Document Type : Research Article
Authors
1 Department of Soil Science, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran
2 Department of soil science, Shahid Bahonar University of Kerman
3 Department of Horticultural Sciences, Faculty of Agriculture, University of Jiroft, Jiroft, Iran
Abstract
Introduction
Phosphorus is a vital nutrient for plant growth and development, contributing 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: chemical phosphorus fertilizers: These fertilizers rapidly supply plants with absorbable phosphorus. However, excessive use can degrade soil quality and cause environmental pollution. Organic fertilizers: Organic options such as manure and compost release phosphorus gradually. In addition to providing phosphorus, they enhance the chemical and biological properties of the soil. Combination of Chemical and Organic Fertilizers: Using both types of fertilizers together 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 fertilizer 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 Methods
To 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) and two levels of cow manure (0 and 40 tons/ha). 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 Discussion
Overall, 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 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. Overall, the combined application of manure and monopotassium phosphate improves soil phosphorus content; however, their impact on other soil properties, such as pH and organic carbon, may vary.
Conclusions
The simultaneous use of chemical and organic fertilizers can have a significantly positive effect on the availability of phosphorus in the soil. As highlighted in the text, animal manure enhances phosphorus availability to plants due to its phosphorus content and its influence on soil solubility. Additionally, the observed sequence of phosphorus concentrations in different soil fractions (water > sodium > bicarbonate > acid > residue) reflects the distinct effects of these phosphorus sources, which, when combined, can improve the availability of this nutrient. Another important consideration is 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 enhancing 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 improved agricultural yields.
Keywords: Mono-potassium phosphate, Phosphorus, Cow manure, Organic carbon, Olsen P
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