冬小麦-夏玉米轮作产量与氮素利用最佳水氮配置

Optimum combination of irrigation and nitrogen for high yield and nitrogen use efficiency in winter wheat and summer maize rotation system

【目的】华北太行山前平原高产限水区冬小麦-夏玉米轮作体系中灌水施肥不合理的现象普遍存在,水资源浪费和农业面源污染严重。长期定位研究水氮配置对小麦玉米产量和氮素利用影响,可为该区优化水氮管理模式,充分发挥水氮协同增效作用提供依据。【方法】2006 2014年进行大田试验,采取裂区设计,灌水量为主区,施氮量为副区。小麦季灌水设春灌一次水(W_1,拔节水)和两次水(W_2,拔节水+开花水)两个处理;玉米季在小麦灌一次水基础上设限水处理(WL),在两次水基础上设适水处理(WS),限水和适水的灌水次数根据降水年型而定。两种灌水条件均设置6个施氮水平,分别为0(N_0)、60(N_(60))、120(N_(120))、180(N_(180))、240(N_(240))、300(N_(300))kg/hm^2。连续8年定位测定了小麦玉米产量、植株吸氮量。【结果】小麦玉米产量和植株吸氮量年际间差异均较大,相对而言,W_2(WS)产量和吸氮量的年际波动较小,一定程度上降低了不同年型气象因素的影响,达到稳产的效果。两种水分条件下N0和N60处理的作物产量和吸氮量除个别年份外都显著低于其余施氮处理。本研究的产量水平下(冬小麦7000 9500 kg/hm^2,夏玉米8500 11000 kg/hm^2)小麦玉米产量与其吸氮量呈显著线性正相关。小麦玉米8年平均产量和吸氮量在一定施氮范围内均随施氮量的增加而显著增加,但施氮达到120 kg/hm^2后产量不再显著增加,达到180 kg/hm^2后吸氮量不再显著增加,同一施氮水平的作物产量和吸氮量都表现W_2(WS)高于W_1(WL)。两种水分条件下小麦玉米的氮肥偏生产力、氮肥农学效率和氮素生产效率都随施氮量的增大而显著减小,但对同一施氮水平W_2(WS)高于W_1(WL)。冬小麦-夏玉米整个轮作体系氮肥累计表观利用率(一段时期内作物对肥料氮的累计吸收量与该时期施氮总量的比值)同样随施氮量的增加显著减小,一次水+限水条件下从N60+60的51.8%下降到N300+300的22.3%,两次水+适水从N_(60+60)的57.4%下降到N_(300+300)的24.6%。同一施氮水平的氮肥累计表观利用率两次水+适水都高于一次水+限水。【结论】冬小麦春灌两次水、施用N 120 kg/hm^2,夏玉米适水灌溉、施N 120 kg/hm^2的产量和吸氮量都达到最高水平,氮肥偏生产力、农学效率、累计表观利用率以及氮素生产效率也比较高,因此在一定时期内可作为当地小麦-玉米轮作体系适宜的水氮配置,周年产量可维持在1619 t/hm^2。

【Objectives】Inappropriate management of irrigation and fertilization is common in the winter wheatsummer maize rotation system in the piedmont plain of Taihang Mountain. Overuse of fertilizers and irrigation result in severe waste of water resources and agricultural non-point source pollution. Study on the appropriate water and nitrogen combination for high yields and N-fertilizer utilization will be necessary for profitable and sustainableagricultural production in winter wheat and summer maize rotation system in the region. 【Methods】A two-factor complete split plot field experiment was conducted for 8 successive years. The main plots were irrigation volumes：one irrigation in jointing stage（ W_1） and twice in jointing and flowering stages（ W2） for wheat,limited water（WL） and suitable water（WS） for maize. Subplots were consist of six N rates： 0（N_0）,60（N_（60））,120（N_（120））,180（ N_（180））,240（ N_（240）） and 300（ N_（300）） kg /hm-2. The yields and plant N uptakes of wheat and maize were measured. 【Results】The annual yields and N uptakes of wheat and maize varied significantly in all treatments.The annual differences of the yields and N uptakes were smaller in W_2 and WS treatments than in W_1 and WL ones for all the six N rates. Whatever the irrigation treatments,the yields and N uptakes in N_0 and N_（60） treatments generally were significantly lower than in the other ones. In the yield levels of 7. 0-9. 5 t / hm-2 for winter wheat and8. 5- 11. 0 t / hm-2 for summer maize,the grain yields were significantly and positively correlated with the N uptakes. 8-years ＇ average of yields and N uptakes in both wheat and maize were increased significantly with increased N rates,but no significant increase in yields when N rate exceeded 120 kg / hm-2 for yields nor in N uptake when N rate exceeded 180 kg / hm-2. For the same N rate,the crop yields and N uptakes in W_2 or WS were higher than in W_1 and WL. Under the two irrigation conditions,the partial factor productivities from N-fertilizer（ PFPN）,N-fertilizer agronomic efficiency（ NAE） and nitrogen utilization efficiency（ NUtE） were reduced obviously with the increase of N fertilizer rate. In the same N rate,all the three indices in W_2 and WS were higher than in W_1 and WL. The accumulative apparent N-fertilizer recovery efficiencies（ AANRE） in the wheat-maize rotation system were also decreased obviously with the increase of N rates. Under the condition of W_1＋ WL,the AANREs were decreased from 51. 8% in N_（60 ＋ 60） to 22. 3% in N_（300 ＋ 300）,and from 57. 4% to 24. 6% for W_2＋ WS. For the same N rate,the AANRE under W_2＋ WS was higher than that under W_1＋ WL. 【Conclusions】The peak yields and N uptakes are obtained with twice irrigation plus N rate of 120 kg / hm-2 for wheat and suitable irrigation plus N 120 kg / hm-2 for maize, and the partial production efficiency, agronomy efficiency and the cumulative agronomy efficiency of N fertilizer are all maintained at higher level. Therefore,under the annual grain yield target of 16-19 t / hm-2,the optimal combination of water and nitrogen for winter wheat and summer maize is twice irrigation plus N120 kg / hm-2 in the piedmont plain of Taihang Mountain over a certain period of time.