Influence of N and P Applications on Phosphorus Leaching in Salt-affected Soils of the North China Plain

Background and Objective: The reclaimed salt-affected soils of the North China plain are an important land resource. The primary objective of this study was to investigate the effects of long-term fertilization practices on phosphate leaching so that practical advice on phosphorous fertilizer applications could be provided to farmers. Results from this long-term study have implications for P accumulation and loss in salt-affected soils around the globe where saline soils are present. Materials and Methods: Phosphorus (P) accumulation and leaching in the salt-affected soils of the North China Plain for 24 years has been studied. The field experiment with different applications of P and nitrogen (N) began in 1983. Soil samples were collected from 4 layers (0-20, 20-40, 40-60 and 60-100 cm layer, respectively) after the harvest of maize in 2007. Results: The total P content tended to stabilize at 0.40-0.60 g kgG 1 in 0-20 cm layer with natural vegetation in the absence of P fertilizer. The content of reactive P increased significantly from 0.5-1 in 1970s to 6.40-8.60 mg kgG 1 in 2007 in the control plot. With application of fertilizers, the contents of total P and reactive P increased to 0.96 and 43.24 mg kgG 1 in the 0-20 cm layer, respectively. Both the application rate of P and N/P ratio influenced P leaching from 0-20 to 20-40, even to the 60-100 cm layer. Conclusion: Based on these results, it was suggested that P application rate at 135 kg P haG 1 is appropriate to maintain the P requirements by plants while minimizing P leaching.