Soil science
A. Barvar; N. Boroomand; M. Hejazi-Mehrizi; M. Sadat Hosseini
Abstract
IntroductionPhosphorus as a vital nutrient for plant growth and development, contributes significantly to processes like photosynthesis, energy production, and root development. In soil, phosphorus mainly exists as phosphate, though much of it is not accessible to plants. There are several methods for ...
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IntroductionPhosphorus as a vital nutrient for plant growth and development, contributes significantly to processes like photosynthesis, energy production, and root development. In soil, phosphorus mainly exists as phosphate, though much of it is not accessible to plants. There are several methods for providing phosphorus to plants: such as chemical, organic, and combination of chemical and organic phosphorus fertilizers. The chemical fertilizers rapidly supply plants with absorbable phosphorus. However, excessive use of the fertilizer can degrade soil quality and cause environmental pollution. Manure and compost as organic fertilizers release phosphorus slowly in the soil. In addition to providing phosphorus, they enhance the chemical and biological properties of the soil. Using combination of chemical and organic fertilizers can increase phosphorus availability, promote soil health, and improve the sustainability of agricultural production. Given the importance of understanding the various forms of phosphorus in the soil for better plant nutrient management, as well as evaluating the combined application of different levels of chemical fertilizers and animal manure on the different forms of phosphorus, this study was conducted to examine the impact of these two phosphorus sources on its dynamics in the soil. Materials and MethodsTo investigate the effects of mono-potassium phosphate (MKP) fertilizer on various forms of phosphorus in soil, a completely randomized factorial experimental design was conducted. The treatments included four levels of MKP fertilizer (0, 70, 140, and 210 kg ha-1) and two levels of cow manure (0 and 40 tons ha-1). The impacts of the treatments on soil electrical conductivity (EC), pH, organic carbon (OC), and different phosphorus (P) fractions (water-extractable, NaOH-extractable, HCl-extractable, NaHCO₃-extractable, Olsen-P, and residual P) were examined. After harvesting, soil samples were taken from a depth of 20 cm below the initial fertilizer application site to examine the different fractions of soil phosphorus. A composite soil sample was taken from each treatment and after being transported to the laboratory, air-dried and passed through a 2 mm sieve. Results and DiscussionOverall, the results indicated that the addition of MKP and cow manure increased the soil EC and organic matter content. MKP fertilizer and cow manure significantly influenced various P fractions in the soil. Organic carbon content notably increased in the presence of cow manure. However, the interaction of high levels of phosphorus and cow manure resulted in a decrease in soil electrical conductivity (EC). The highest and lowest P concentrations were observed in the water-extractable fraction and residual P fraction, respectively. Organic matter predominantly enhanced the concentration of various P fractions, particularly water-soluble P. Organic matter exhibited a positive and significant correlation with water-extractable P (0.57), NaHCO₃-extractable P (0.44), NaOH-extractable P (0.44), and HCl-extractable P (0.6). The most pronounced effect of organic matter was on the water-extractable fraction, where its interaction with the MKP levels of 0, 70, 140, and 210 kg ha-1 resulted in respective increases of 35%, 51%, 36%, and 62% compared to the control. The inclusion of manure in the soil boosts the levels of available, water-extractable phosphorus, as well as phosphorus extractable with bicarbonate and sodium, and also increases residual phosphorus. Furthermore, higher levels of monopotassium phosphate fertilizer enhance soil electrical conductivity and extractable phosphorus. However, in some instances, such as with acid-soluble phosphorus, they can lead to a decrease in the concentration. In general, the combined application of manure and monopotassium phosphate improved soil phosphorus content; however, their impact on other soil properties, such as pH and organic carbon may vary. ConclusionThe simultaneous use of chemical and organic fertilizers can had a significant positive effect on the availability of phosphorus in the soil. As highlighted in the text, animal manure enhanced phosphorus availability to plants due to its phosphorus content and its influence on soil phosphorus solubility. Additionally, the observed sequence of phosphorus concentrations in different soil fractions (water > sodium > bicarbonate > acid > residue) reflected the distinct effects of these phosphorus sources, which, when combined, can improve the availability of this nutrient. Another important consideration was the need for further research to determine the optimal levels of these fertilizers. This would help identify the most effective combination and application rates for improving soil fertility and boosting agricultural productivity. Overall, such studies enable farmers and researchers to develop more effective strategies for managing phosphorus in soil, thereby contributing to the maintenance of soil health and higher agricultural yields.
Z. Dianat Maharluei; M. Fekri; M. Mahmoodabadi; A. Saljooqi; M. Hejazi
Abstract
Introduction: Today, soil pollution is an important environmental issue that should be taken into account. Industrial activities cause pollution and accumulation of heavy metals in the soil. Soil pollution significantly reduces the quality of the environment and threatens human health. Heavy metals are ...
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Introduction: Today, soil pollution is an important environmental issue that should be taken into account. Industrial activities cause pollution and accumulation of heavy metals in the soil. Soil pollution significantly reduces the quality of the environment and threatens human health. Heavy metals are one of the most important pollutants in the environment, which has received a lot of attention in recent decades. Heavy metal pollution is a serious problem in developing countries and urban areas. Among heavy metals, lead is found in large amounts in the Earth's crust, which has several effects on human health and the environment. Lead is an essential element for the plant and one of the most important pollutants, which is toxic even at very low concentrations. Its presence in the culture medium has a negative effect on germination rate, water status in the plant, dry root weight and aerial part of the plant, photosynthesis, absorption of nutrients and enzymatic activity. Much research has been done to use alternative and modern methods to clean the environment of heavy elements. One way to stabilize heavy metals in the soil is to use biochar. Due to its cation exchange capacity and high specific surface area, biochar is able to reduce the pollution caused by organic pollutants and heavy metals, stabilize heavy metals and improve the condition of plants and soil in terms of pollution. The aim of this study was to investigate the effect of modified biochars rice husk and almond soft husk on lead desorption kinetics in contaminated calcareous soil. Materials and Methods: To conduct this research, a sufficient amount of soil from a depth of zero to 30 cm was collected from the farm of Shahid Bahonar Agricultural College in Kerman. Physical and chemical properties of the studied soil were measured after air drying and passing through a 2 mm sieve. To prepare the biochars (rice husk and almond soft husk), the residues, after collection, were air-dried and ground and then packaged in aluminum foil to limit the oxygenation process. They were then placed in an oven at 500 0C for four hours to produce a charcoal called biochar. Also, to prepare the modified biochar (NaOH and HNO3), one gram of biochar was added to 100 ml of distilled water and then 10 ml of concentrated acid (or 10 g of alkali) was added to it. Stirring at 60 0C for 24 hours. Finally, it was filtered using a centrifuge and washed several times with distilled water to neutralize the pH. The produced powder was dried at 70 0C for 24 hours. The lead desorption kinetics experiment was studied at several times (5, 15, 30, 60, 120, 240, 480, 960, 1440 and 2880 minutes) in two levels of biochar (0 and 4 wt %) and three levels of lead (0, 300 and 600 mg kg-1), which were incubated for 5 months under field moisture in a greenhouse. Results and Discussion: The kinetics results showed that the desorption of lead has the same pattern in all the time studied. Early rapid desorption occurred in the early desorption times (initial 30 minutes) followed by low-velocity desorption (8 hours) and finally, equilibrium was observed in the treated and control samples. The significant difference between the amount of lead released from the treated soils and control indicated a positive effect of both used engineered biochars on reducing lead desorption. The highest amount of lead desorption was observed in soil without biochar, while the lowest desorption rate occurred in treatments of rice husk and almond soft husk modified by sodium hydroxide. The application of modified biochar rice husk highly reduced lead desorption, compared to modified biochar almond soft husk. Conclusion: According to the results, the modified biochar with sodium hydroxide caused a significant reduction in lead desorption compared to other treatments, and this reduction was more in biochar rice husk than the almond soft husk one. It can be stated that rice husk biochar has been more successful than almond soft husk biochar due to its more porous structure and cation exchange capacity. Among the equations used for lead desorption estimation, the two-constant rate equation was selected as the best model for data fit due to high explanatory coefficient (R2) and low standard error (SE). According to the above, the use of biochar can be recommended as a modifier in lead contaminated soils.
