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.
Soil science
Z. Sokhanvar Mahani; N. Boroomand; M. Sarcheshmeh Pour
Abstract
IntroductionPhosphorus (P) is one of the most important elements necessary for plant growth and production of agricultural products. In calcareous soils, phosphorus deficiency is a general issue due to high pH, high soil calcium carbonate content, lack of organic matter and moisture. Phosphorus absorption ...
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IntroductionPhosphorus (P) is one of the most important elements necessary for plant growth and production of agricultural products. In calcareous soils, phosphorus deficiency is a general issue due to high pH, high soil calcium carbonate content, lack of organic matter and moisture. Phosphorus absorption capacity depends on different soil reactions such as: adsorption, sedimentation, stabilization and release. The speed and amount of plant available P depends on the soil reactions. Studying the kinetics of P release from soil is a good indicator to check the status of P uptake by plant. The kinetics of P release in soils is a subject of importance in soil and environmental sciences. The aim of this research was to investigate the kinetics of P release and derive the most suitable equation to describe the release of P from a calcareous soil when subjected to the acidification of rock phosphate and the addition of vermicompost. Materials and MethodsIn order to investigate the ability of acidified rock phosphate and vermicompost in P release, an experiment was conducted with 2 replications on a light-textured soil with low OC and Olsen-P (1.2 mg/kg). One hundred grams air dried calcareous soil was transferred into special containers and 5 treatments including: 1- control (soil), 2- rock phosphate, 3- acidified rock phosphate (20 CC nitric acid 0.1 N and 5 g rock phosphate), 4- vermicompost, and 5- acidified vermicompost (20 CC nitric acid 0.1 N and 5 g vermicompost) were applied. The treatments incubated two weeks in 20±2℃ temperature. The Kinetics of P release was studied by adding 20 mL of 0.5N NaHCO3 to, one gram of air dried treatments. Extraction times were considered to be 0.25 h to 256 h (in 11 times) based on the time of adding the NaHCO3 extractant until filtering. After adding the extractant, the samples were shaken and centrifuged. After filtering, the concentration of released P in samples were determined by spectrophotometer (Model: CE 292 Series2, ultraviolet). For higher accuracy in the measurements, acid-washed containers were adjusted based on the amount of soil moisture which was dried in the oven (105℃). Finally, the P release data were fitted to different kinetic equations. The effect of different fertilizer treatments on P release in specified times and then kinetics parameters were investigated and compared with the control. Results and DiscussionAddition of acidified and non acidified rock phosphate and vermicompost increased the amount and speed of P release in the calcareous soil. Six kinetic equations were fitted to describe the release of P in the period of 0.25 h to 256 h from the soil to evaluate the effect of the treatments. The highest release of P was in vermicompost and acidified rock phosphate treatment, which were an organic fertilizer and a source for preparing phosphate fertilizers. To describe the release rate, kinetic equations were used. The best equations were chosen by highest coefficient of determination (R2) and the least of standard error (SE). The zero, first, second order equations could not describe the release of P in the studied calcareous soil. The R2 value decreased from the zero to second order equation. The simplified Elovich equation described well the release of P from the soil with the average R2 of 0.79 and with the average SE of 0.4. Comparison of the average effect of the studied treatments with the control showed that the acidifed vermicompost and rock phosphate treatments increased the capacity and speed of P release compared to the control. On the other hand, acid addition has increased the capacity and speed of P release in the calcareous soil. ConclusionThe findings indicated an initial rapid release of P, which then decreased over time. Notably, the application of vermicompost and the acidification of the soil with rock phosphate resulted in a pronounced and accelerated release of P. Generally, organic fertilizer treatments exhibited a higher release of P compared to chemical fertilizer treatments. This observation is in accordnce with the findings of the data presented by Ghorbanzadeh et al. (2009), who explored the P release potential of bone meal. Their data demonstrated that the acidification of bone meal accelerated and enhanced P release. To further enhance the practical relevance of these results, it is recommended to conduct this research in the presence of plants.
