Water Stress And Appropriate N Management Achieves Profitable Yields And Less N Loss On Sandy Soils

Attention is growing on the use of excessive nitrogen (N) and water in agricultural systems in Northwestern China because of lower water and N use efficiency. The soil NO3- dynamics and yield for cotton (Gossypium hirsutum L.) under the combined effects of drought and N additions, however, remain unclear. We investigated the effects of drought stress (367, 618, and 917mm yr(-1)) and N application levels (0, 150, 225, and 300 kg N ha(-1)) on soil nitrate nitrogen (NO3-) and yield in two years. Compared with optimum irrigation (917 mm), drought stress (618 and 367mm yr(-1)) significantly increased residual NO3- and decreased N loss. The 300 and 225 kg N ha(-1) treatment significantly increased NO3- content in most soil layers up to 200cm depth, but N loss was also at a maximum with 300 kg N ha(-1). Applying 225 kg N ha(-1) with moderate drought stress (618mm yr(-1)) resulted in the highest cotton yields (2952 kg ha(-1)) and plant N uptake (148.7 kg ha(-1)). Compared with the treatment of 150 kg N ha(-1) application with moderate drought stress (618mm yr(-1)), N agronomic use efficiency under the combination treatment of 225 kg N ha(-1) with moderate drought stress (618mm yr(-1)) had some decrease, but the difference was not significant. These results showed that reducing the N application rate to 225 kg N ha(-1) with moderate drought stress could be an optimum management practice for achieving high-yield, high-N use efficiency and could reduce soil N losses.