The Comparison of Different Fertilizer Technologies on Nitrogen Leaching Losses and Nitrogen Use Efficiency in Rice Production——Taking Ningxia Irrigation Region as an Example

High N fertilizer and flooding irrigation applied to rice in anthropogenic-alluvial soil often result in N leaching and low use efficiency of applied fertilizer N from the rice field in Ningxia irrigation region in the upper reaches of the Yellow River. Sound N management practices need to be established to improve N use efficiency while sustain high grain yield levels and minimize fertilizer N loss to the environment. We investigated the effects of different fertilizer technologies on N leaching, N use efficiency and rice yield. The four fertilizer N treatments were CK (No nitrogen fertilizer application treatment); FP (Farmer's practice of application rate of urea at 300 kg N·hm-2, 60% used as base fertilizer, 20% as tillering fertilizer and 20% as booting fertilizer); SD (Controlled-release nitrogen fertilizer at 120 kg N·hm-2, all controlled-release fertilizer was applied as base fertilizer while transplant rice seedlings) and NB (Controlled-release nitrogen fertilizer at 120 kg N·hm-2, all controlled-release fertilizer was applied as base fertilizer in the seeding soil). The results showed that the SD and NB treatments could reduce the amount of nitrogen applied by 60% compared to FP but still maintain crop yields while substantially reducing N losses to the environment. The SD could significantly decrease the N leaching losses from the paddy field. Under the FP treatment, the leaching losses of TN, NO3-N and NH4+-N were 39.89, 26.22 kg·hm-2 and 5.49 kg·hm-2, respectively. Compared with FP treatment, the SD treatment could decrease the leaching losses of TN, NO3-N and NH4+-N by 18.97, 11.18 kg·hm-2 and 2.27 kg·hm-2. The nitrogen use efficiency of SD treatment was 55.7% which increased by 21.4% compared with FP treatment. NB treatment also could decrease nitrogen leaching losses TN, NO3-N and NH4+-N by 14.36, 10.14 kg·hm-2 and 1.84 kg·hm-2 and increase the N use efficiency by 15.7% compared with FP, but it increased nitrogen leaching losses of TN, NO3-N and NH4+-N by 4.61, 1.04 kg·hm-2 and 0.43 kg·hm-2 and decreased nitrogen use efficiency by 5.7% compared with SD. Considering the importance of sustaining high food production and minimizing negative environmental threat, we recommend the SD as an alternative management strategy for mitigating N loss in irrigated rice system in Ningxia irrigation region.