Interpretations of Elemental and Microbial Phosphorus Indicators to Understand P Availability in Soils Under Rice–Wheat Cropping System
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In order to address the scarcity of phosphorus nutrient reserves and the variations usually observed in the P nutrient storage in soils, a long-term experiment was targeted to assess the impact of integrated fertilizer schedule on soil phosphorus pools and ecophysiological ratios of phosphorus element. P-related soil enzymes like acid phosphatase activity and alkaline phosphatase activity were improved by 6.53–15.93% and 6.14–11.41%, respectively, over the recommended dose of fertilization. Addition of FYM recorded highest DHA (45.24 µg TPF released g−1 dry soil h−1) followed by wheat straw (41.25 µg TPF released g−1 dry soil h−1) and green manure (38.98 µg TPF released g−1 dry soil h−1). Integrated fertilizer schedule improved the microbial biomass phosphorus content by 8.97–29.72% as compared to 100% recommended dose through mineral fertilizer. In the integrated system, only 5–7% of the organic phosphorus was ascribed to microbial biomass, reflecting the accumulation of organic P forms. Higher ratio of DHA (0.20) and pyrophosphatase (0.23) to microbial C in integrated treatments confirmed that the enzyme activities were from extracellular enzymes released by microorganisms. The lower ratios of alkaline or acid phosphatase to pyrophosphatase indicate domination of phosphomonoesters in the P pools. These ratios are important to understand the P availability in soil systems especially under the integrated fertilization schedule.
KeywordsPhosphorus Long-term experiment Ecophysiological ratios INM Fertilizer Microbial biomass carbon
Authors are thankful to the Vice Chancellor, Bihar Agricultural University (BAU), Bhagalpur, Bihar, India, for providing necessary facilities. Special thanks go to the scientists associated with AICRP-IFS, Sabour, and ICAR—Indian Institute of Farming system Research, Modipuram.
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