Difference in Available Phosphorus by Soil Depth In Drained Paddy Fields with Combined Application of Mineral and Compost Fertilizers

For higher self-sufficiency in soybean production, conversion of paddy to upland fields is recommended in Korea. This study aimed to investigate the effect of mineral (NPK) and compost fertilizers on the P availability in soils of drained paddy fields (DPF). Soils of paddy fields (PF) and DPF were collected by depths, and the properties, including pH, electrical conductivity, organic matter (OM), available P, etc., were measured. Soil OM in the topsoil of two fields treated with combined fertilizers was higher than in control and NPK-alone treatments. As soil depth increased, OM content gradually decreased, especially more in DPF. Available P showed a similar trend, which represented the highly-dependent P state across the soil profile, more in DPF. Moreover, the higher available P in the topsoil of DPF than PF, indicating that the effect of compost additive was greater in DPF, which appears to be due to less P loss than in PF. Co-application of mineral and compost fertilizers would be a good practice to effectively manage soil productivity in DPF, but is still a need to improve nutrient retention, especially for P. Thus, appropriate soil management approaches should be established to achieve sustainable agriculture in DPF.