Effect of Nitrogen Application Rate on Crop Yield and the Soil Nitrate Nitrogen Accumulation in the Intensive Agriculture Region in North China

To optimize nitrogen fertilization rate in wheat-maize rotation system in the intensive agriculture areas of North China,the field experiment was carried out to study the effects of nitrogen application rate on soil nitrate nitrogen accumulation and crop yield. The results showed that the amount of nitrogen fertilizer application should be309 kg / ha to guarantee the highest yield of winter wheat. The best economic nitrogen rate for winter wheat was 291 kg / ha. The amount of nitrogen fertilizer application should be 213 kg / ha to guarantee the highest yield of summer maize. The best economic nitrogen rate for summer maize was 199 kg / ha. With increasing N application rate and planting years,nitrate N accumulation in the soil rapidly increased. Compared with the first planting year,soil nitrate accumulation of the treatment( nitrogen rate of 375 kg / ha in wheat season,nitrogen rate of 300 kg / ha in corn season) increased 56. 06% for wheat harvest and 62. 07% for maize harvest after the second planting year. The higher amount of nitrogen,100- 200 cm soil nitrate accumulation proportion of the total would be greater. Nitrogen rate of150 kg / ha in wheat and corn season,the nitrogen fertilizer use efficiency of wheat and corn would maximum,46. 61% and 37. 51% respectively. Considering the amount of nitrogen leaching risk and crop yield,it was advisable to suggest that the N application rate should be controlled within the range of 250- 300 kg / ha for wheat and150- 200 kg / ha for corn,respectively in intensive agricultural region of North China. This would guarantee high yields and prevent excessive accumulation of fertilizer N in the soil and reduce the risk of nitrate N leaching.