Effect of Phopshate Fertilizer and Manure on Crop Yield, Soil P Accumulation, and the Environmental Risk Assessment

Phosphorus （P） applied from fertilizer and manure is important in increasing crop yield and soil fertility; however, excessive uses of phosphate fertilizer and manure may also increase P loss from agricultural soils, posing environmental impact. A long term experiment was conducted on a calcareous soil （meadow cinnamon） in Hebei Province, China, from 2003 to 2006 to investigate the effects of phosphate fertilizer and manure on the yield of Chinese cabbage, soil P accumulation, P sorption saturation, soluble P in runoff water, and P leaching. P fertilizer （P2O5） application at a rate of 360 kg ha^-1 or manure of 150 t ha^-1 significantly increased Chinese cabbage yield as compared to the unfertilized control. However, no significant yield response was found with excessive phosphate or manure application. Soil Olsen-P, soluble P, bioavailable P, the degree of phosphorus sorption saturation in top soil layer （0-20 cm）, and soluble P in runoff water increased significantly with the increase of phosphate fertilizer and manure application rates, whereas the maximum phosphorus sorption capacity （Qm） decreased with the phosphate fertilizer and manure application rates. Soil Olsen-P and soluble P also increased significantly in the sub soil layer （20-40 cm） with the high P fertilizer and manure rates. It indicates that excessive P application over crop demand can lead to a high environmental risk owing to the enrichment of soil Olsen-P, soluble P, bioavailable P, and the degree of phosphorus sorption saturation in agricultural soils.