Organic and inorganic amendment of wetland paddy soil for five years: effects on phosphorus fraction dynamics

摘要

Soil phosphorus (P) fractions indicate the P-supplying capacity to plant, which could be affected by fertilizer management systems. Information regarding the changes in P pools under different fertilizer management systems is essential for the sustainability of the systems. We studied the effects of different fertilizer practices on P fraction dynamics and associated soil properties under wetland double rice cropping system. Soil samples were collected from four depths (0-5, 5-10, 10-15, and 15-20 cm) of a five-year field experiment that received four treatments: soil-test-based NPKS fertilizer (STB), 3 t ha-1 cow dung (CD) + NPKS as integrated plant nutrition system (IPNS) [CD+IPNS], 2 t ha~(-1) poultry manure (PM) + NPKS as IPNS [PM+IPNS] and P control. Different P forms (solution P, NaHC0_3 -extracted P, NaOH-extracted inorganic P, NaOH-extracted organic P, acid P, and residual P) and soil properties (phosphate-solubilizing bacteria, acid phosphatase activity, and organic carbon) differed significantly with fertilizer treatments and soil depths. Different P forms and soil properties were remarkably increased with PM+IPNS compared to STB and CD+IPNS and were mostly concentrated at the topmost layers. The correlation analysis showed strong positive correlations among different P forms and soil properties. Application of PM (2 t ha~(-1)) in each cropping season could supplement the P requirement of rice crop, maintaining P pools in the wetland paddy soils. Moreover, the application of PM will reduce chemical fertilizer use, farmers' fertilizer cost, and environmental pollution. Thus, PM could be effectively utilized as a P source for rice production.