Effects of Long-Term Compost and Fertilizer Application on Soil Phosphorus Status Under Paddy Cropping System

Abstract

External phosphorus (P) fertilization in intensive cropping systems often exceeds P demand by crops, which leads to P accumulation in soils. Levels of different pools of soil P have been affected not only by soil properties and climatic condition but also by rate and type of P applied. This experiment was conducted to investigate the long-term applications of compost and chemical fertilizer on soil phosphorus status in paddy cropping system after addition of compost and chemical fertilizers for 34 years in rice monoculture production at National Youngnam Agricultural Experiment Station, Miryang, Korea. Four different treatments of soil amendments were selected in this study: control, compost application, NPK (nitrogen–phosphorus–potassium) fertilizer application, and compost plus NPK fertilizer application. Phosphorus status varied with the long-term applications of compost and fertilizers, and the compost plus NPK fertilizer treatment significantly increased total P in soil. Available P was increased in the treatments that received chemical fertilizers. Applications of compost and chemical fertilizers increased organic P fraction but the ratio of organic P to total P declined with application of compost or chemical fertilizers. Phosphorus-fixation was significantly increased due to the long-term application of compost and chemical fertilizers. The P fixation was highest with iron (Fe) than with aluminum (Al) and calcium (Ca) in the paddy soil. The highest Fe-P content occurred in the compost plus NPK fertilizer treatment. These results represented that the higher level of P remaining in the soil is accumulated by long-term annual application of compost and chemical fertilizers than by that of chemical fertilizer, and P accumulation might be a gradual saturation of the P-sorption capacity.