Effects of irrigation mode and N application rate on cotton field fertilizer N use efficiency and N losses

A field experiment was conducted to study the effects of different irrigation modes (drip irrigation and furrow irrigation) and different N application rates (0,240,360 and 480 kg N·hm-2) on the fertilizer N use efficiency and N losses in a cotton field in Xinjiang,Northwest China.The main N cycling pathways,such as the N uptake by cotton plant,NO3--N residual in soil,NH3 volatilization,NO3--N leaching,and nitrification-denitrification,were quantitatively monitored.Compared with furrow irrigation,drip irrigation increased the seed cotton yield,plant N uptake,and fertilizer N use efficiency significantly.The NO3--N residual in soil was significantly greater under furrow irrigation than under drip irrigation.With the application of fertilizer N,the N loss from NH3 volatilization under drip irrigation occupied 0.06%-0.14% of applied N,and was significantly greater than that under furrow irrigation.The N loss from NO3--N leaching under drip irrigation and furrow irrigation was 4.4% and 8.8% of the applied N,respectively.Compared with furrow irrigation,drip irrigation could significantly decrease the NO3--N leakage rate in leakage water.The nitrification-dinetrification loss under drip irrigation and furrow irrigation was 17.9% and 16.8% of the applied N,respectively.It was suggested that NO3--N leaching and nitrification-denitrification were the main N losses in the cotton fields of Xinjiang.