EFFECTS OF FERTILIZATION ON NITRATE LEACH IN SOIL PROFILE AND ACCUMULATION IN CROPS AND YIELD RESPONSE IN NORTH CHINA

A four-year experiment was conducted in the meadow-cinnamon soil in the field and lysimeters of farmland on the foot of Mt. Taihang in North China to study the effects of fertilization on the distribution, dynamics and accumulation of nitrate in soil, nitrogen uptake by crops and the yields of winter wheat and summer maize that were rotated in this region. The results indicated: the nitrate content and its dynamics were directly correlated with the content of applied nitrogen, i.e, over applied nitrogen could easily lead to accumulation and leaching of nitrate in soil profile; the relationship between nitrogen and phosphorus was of both promotion and competition, i.e., proper application of phosphorus could improve nitrogen absorption by crops and reduce nitrate accumulation and leaching loss in root layers in soil. However, excessive appication of phosphorus could easily lead to nitrate accumulation and leaching loss in soil, especially in the lower layer of the soil. The competition between nitrogen and phosphorus was confined by the results of nitrate absorption by plants. Applying potassium remarkably reduced the nitrate accumulation and leaching loss in soil and improved the nitrogen uptake and yields of winter wheat and summer maize. Thus, the fertilizer contents and ratio of nitrogen, phosphorus and potassium are the key measures for reducing the nitrate accumulation and leaching loss in soil and improving crop yield in this area. The annual fertilization for winter wheat-summer maize were recommended as N2P2K2〔ρ A(N)=200 kg hm -2,ρ A(P)=32.5 kg hm -2,ρ A(K)=150 kg hm -2〕 in this region. Fig 6, Ref 13