Phosphorus risk in an intensive agricultural area in a mid-high latitude region of China

• We studied the mechanism for variation of the soil phosphorus in the Sanjiang Plain in 11a.
• A remote-sensing driven model was used and has a good performance.
• Land use conversion and excessive fertilization are two key inducements to phosphorus risk.
• The areas where phosphorus leaching may occur are increasing remarkably.

The content and status of phosphorus (P) in agricultural soil have become critical environmental concerns because of the risk of excessive P reaching adjacent water bodies through leaching or runoff. The Sanjiang Plain, an important commercial grain base, is the largest swampy low plain in a mid-high-latitude region in China. The increasing risk of P leaching threatens the area's ecology and agricultural security, particularly because there have been more than 60 years of build-up of P in the soil as a result of intensive agricultural development. A remote sensing-driven model was used in this study to simulate the total phosphorus in the Sanjiang Plain soil from 2000 to 2010. A grid-random sampling method was employed to test the validity of the model in a typical in situ experimental area. Meanwhile, spatial analysis methods were used to analyze model outputs. The results show a significantly increasing trend in the area with higher concentrations of P in the Sanjiang Plain, phosphorus accumulation in the soil and an increasing area at risk of phosphorus leaching; among all land use types, cultivated land and water bodies were observed to have a higher phosphorus risk. We conclude that the growth in farmland converted from forest or wetland and the use of excessive fertilization to maintain high crop productivity are the two principal factors resulting in the growing concentration of soil P. The risk of higher phosphorus in the study area will pose a serious threat to the quality of both surface and ground water, which has important ramifications for future agricultural management and non-point source control in this agricultural area of the mid-high latitude region.