Modeling of soil available phosphorus surplus in an intensive wheat–maize rotation production area of the North China Plain

The excessive application of phosphorus fertilizer has caused available phosphorus (AP) surplus in cultivated soils. By using the Soil and Water Assessment Tool (SWAT), the soil AP surplus and its relationship with fertilization and environmental changes was estimated for the wheat-maize rotation production area in the Baiyangdian basin, which is a typical arid region in North China Plain. Due to the little runoff, the model was validated by the...