Effect of Different Nitrogen Rates on Nitrogen Utilization and Residual Soil Nitrate of Spring Maize

The environmental problem caused by excessive use of nitrogen fertilizer is becoming a very important issue and rational use of nitrogen fertilizer has become the focus of concern increasingly. In order to provide evidence for reasonable use of nitrogen fertilizer,this paper analyzed the effects of nitrogen level on spring maize nitrogen utilization and soil nitrate nitrogen residual. With 5 level of nitrogen rates(0,50,100,200 and 300 kg.hm-2),this experiment were conducted at Tongzhou District,Beijing. The effects on spring maize production,nitro-gen use efficiency,nitrogen balance and nitrate-nitrogen accumulation in soil were discussed in this paper. The results show as following:(1) the highest spring maize yield reached to 9 006.4 kg.hm-2; the nitrogen use efficiency ranged from 19.7% to 25.8% under different rates of nitrogen fertilization,which reached the highest 100 kg.hm-2 when 100 kg.hm-2 was applied; (2)the nitrogen uptake by spring maize increased with the nitrogen fertilizer increasing and surplus nitrogen in soil profile dominated the residual N. Despite apparent nitrogen loss was a small part of nitrogen surplus,the apparent nitrogen loss significantly increased with the nitrogen fertilizer increasing; (3)The residual Nmin accumulated increased significantly with the nitrogen fertilizer increasing in 180 cm soil profile,which reached to the highest value 195 kg.hm-2 at the rate of 300 kg.hm-2 level. The nitrogen at the rate of 100 kg.hm-2 could satisfy the spring maize demand. The environment would be threatened when the nitrate was cumulated in the soil at the rate of 200 and 300 kg.hm-2.