在“麦/玉/豆”套作模式下,以玉米杂交种川单418为材料,采用两因素随机区组设计,通过2年试验研究了不同施氮量0,90,180,270,360 kg纯N/hm2,和不同施氮时期即底肥:拔节肥:攻苞肥=5:0:5,3:2:5和5:2:3对玉米碳氮代谢的影响.研究结果表明,施氮量低于270 kg纯N/hm2时,随着施氮量的增加,玉米叶片、茎鞘的氮素和总糖积累以及碳氮代谢关键酶硝酸还原酶、谷氨酰胺合成酶、蔗糖磷酸合成酶活性表现出增加趋势,超过270 kg纯N/hm2时会起抑制作用,2年均以施氮量为270 kg纯N/hm2时表现最优,其次是施氮量为180 kg纯N/hm2,施氮量为180和270 kg纯N/hm2时显著或极显著高于对照.各施氮处理叶片C/N从拔节期至乳熟期平均下降速率分别为26％,25％,21％,23％,且当施氮量为270 kg纯N/hm2时茎鞘C/N保持较低水平,叶片乳熟期仍然保持高效合成能力,有利于产量形成.不同氮肥配比对碳氮代谢影响表现为3:2:5＞5:0:5＞5:2:3,氮肥后移(3:2:5)促进叶片和茎鞘糖、氮积累,增强硝酸还原酶、谷氨酰胺合成酶和蔗糖磷酸合成酶活性,与氮肥前移(5:2:3)相比差异显著.因此“麦/玉/豆”模式结合氮肥运筹能够协调并能明显改善玉米碳氮代谢,进而实现周年作物的可持续生产.综合总糖、氮素的积累以及碳氮代谢关键酶的表现,“麦/玉/豆”模式下以施270 kg纯N/hm2,基追比3:2:5为最佳氮肥运筹方式.%Effects of nitrogen application strategies which contained five different nitrogen application rates: 0, 90, 180, 270 and 360 kg N/ha and three different assigning proportions (basic N : jointing N: huge bellbottom N): 5 : 0 : 5, 3 : 2 : 5 and 5 : 2 : 3 on carbon and nitrogen metabolism of maize in wheat/maize/soybean relay intercropping system were studied by two factors randomized trials using Chuandan 418 material through two years' field experiment. Wheat/maize/soybean relay intercropping system which was a new planting pattern could increase grain yields greatly because of soybean nitrogen fixation, inter-specific nitrogen competition and facilitation and nitrogen transfer. The results showed that, the accumulation of total sugar and nitrogen of leaves and stem/sheath and also the activity of nitrate reductase, glutamine synthetase and sucrose phosphate synthase of ear leaves which were the key enzymes to the carbon and nitrogen metabolism increased with the increasing of nitrogen fertilizer application when the amount of nitrogen fertilizer was under 270 kg N/ha, however, the results were opposite while the nitrogen levels were beyond 270 kg N/ha. For two years, the amount of nitrogen fertilizer which was 270 kg N/ha had the optimal performance, and then came 180 kg N/ha, the results of nitrogen treatment which were 180 and 270 kg N/ha were significant or quite significant to the compared group. The average decreasing rate of C/N in leaves were 26%, 25%, 21%, 23%, respectively, but in stem/sheath, it remained a relatively low level when the amount of nitrogen fertilizer was 270 kg N/ha, leaves whose nitrogen fertilizer was 270 kg N/ha still had an efficient synthetic ability in milking stage, and also remained a relatively low level of C/N in stem/sheath. Different assigning proportions had different effects on carbon and nitrogen metabolism, that was, 3 : 2 : 5>5 : 0 : 5>5 : 2 : 3, it was obvious that the postponing of nitrogen application could improve the matter production, and also increase the activity of nitrate reductase, glutamine synthetase and sucrose phosphate synthase of ear leaves, it was significant compared to antedisplace-ment of nitrogen application. As a result, nitrogen strategies in combination with wheat/maize/soybean relay intercropping system can obviously improve the carbon and nitrogen metabolism of maize, and then, realize the sustainable crop production. In combination with matter production and the performances of the key enzymes, the best nitrogen application strategy was 270 kg N/ha and 3 : 2 : 5.
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