Response of regional agricultural soil phosphorus status to net anthropogenic phosphorus input (NAPI) determined by soil pH value and organic matter content in subtropical China

Exploring the relationship between net anthropogenic phosphorus input (NAPI) and soil available P (SAP) content could inform applied issues related to environmental quality and agronomic productivity and increase our knowledge of element biogeochemical cycles. Here, the NAPI was estimated and the SAP content determined in eight counties in subtropical China from 1980 to 2010. It is suggested that the NAPI ranging 318-924 km−2 yr−1 in 1980 had increased substantially to 865-3601 km−2 yr−1 in 2010 across the eight counties, in which the P fertilizer application was estimated to represent the largest individual source of NAPI, accounting for an average of 36.1-74.6% of the NAPI. The NAPI in agricultural land (NAPIa) was the largest component of the NAPI, and 60.7-77.1% of the NAPIa accumulated in the upper 20 cm layer of agricultural soils, which significantly increased soil total-P (TP) and SAP contents. The increases in SAP, resulting from 10,000 kg P km−2 of the NAPIa (IOPNAPI), were estimated to be 1.61-4.36 mg P kg−1 in the counties. Both the correlation and variation partitioning analyses (VPAs) suggested that the soil pH and organic matter content (SOM) were the most important factors influencing the variations of IOPNAPI (determination coefficient: 72.5%). Therefore, the contribution of soil pH and SOM should be considered in enriching soil SAP levels and implementing optimal P management strategies to improving the agronomic effectiveness of P fertilization and further reduce the environmental risk of P loss in subtropical region.