodiversity and the multitude of environmental services they provide. These ecosystems outperform other terrestrial habitats, making them invaluable to all life forms ...
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Introduction
Forests, encompassing approximately 30% of the Earth's land area, hold significant ecological importance due to their rich biodiversity and the multitude of environmental services they provide. These ecosystems outperform other terrestrial habitats, making them invaluable to all life forms on our planet. The destruction of forest habitats and changes in land use patterns exert significant impacts on the variability of soil quality indicators. The consequence of forest degradation encompass various adverse consequences, including the destruction of wildlife habitats, climate change, global warming, diminishing plant and animal biodiversity, and reduced water conservation capacity. Extensive research has been conducted to investigate soil quality in diverse land uses within temperate regions. However, there is a noticeable scarcity of studies focusing on semi-arid regions. It is imperative to note that a comprehensive and practical assessment of soil condition necessitates the simultaneous measurement of physical, chemical, and biological indicators. Such an integrated approach ensures a thorough and effective evaluation of soil quality. The primary objective of this study was to assess the impact of various land uses, namely natural forest (C. betulus - P. persica), plantation (Q. castaneifolia), garden, rangeland, and agricultural lands (rice), on the physical, chemical, and biological properties of the organic and mineral soil layers. Specifically, the investigation focused on the evaluation of fauna and flora, microbial communities, and enzyme activities. The study was conducted in the semi-arid region of Kajur Nowshahrmourd.
Materials and Methods
To achieve this objective, contiguous sections of the study area were carefully chosen, ensuring minimal variations in height above sea level, percentage and direction of slope. Subsequently, three slice of one-hectare dimension plots (100 × 100) were selected within each study habitat, with a minimum distance of 600 meters between them. From each one-hectare plot, four leaf litter samples and four soil samples (30 cm × 30 cm, 10 cm depth) were collected and transported to the laboratory for analysis. In total, 12 litter samples and 12 soil samples were collected from each of the habitats. The soil samples were divided into two parts: one part was air-dried and then passed through a 2 mm sieve for subsequent physical and chemical testing, while the other part was stored at 4 degrees Celsius for biological assessments. One-way analysis of variance tests were employed to compare the characteristics of the organic layer and soil among the studied habitats. Furthermore, Duncan's test (P>0.05) was utilized to compare the average parameters that exhibited significant differences among the different habitats.
Results and Discussion
The findings derived from this investigation underscore the substantial variability in organic layer characteristics across different vegetation types. Natural forests emerged as the most prominent in terms of thickness, nitrogen content, and calcium concentration, whereas agricultural areas exhibited the lowest values. Grassland areas displayed the highest carbon content and carbon-to-nitrogen ratio, while agricultural and natural forest areas demonstrated comparatively lower values. Agricultural lands demonstrated elevated bulk density and sand content, whereas natural forests exhibited the lowest values. Notably, natural forests showcased the highest porosity, aggregate stability, silt percentage, and macro- and micro-aggregate quantities, while agricultural areas presented the lowest values. Chemical analysis of the soil indicated that natural forests recorded the highest values for most chemical characteristics, while agricultural lands displayed the lowest values. Biological attributes generally exhibited the highest levels in natural forests and the lowest levels in agricultural areas. Specifically, the abundance and biomass of epigeic and endogeic fauna did not exhibit significant differences among different land uses during the summer season. Managed forests demonstrated the highest values for moisture content, basal respiration, substrate-induced respiration, and microbial biomass carbon. Conversely, agriculture exhibited the lowest values in these regards. The microbial biomass carbon-to-nitrogen ratio was highest in agricultural areas, while natural forests displayed the lowest value. Natural forests displayed the highest values for most nitrogen transformation characteristics, whereas agricultural areas exhibited the lowest values. Nitrogen nitrification and mineralization showed a decreasing trend across different land uses during the summer and autumn seasons. The type of vegetation cover also significantly influenced the variability of soil ammonium and nitrate levels.
Conclusion
Based on the results obtained from this study, it can be inferred that the preservation and conservation of natural forest cover should be given utmost importance. Additionally, in degraded areas, the establishment of woody vegetation can serve as a viable approach for the restoration of ecosystems with similar ecological conditions. Furthermore, the presence of tree covers, specifically C. betulus and P. persica, is of greater significance compared to rangeland and agricultural land uses in enhancing soil fertility and creating favorable biological conditions. As a result, this research provides valuable insights into the impact of different land uses on the characteristics of the organic and mineral soil layers in mountainous habitats. The information obtained can be instrumental in guiding natural resource managers and offering practical assistance in decision-making processes.
Soil science
T. Nazari; M. Barani Motlagh; S.O. Rastegar; M.H. Sedri
Abstract
IntroductionPhosphorus is an essential element for all living organisms, and it cannot be replaced by any other element. Phosphorus has however a limited resource, and it is estimated that the extracted phosphorus resources (Apatite) will last for another 50 to 100 years. One of the most widely used ...
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IntroductionPhosphorus is an essential element for all living organisms, and it cannot be replaced by any other element. Phosphorus has however a limited resource, and it is estimated that the extracted phosphorus resources (Apatite) will last for another 50 to 100 years. One of the most widely used technologies for recycling phosphorus is the precipitation of phosphorus from sewage sludge and leachate. Phosphorus Recovery as struvite (NH4MgPO4.6H2O) from sewage sludge has attracted special attention due to its potential for use as an ecological and slow release fertilizer. Struvite is a white, grain-like solid, odor-free and sludge–free ingredient, composed of magnesium, ammonium and phosphate at equal molar concentrations. Therefore, this study is designed to examine the effect of struvite replacement with triple superphosphate fertilizer on some physiological parameters and phosphorus availability in wheat plants in calcareous soils deficient in phosphorus. Methods and MaterialsSoil with phosphorus deficiency was collected from 0-30 cm depth under arable lands of Hajjiabad-e Seyyedeh located in Ghorveh township, Kurdistan Province, Iran. The soil was air-dried and ground to pass through a 2-mm sieve, followed by laboratory analysis to determine its physico-chemical properties. The struvite used in the research was obtained by optimizing the three main factors of sulfuric acid concentration, solid-to-liquid ratio, and time for the leaching process, and the three key factors of Mg:P ratio, N:P ratio and pH for the precipitation process by Response Surface Methodology. To achieve the aim of this study a factorial experiment was carried based on completely randomized design with 4 replications. The factors included the application of different proportions of struvite replaced with triple superphosphate (S0:P100, S25:P75, S50:P50, S75:P25 and S100:P0) and 4 levels of phosphorus (0, 50, 100 and 150 kg TSP ha-1) and a total of 54 pots. The application rate for struvite was calculated based on total phosphorus (P2O5). Then 10 wheat seeds were planted in each pot at 2-cm depth which after plant emerging and greening, declined to 4 plants in each pot. The pots were randomly moved twice a week during the growth period to eliminate environmental effects. Irrigation and weeding operations were applied by hand. Plants were harvested 60 days after planting (beginning of flowering), washed with distilled water and dried 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. Phosphorus concentrations in plant extracts were measured by the molybdenum vanadate or yellow method and chlorophyll content (a, b and ab) and carotenoids using the Arnon method. The statistical results of the data were analyzed using SAS software and LSD test (at 5% level) was used for comparing the mean values. Results and DiscussionBased on the obtained results, all the investigated treatments and their interactions were significant at p<0.01. However, the interaction effect of fresh weight shoots and height was significant at p<0.05. The comparison of the average data showed that the highest amount of fresh weight shoots (7.79 g pot-1), dry weight shoots (1.130 g pot-1) and height (29.66 cm) was obtained from the application of S75:P25 150 kgTSP ha-1. By use of struvite instead of triple superphosphate fertilizer, the phosphorus concentration and uptake of wheat increased at all three fertilizer levels, so that the highest phosphorus concentration (0.174%) was obtained from S75:P25 150 kg TSP ha-1. However, there was no statistically significant difference for S100:P0 (0.169%) treatment. The highest amount of phosphorus uptake in wheat with an average of 0.197 g pot-1 was obtained from the S75:P25 treatment (150 kg TSP ha-1), compared to the treatment of 100% struvite (S100:P0) and 100% triple superphosphate fertilizer (S0:P100) with the averages of 0.158 and 0.109 g pot-1, respectively, showing 19.79 and 44.67 percent increase. Also, the results showed that the treatment of 150 kg TSP ha-1 100% struvite (S100:P0) compared to 100% triple superphosphate fertilizer (S0:P100) increased the amounts of chlorophyll a, b, ab and carotenoids by 7.78, 3.82, 6.44 and 6.84 percent, respectively. ConclusionDespite struvite's low solubility, it is a highly soluble phosphorus fertilizer for plants . However, the reasons for this apparent contradiction and also the specific mechanisms of struvite dissolution are still unclear. Hence, further accurate measurements at different pH and EC conditions with different physical and chemical properties of soil studying phosphorus fractionation in soil will help to better understand the use of struvite. Therefore, it is recommended to optimize the timing and application rate of struvite in relation to the demand for different agricultural and garden crops.