Rapid expansion of greenhouse vegetable production (GVP) in China within the last three decades has been accompanied with intensive application of chemical and manure fertilizers, frequent irrigation, and year-round crop rotation. As a consequence, excessive P accumulation and availability have taken place in major Chinese GVP soils impairing the quality of the adjacent freshwaters by eutrophication through surface/subsurface P mobilization. Although studies have reported massive P accumulation in Chinese GVP soils, potential risk of soil P mobilization as a function of soil labile P content and physiochemical soil properties remains poorly documented. Hence, this study has aimed to address the three following objectives. (1) To document P leaching from Chinese GVP soils as a function of P bonding/availability. (2) To test the performance of the DGT P method as a strong predictor of soil solution P (PSol) mobility in 75 GVP samples covering a broad range of soil properties (3) To document the marked accumulation of P in Chinese GVP soils as a function of region, soil type, and duration of cultivation, and to investigate if subsoils can act as a filter to keep leachate concentrations to the surrounding below threshold values

Overall, very high P contents were measured in 75 representative Chinese GVP top soils (0-20 cm) with total P and Olsen P varying from 260 to 11,200 mg kg-1, and 5 to 740 mg kg-1, respectively. These large variations reflect the significant differences in vegetation history, intense fertilization, and soil types. In particular, longer history of GVP along with fertilization in larger quantities caused higher soil P availability and eventual risks of P mobilization from alkaline coarse-textured soils. Very high dissolved reactive P (DRP) concentrations with a mean of 3.43 mg L-1 were found in the leachates from P rich coarse-textured Tongshan soils. In contrast, DRP leaching from fine-textured Guli soils rarely exceeded the suggested environmental P threshold of 0.1 mg L-1. In accordance, a change-point Olsen P value above 41 mg kg-1 led to susbtantial DRP leaching from Tongshan soils. Of all soils in this area, over 80% were found at high risk for P mobilization.