Effects of controlled drainage and nitrogen fertilizer application on nitrogen migration and transformation in dryland

In order to study the effect of combination of controlled drainage and nitrogen application on nitrogen migration and transformation in dryland, a compared test-pit experiment was conducted in Yajiao Drainage and Irrigation Station in Hubei province. Nine treatments, named H30, H50, H100, C30, C50, C100, L30, L50 and L100 were studied with two factors, controlled drainage water table with three levels 30, 50 and 100 cm, and nitrogen application with three levels, high, conventional and low level. Nitrate and ammonia contents in the soil layers were measured. Results showed that under the conventional nitrogen application level, nitrate content was highest in the treatment C100, and lowest in the treatment C50. Under the low nitrogen application level, ammonia content was highest in the treatment L30. When the water table was same, ammonia content was lowest in the treatment H30, H50 and H100. When the nitrogen application level was same, ammonia content sorted by controlled water table was 30>50>100 cm. Under the same nitrogen application level, controlled drainage can improve the stability of the nitrogen. Under the controlled drainage condition, there was no need to increase or decrease the nitrogen application while the nitrogen stability was high. Under the conventional drainage condition, reducing the nitrogen application can promote the nitrogen stability.