Distribution and Transformation of Soil Phosphorus Forms under Different Land Use Patterns in an Urban Area of the Lower Yangtze River Basin, South China

Understanding the phosphorus (P) cycle is essential for preventing soil P loss, improving environmental quality, and promoting sustainable agriculture, particularly in urban areas. In this study, a representative city of the lower Yangtze River Basin, Nanchang, was chosen to systematically explore the distribution and transformation of soil P forms, which were extracted by an improved SEDEX method and measured by a standard phosphorus-molybdenum blue method under three land use patterns. The contents of soil P forms were the highest in the dryland and the lowest in the paddy field, with total P accumulation in the upper wasteland and paddy field soils but in the lower dryland soil. The pH value and grain size affected soil P form distributions to a variable extent from one land use pattern to another. The transformation of soil P forms was weak in the wasteland. It was first found that some detrital limestone P (De-P) was transformed into exchangeable P (Ex-P) in the paddy field with authigenic calcium-bound phosphorus (Au-P) and organic phosphorus (OP) transformation, and the transformation between Ex-P and iron-bound phosphorus (Fe-P), Au-P, and between Au-P and OP existed in the dryland. Land use pattern was the dominant driver for the P distribution and transformation of soil P. This study highlights the critical role of land use patterns in affecting the P cycle of soils in urban areas and the importance of sustainable urban land management.