Effects of Cropping Years on the Characteristics of Phosphorus Accumulation in Soil Profiles Under Greenhouse Vegetable Production

Based on the collective data from field surveys in intensive vegetable greenhouses in Shouguang,Shandong,the study was aimed to investigate the differences of phosphorus(P) input and soil P accumulation in greenhouse production with different cropping years,and compare the variation in the contents of total P(TP),organic P,inorganic P,Olsen-P and CaCl2-P in soil profile.The results showed excessive P accumulation was the typical characteristics in greenhouse field due to the use of animal manure and compound fertilizers with high P content and the removal of very P amount by vegetables,only accounted for 7.2% of total P input.Planting age increased the extent of P accumulation in greenhouse,and P surplus increased the concentrations of soil P in different forms,especially inorganic P,in soil profile.A positive correlation was significantly evident between the contents of Olsen-P,which indicated soil available P supply,and CaCl2-P,which was regarded as the index of P runoff;In the surveyed region soil CaCl2-P level significantly increased while soil Olsen-P content increased up to 80.4 mg·kg-1 in soil,which rapidly accelerated the high risk of P loss to environment.