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
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
M. Amarloo; M. Heshmati Rafsanjani; M. Hamidpour
Abstract
IntroductionApplication of natural organic matter derived components, i.e. humic acid, as fertilizer is a suitable way to improve soil fertility and increase yield and quality of agricultural products. Many researchers reported positive effects of humic acid on water holding capacity, soil aeration, ...
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IntroductionApplication of natural organic matter derived components, i.e. humic acid, as fertilizer is a suitable way to improve soil fertility and increase yield and quality of agricultural products. Many researchers reported positive effects of humic acid on water holding capacity, soil aeration, root formation and development, microorganism activities, and availability of mineral nutrients in soil. Antagonistic interaction between soil phosphorus and some micronutrients, especially in calcareous soils, can cause micronutrients deficiency in plants. With regard to positive effects of organic compounds on bioavailability of mineral nutrients, it seems that humic acid can positively affect the phosphorus interaction with micronutrients. Therefore, investigation of the effects of humic acid incorporated into irrigation water, phosphate and iron fertilizers application, on nutrients concentration in plants and their interactions is considerable.Materials and MethodsThis study was carried out to investigate the effects of application of humic acid in irrigation water, and phosphate and iron fertilizers in soil, on corn growth and concentration of P, Fe, Mn, Zn, and Cu in corn tissues. To this aim, a factorial experiment was conducted based on completely randomized design, with three replications in greenhouse. The factors included humic acid in 0, 70, and 140 mg kg-1 levels, (7 times as fertigation during growth season; total use equal to 0, 490, and 980 mg kg-1 of soil, respectively), phosphorus (P, as monocalcium phosphate monohydrate) in 0 and 50 mg kg-1 levels, and Fe (as ferrous sulfate heptahydrate) in 0, 10, and 20 mg kg-1 levels. P and Fe treatments were mixed with 4 kg of air-dried soil (<2 mm in diameter) and filled to the pots. Six seeds of maize (Zea maye L. cv. Single cross 704) were seeded per pot, and three seedlings were finally kept and grown for two months. After harvest, fresh and dried weight of shoots were measured. The roots were accurately extracted from the soil, washed, dried at 65◦C, and weighed. Sample digestion and measuring concentration of P, Fe, Mn, Zn, and Cu were done according to conventional methods (P by a UV-Visible Spectrophotometer and metal elements by the GBS Savant Atomic Absorption Spectrometer). Statistical analyses were done by the IBM SPSS Statistics version 26 software.Results and DiscussionAccording to this study results, the main effect of humic acid, on P concentration and dry matter of shoots and roots, was statistically significant. In presence of P (2nd P level), 490 and 980 mg kg-1 humic acid levels significantly increased the mean of dry matter compared to blank while humic acid had no significant effect on means of shoots and roots dry matter in 1st level of P (no P application). Increasing humic acid level from 490 to 980 mg kg-1, significantly decreased mean of shoots dry matter. The interaction effect between humic acid and the other two factors exhibited statistical significance concerning root dry matter. The treatment combination of 50 mg kg-1 of P, 490 mg kg-1 of humic acid, and 20 mg kg-1 of Fe yielded the highest mean root dry matter, which was 97% greater than that of the control. The 2nd level of P significantly increased the means of shoots P concentration in all levels of humic acid and Fe factors, compared to those of the 1st P factor level. There was no significant difference between means of shoots P concentration in different levels of humic acid and Fe factors, at the 1st level of P factor, separately. On the other hand, at the 2nd level of P factor, significant differences were observed between the means of P concentration for both other factors (significant interaction between P and humic acid, and between P and Fe Factors). Applying humic acid could significantly increase the means of shoots P concentration at the 2nd level of P factor, but there was no significant difference between those of 490 and 980 mg kg-1 levels. About the effect of Fe factor on shoots P concentration, only 10 mg kg-1 level of Fe significantly increased it. The main effect of the P and humic acid factors and interaction of the P and Fe factor on roots P concentration, were statistically significant. Roots P concentration increased significantly by 490 and 980 mg kg-1 humic acid levels. A significant increase of roots P concentration was observed in the 1st P factor level and 10 mg kg-1 level of Fe compared to the blank, and in 50 mg kg-1 level of P, Fe factor had no significant effect on it. The results showed that humic acid could not improve P uptake by corn from the soil with low available phosphorus (Olsen extractable P lower than 4 mg kg-1). The humic acid factor had no significant effect on Fe concentration of corn shoots, but its main effect and its triple interaction, with two other factors, on Fe concentration of the roots were statistically significant. There was no significant difference between the means of roots Fe concentration at the 1st level of P factor (9 treatments, various levels of humic acid and Fe factors). The highest mean of root's Fe concentration was found in treatment of the highest level of each factor, significantly more than those of the most of other treatments. About the Mn concentration in corn tissues, the Mn concentration in shoots was significantly increased by P fertilizer application, and Mn concentration in roots was significantly affected and increased by 490 and 980 mg kg-1 humic acid levels. The means of Mn concentration of roots in 490 and 980 mg kg-1 humic acid were not significantly different. The Zn concentration of corn shoots was significantly affected by interaction of the P and humic acid factors as the highest mean of it was in 0 mg kg-1 of P and 980 mg kg-1 humic acid levels, and there was no significant difference between those of other levels. The Zn concentration of corn roots was significantly increased by P applying and affected by the interaction of humic acid and Fe factors. When humic acid was at zero concentration level, Fe application of 20 mg kg-1 significantly decreased the Zn concentration of corn shoots while with humic acid application (490 and 980 mg kg-1) no significant difference was observed between the means. This result showed that humic acid can decrease the antagonistic effects of Fe and Zn in soil. The Cu concentration in shoots was significantly affected by the P and Fe factors. Usage of P fertilizer significantly increased the Cu concentration of corn shoots; on the contrary, the 2nd and 3rd levels of Fe factor (Fe applications) significantly decreased Cu concentration in shoots of corn. Moreover, using humic acid could significantly increase Cu concentration of corn roots without any significant interaction with the other two factors.ConclusionThe findings suggest that in soils with very low available P, humic acid alone does not enhance the growth and dry matter yield of corn. However, the efficiency of phosphate fertilizer can be enhanced by applying humic acid fertilizer through irrigation water. Additionally, humic acid has been observed to mitigate antagonistic effects between P and certain micronutrients, as well as reduce antagonistic interactions among metal micronutrients. For the positive effect of humc acid on growth and adequate chemical composition of corn, concentration of 490 mg kg-1 humic acid is recommended.
Soil science
H. Hatami; A. Fotovat
Abstract
Introduction
Boron (B) has a dual effect on living systems, so that the concentration range within which B is changed from a nutrient to a pollutant is rather narrow. Although B plays essential roles in all living organisms, its long-term excessive uptake has adverse effects on either human beings or ...
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Introduction
Boron (B) has a dual effect on living systems, so that the concentration range within which B is changed from a nutrient to a pollutant is rather narrow. Although B plays essential roles in all living organisms, its long-term excessive uptake has adverse effects on either human beings or plants and animals. Furthermore, part of the B that can be used as fertilizer is highly soluble and easily leached into the soil profile leadsing to some problems such as decrease of fertilizer efficiency. Therefore, to improve agricultural productivity through its gradual uptake by plants, the increase of B adsorption in the soil solution is necessary. Many adsorbents have been used for the adsorption of B from aqueous solutions; however, layered double hydroxides (LDHs) have been considered as one of the most effective adsorbents as well as slow releaser fertilizers of inorganic anions such as nitrate, phosphate, etc. The formula of LDHs are typically denoted as [M1-x 2+M x 3+ (OH)2]x+ (An-) x/n .m(H2O), where M2+ and M3+ are divalent and trivalent cations, respectively, the significance of x is the molar ratio of M3+/(M3++ M2+) and An- is the intercalated anion. Although LDH materials are commonly prepared by combining two divalent and trivalent metals, more metals can be introduced in the brucite layer to achieve a large variety of composition and higher adsorption capacity. Stability of LDHs in soil can be affected by numerous factors (e.g. low molecular weight organic acids (LMWOAs)) leading to release of structural cations in addition to interlayer anion. However, there are scarce investigations that have evaluated the potential of ternary LDHs (e.g. Zn–Mn–Al LDH) in desorption of B (as interlayer anion) and release of Zn and Mn (as structural anions) in a simulated soil solution. Therefore, the objectives of this study were, i) to compare the desorption of B capacity of binary LDH (Zn–Al LDH) and ternary LDH (Zn–Mn–Al LDH) in the simulated soil solution, and ii) to investigate the effect of three different electrolytes (potassium nitrate, oxalic acid, and citric acid) on the release of Zn and Mn from synthesized LDHs.
Materials and methods
A modified urea hydrolysis method was employed to synthesize Zn–Al and Mn-substituted Zn–Al LDHs with Zn(+Mn)/Al molar ratio of 2. Herein the contents of Mn with respect to Zn corresponded to 2% and 10% molar ratio. Accordingly, the synthesized materials denoted as Zn–Al, Zn–Mn1 and Zn–Mn2 for the samples without Mn, with 2 and 10 mol% Mn with respect to Zn content. For investigation of B desorption at a concentration of 10 mM, 15 mL from equilibrium solutions were substituted with 15 mL of 0.03 M KNO3 and shaken for 240 min. Substitution was repeated four times and A modified urea hydrolysis method was employed to synthesize Zn–Al and Mn-substituted Zn–Al LDHs with Zn (+Mn)/Al molar ratio of 2. Herein the contents of Mn with respect to Zn corresponded to 2% and 10% molar ratio. Accordingly, the synthesized materials denoted as Zn–Al, Zn–Mn1 and Zn–Mn2 for the samples without Mn, with 2 and 10 mol% Mn with respect to Zn content. For investiigatigatingon of B desorption at a concentration of 10 mM, 15 mL from equilibrium solutions were substituted with 15 mL of 0.03 M KNO3 and shaken for 240 min. Substitution was repeated four times and B concentrations in extracts were measured by Azomethine-H method. Furthermore, the supernatant Zn and Mn concentrations were determined by GF-AAS (PG 900). This process was repeated for 1.25 mM oxalic acid and 1.25 mM citric acid to study the effect of these compounds on B desorption as well as release of Zn and Mn. B concentrations in extracts were measured by Azomethine-H method. Furthermore, the supernatant Zn and Mn concentrations were determined by GF-AAS (PG 900). This process was repeated for 1.25 mM oxalic acid and 1.25 mM citric acid to study the effect of these compounds on B desorption as well as release of Zn and Mn.
Results and Discussion
The adsorption and desorption isotherm were carried out to describe the distribution of B between the liquid and adsorbent. The isotherm data of synthesized LDHs were matched with Freundlich model. The values of 1/n in this model were found between 0 and 1 for all LDHs indicating favorable sorption of B on these compounds. The highest adsorption was observed for ternary LDHs (particularly Zn–Mn2) due to their higher specific surface area and also due to the ion exchange mechanism in combination with surface adsorption. However, the results showed that the percentages of B desorption by potassium nitrate, oxalic acid and citric acid were lower for Zn–Mn1 (19.4, 29.1 and 38.2%, respectively) and Zn–Mn2 (18.6, 28.2 and 35.9 %, respectively) than Zn–Al (30.8, 41.2 and 46.2%, respectively). This observation suggests that the type of LDH, B adsorption mechanism and background electrolyte can affect the amount of B desorption. Furthermore, after 4 successive desorption cycles, the concentration of Zn and Mn increased in the supernatants (particularly in organic acid electrolytes) suggesting dissolution mechanism possibility happened for the studied LDHs. Among the background electrolytes, citric acid was the most effective compound in releasing Zn and Mn, followed by oxalic acid and potassium nitrate. A reason for this such observations could be that with respect to chemical structure, citric acid by three carboxyl groups can form more chelate rings compared to oxalic acid, which contain two carboxyl groups. Therefore, it seems that B containing Zn–Mn–Al LDH may have potential to be used as a slow release fertilizer in soils to supply three essential elements, including B, Zn and Mn simultaneously. However, further studies are required to support such a hypothesis.
azadeh ehsaninezhad; ali abbaspour; hamidreza asghari; hamidreza samadlouie
Abstract
Introduction: Phosphor (P) is the second nutrient element after nitrogen mostly required by plant. P is the main component of nucleic acid, phospholipid, ATP and some coenzymes. The effectiveness of phosphate fertilizer application is only about 15% - 20% and 10 – 25%, based on the different references.Rock ...
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Introduction: Phosphor (P) is the second nutrient element after nitrogen mostly required by plant. P is the main component of nucleic acid, phospholipid, ATP and some coenzymes. The effectiveness of phosphate fertilizer application is only about 15% - 20% and 10 – 25%, based on the different references.Rock phosphate (RP) as a source of P is not expensive, but its availability of P is low. Solubility of RP can be increased by phosphate solubilizing microorganisms. Increasing RP solubility by microorganisms is due to the lowering of pH and/or organic acid excretion. Fungi have been reported to possess greater ability to solubilize insoluble phosphates than bacteria. Among the fungal genera with the phosphate solubilization ability, there are Aspergillus and Penicillium. Aspergillus Niger convert insoluble phosphates into soluble forms through the processes of acidification, production of organic acids, production of acid and alkaline phosphatases, and the release of H+ .These organic acids can either dissolve phosphates as a result of anion exchange or can chelate Ca, Fe or Al ions associated with the phosphates. The aim of this study was to investigate the effect of Aspergillus Niger and green manure on soil P solubility in the incubation conditions.
Materials and Methods: To investigate the effect of Aspergillus Niger and green manure on soil phosphorus availability, an experiment in a completely randomized design with three replications was conducted. The treatments were applied over a period of 70 days and were repeated at 3 incubations. The treatments were included C: control (50 g soil), As: Aspergillus Niger (50 ml/ kg), A: Green manure (1% weight of the soil), S: Sucrose (1 g/kg soil), P: Rock phosphate (150 kg/ha), As + A: Aspergillus niger + Green manure, As + S: Aspergillus Niger + Sucrose, As+P: Aspergillus niger + Rock phosphate, As + S + P: Aspergillus niger + Sucrose+ Rock phosphate , and As + A + P Aspergillus niger+ Green manure +Rock phosphate . Soils were air-dried and crushed to pass through a 2-mm sieve. Treatments were then applied to 50 g of soil and the treated samples were moistened to the field capacity (FC). The moisture of containers was kept near FC soil moisture content throughout the experiment by periodically weighing and replenishing evaporated water. At intervals of 7, 21, 35, 51 and 70 days, the samples were taken and after air drying, pH, EC, available soil phosphorus by Olsen method and soluble phosphorus were measured. The statistical analysis of all data obtained from the experiments was performed using the MSTAT-C software. The mean comparison was performed using Least Significant Difference (LSD) test at 5% level and drawing graphs using Excel software.
Results and Discussion: The results showed that all treatments had a significant effect on the measured parameters at 1% probability level. The effect of treatments and incubation Times on soil pH showed that all treatments were able to reduce soil pH. The greatest decrease was observed in Aspergillus Niger + Green manure (As + A) treatment that could reduce the pH by 0.59 unit. Usually, green manure decreases soil pH through decomposition and release carbon dioxide and organic acids. Aspergillus Niger also reduces pH and thus increases the solubility of soil phosphorus through the production of the metabolites and organic acids and microbial respiration. The effects of the treatments and incubation time on soil electrical conductivity showed that all treatments were able to increase soil electrical conductivity. Most of this increase was related to Aspergillus Niger+ Rock phosphate+ Green manure (As +P+ A) treatment .This increase was probably due to inorganic compounds found in green manure. The effects of the treatments and incubation time on soil available phosphorus and solube phosphorus showed that all treatments were able to increase them. Most of the soluble and available phosphorus amounts were observed in As +P+ A treatment and the amounts of increase resulting from this treatment for soluble and available phosphorus were 0/28 mg/l and 10/79 mg/kg, respectively. However, the green manure treatments and aspergillus alone increased soil soluble phosphorus, but with treatment of Aspergillus Niger (As) in green manure (A) observed that the amount of phosphorus in the soil solution was further enhanced. Organic acids resulting from the decomposition of organic matter by adsorption onto calcium phosphate surfaces and occupy the active sites such as nuclei for the formation of these deposits, prevent the growth of new crystals. These organic acids, in addition to the creation of the complex with calcium cations, reduce the activity.
Conclusions: The results of this study showed that use of phosphate solubilizing microorganisms and organic matter led to the significant decrease in pH and increase in electrical conductivity, dissolved phosphorus and available phosphorus in soil.. However, to obtain more accurate results, it is better to do a pot experiment as well.
