不同水旱轮作体系秸秆还田与氮肥运筹对作物产量及养分吸收利用的影响

【目的】通过研究不同水旱轮作方式下秸秆还田与氮肥运筹对作物产量、氮素吸收及氮肥偏生产力的影响，以期为秸秆还田条件下氮肥的合理施用提供理论依据。【方法】2013-2014年在湖北省孝南、松滋、应城等14个县（市、区）开展水稻-油菜和水稻-小麦2种轮作条件下秸秆还田与氮肥运筹田间试验。试验共设置5个处理，分别为氮肥习惯3次施用、氮肥习惯3次施用配合秸秆还田、高量氮肥3次施用配合秸秆还田、氮肥2次施用（后肥前移）、氮肥2次施用（后肥前移）配合秸秆还田。分析秸秆还田条件下不同氮肥运筹对水稻、油菜及小麦产量、生物量、氮素吸收量及氮肥偏生产力的影响。【结果】对比秸秆还田下的2种轮作模式，增施氮肥对稻油轮作系统作物产量、地上部生物量及氮素吸收量无显著影响，而其对稻麦轮作系统的各指标均有显著提高的作用。稻麦轮作下，高量氮肥3次施用配合秸秆还田相比较氮肥习惯3次施用水稻和小麦平均增产量为0.632和0.564 t·hm^-2，增产率分别达6.85%和10.67%；地上部生物量分别增加1.50和1.07 t·hm^-2，增幅分别达8.11%和9.06%。地上部氮素吸收量分别增加11.54和23.57 kg·hm^-2，增幅分别达7.88%和21.28%，稻麦周年氮素吸收总量增加35.11 kg·hm^-2，增幅达13.65%。氮肥2次施用配合秸秆还田处理产量和氮素吸收量可以达到或优于氮肥习惯3次施用处理的水平，且以稻麦轮作下效果更为明显，其中水稻和小麦季平均增产量分别为0.439和0.385 t·hm^-2，增产率分别达5.12%和7.63%；地上部氮素吸收量分别增加11.09和21.06 kg·hm^-2，增幅分别达8.26%和20.82%，稻麦周年氮素吸收总量平均增加32.14 kg·hm^-2，增幅达13.66%。就氮肥利用率而言均表现出氮肥的常量投入即可获得较高的氮肥偏生产力（水稻季均值范围52.03-59.29 kg·kg^-1，油菜季10.62-11.12 kg·kg^-1，小麦季33.63-36.20 kg·kg^-1），等氮量投入下秸秆还田效果要明显优于秸秆不还田，且秸秆还田条件下氮肥后肥前移可以提高氮肥利用率。稻油轮作下氮肥习惯3次施用配合秸秆还田相比较氮肥习惯3次施用、氮肥2次施用配合秸秆还田相比较氮肥2次施用水稻季氮肥偏生产力分别增加2.45和4.07 kg·kg^-1，增幅分别达4.36%和7.37%，油菜季分别增加0.36和0.49 kg·kg^-1，增幅分别达3.38%和4.62%；稻麦轮作下水稻季分别增加3.88和1.64 kg·kg^-1，增幅分别达7.46%和3.10%，小麦季分别增加1.60和1.93 kg·kg^-1，增幅分别达4.75%和5.65%。与氮肥习惯3次施用处理相比，氮肥2次施用配合秸秆还田处理在稻油轮作下水稻和油菜氮肥偏生产力平均分别增加5.68%和4.00%；在稻麦轮作下水稻和小麦氮肥偏生产力平均分别增加5.12%和7.63%。【结论】综合氮素利用效率来看，在秸秆还田条件下2种水旱轮作模式均可以通过调整氮肥的后肥前移以保证作物达到高产或稳产的目的，同时提高氮肥利用率。

Effects of Nitrogen Fertilization Managements with Residues Incorporation on Crops Yield and Nutrients Uptake Under Different Paddy-Upland Rotation Systems

【Objective】The effects of nitrogen (N) fertilization management on crop yield, total N accumulation and partial factor productivity were studied under the condition of returning residues in different paddy-upland rotations. 【Method】Field experiments were conducted in 14 counties (e.g., Xiaonan, Songzi, Yingcheng) of Hubei Province under rice-oilseed rape and rice-wheat rotation systems in the period of 2013-2014. Five treatments were followed as: 1) Conventional N fertilization in 3 times, 2) conventional N fertilization in 3 times with residues incorporation, 3) high N fertilization rate in 3 times with residues incorporation, 4) N fertilization in 2 times, and 5) N fertilization in 2 times with residues incorporation. Crop yields (rice, rapeseed and wheat), total N accumulation and partial factor productivity were analyzed among the treatments.【Result】 Crop yield, aboveground biomass and total N accumulation were not affected by high N application rate under residue incorporation in the rice-oilseed rape rotation but were significantly increased in the rice-wheat rotation. Compared with conventional N fertilization in 3 times for the rice-wheat cropping rotation, high N fertilization rate in 3 times with residues incorporation rice and wheat yield increments were 0.632 and 0.564 t·hm^-2 on average, with the increasing rates of 6.85% and 10.67%, respectively. Aboveground biomass increments were 1.50 and 1.07 t·hm^-2 on average, with increasing rates of 8.11% and 9.06%, respectively. Total N accumulation increments were 11.54 and 23.57 kg·hm^-2 on average, with increasing rates of 7.88% and 21.28%, respectively. Total N accumulation of rice and wheat increment was 35.11 kg·hm^-2, with increasing rate of 13.65%. N application at 2 times with residues incorporation would satisfy crop yield and total N accumulation compared with conventional N fertilization at 3 times. Specifically for the rice-wheat rotations, rice and wheat yield increments were 0.439 and 0.385 t·hm^-2 on average, with increasing rates of 5.12% and 7.63%, respectively. Total N accumulation increments were 11.09 and 21.06 kg·hm^-2 on average, with increasing rates of 8.26% and 20.82%, respectively. Total N accumulation increment was 32.14 kg·hm^-2 for the rice-wheat cropping rotation, with increasing rate of 13.66%. For N efficiency, regular application rate of N obtained high partial factor productivity of applied N (PFP_N, averaged values of PFP_N were 52.03 to 59.29 kg·kg^-1 for rice, 10.62 to 11.12 kg·kg^-1 for oilseed rape, and 33.63 to 36.20 kg·kg^-1 for wheat), partial factor productivity of applied N (PFP_N) with residues incorporation was better than that without residues incorporation for equal nitrogen rates, especially when we moved N fertilizer forward with residues returning. For rice-oilseed rape rotation system, Compared with conventional N fertilization at 3 times and N fertilization in 2 times, conventional N fertilization in 3 times with residues incorporation and N fertilization in 2 times with residues incorporation the PFP_N of rice increments were 2.45 and 4.07 kg·kg^-1 on average, with increasing rates of 4.36% and 7.37%, respectively. Oilseed rape increments were 0.36 and 0.49 kg·kg^-1 on average, with increasing rates of 3.38% and 4.62%, respectively. For rice-wheat rotation system, rice increments were 3.88 and 1.64 kg·kg^-1 on average, with increasing rates of 7.46% and 3.10%, respectively. Wheat increments were 1.60 and 1.93 kg·kg^-1 on average, with increasing rates of 4.75% and 5.65%, respectively. Compared with conventional N fertilization at 3 times, the PFP_N values of rice and oilseed rape would increase 5.68% and 4.00% under N Fertilization at 2 times with residues incorporation, respectively. For the rice-wheat rotation system, N application at 2 times with residues incorporation would increase the PFP_N values by 5.12% and 7.63% for rice and wheat, respectively.【Conclusion】With residues returning, moving fertilizer-nitrogen forward would achieve high and stable crop yield and enhance N efficiency under different paddy-upland rotations.