减量施氮下基肥后移对南方冬小麦产量和氮素利用效率的影响

Effects of postponed basal nitrogen application with reduced nitrogen rate on grain yield and nitrogen use efficiency of south winter wheat

过量施用氮肥导致氮肥利用率降低,环境风险加大.合理降低施氮量、优化氮肥运筹对于小麦高产高效栽培具有重要意义.本研究采用大田试验,以常规施氮方式(240kg N·hm^(-2),基肥:拔节肥:孕穗肥=5:3:2)为对照,研究了不同施氮量(240、180、150kg N·hm^(-2),分别用N_(240)、N_(180)、N_(150)表示)及基苗肥施用时期(基施、4叶期施、6叶期施,分别用L_0、L_4、L_6表示)对小麦产量和氮素利用效率的影响.结果表明:小麦籽粒产量随施氮量的降低而降低,但N_(180)与N_(240)处理相比无显著差异,而N_(150)处理显著降低;氮肥农学效率和吸收效率均以N_(180)处理最高.不同施肥时期间,L_4处理的籽粒产量和氮肥利用率最高.N_(180)四叶施肥(N_(180)L_4)处理的产量与对照无显著差异,但氮肥利用率显著提高.N_(180)L_4处理叶面积指数、旗叶光合速率、叶片氮含量、旗叶硝酸还原酶和谷氨酰胺合成酶活性、拔节后干物质和氮素积累量较对照未显著降低.适量降低氮肥用量配合基肥后移能够提高生育后期光合生产能力和氮素吸收同化能力,在保持高产的条件下实现氮素利用效率的同步提高.

Excessive nitrogen （N） fertilizer application has led to a reduction of nitrogen use efficiency and environmental problems. It was of great significance for highyield and highefficiency cultivation to reduce N fertilizer application with modified application strategies. A twoyear field experiment was conducted to study effects of different N application rates at basal and seedling application stages on grain yield and nitrogen use efficiency. Taking the conventional nitrogen application practice （240 kg N·hm^-2 with application at basal, jointing, and booting stages at ratios of 5：3：2, respectively） as control, a field trial was conducted at different N application rates （240, 180 and 150 kg N·hm^-2, N240, N180 and N150, respectively） and different application times [basal （L0）, fourth （L4） and sixth leaf stage （L6）] to investigate the effects on grain yield and nitrogen use efficiency. The results indicated that grain yield decreased along with reducing the N application rate, but it had no significant difference between N240 and N180 while decreased significantly under N150. Nitrogen agronomy and recovery efficiency were all highest under N180. Among different N application stages, grain yield and nitrogen use efficiency were highest under L4 N180L4 had no significant difference with control in grain yield, but its nitrogen use efficiency was significantly higher. The leaf area index, flag leaf photosynthesis rate, leaf nitrogen content, activity of nitrogen reductase and glutamine synthase in flag leaf, dry matter and N accumulation after jointing of N180L4 had no significant difference with control. In an overall view, postponing basal N fertilizer application at reduced nitrogen rate could maintain high yield and improve nitrogen use efficiency through improving photosynthetic production capacity and promoting nitrogen uptake and assimilation.