氮肥运筹对晚播冬小麦氮素和干物质积累与转运的影响

氮素平衡对干物质积累与分配的影响是农业生态系统研究的重要内容,在保障产量前提下减少氮肥施用量可减少环境污染与温室气体排放。以晚播冬小麦为研究对象,设置4个施氮量水平:0 kg/hm2(N0)、168.75 kg/hm2(N1)、225 kg/hm2(N2)、281.25 kg/hm2(N3),每个施氮量水平下设置2个追氮时期处理:拔节期(S1)、拔节期+开花期(S2),研究了氮肥运筹对晚播冬小麦氮素和干物质积累与转运及氮肥利用率的影响。结果表明:拔节期追施氮肥(S1)条件下,在225 kg/hm2(N2)基础上增施25%氮肥(N3)对开花期氮素积累总量和营养器官氮素转运量无显著影响;拔节期+开花期追施氮肥(S2)条件下,随施氮量增加,开花期氮素积累总量和花后营养器官氮素转运量升高;S2较S1显著提高成熟期籽粒及营养器官氮素积累量、花后籽粒氮素积累量及其对籽粒氮素积累的贡献率。同一施氮量条件下,S2较S1提高了成熟期的干物质积累量、开花至成熟阶段干物质积累强度和花后籽粒干物质积累量。同一追氮时期条件下,籽粒产量N2与N3无显著差异,氮肥偏生产力随施氮量增加而降低;同一施氮量条件下,S2较S1提高了晚播冬小麦的籽粒产量和氮肥吸收利用率。拔节期+开花期追施氮肥,总施氮量225kg/hm2为有利于实现晚播冬小麦高产和高效的最优氮肥运筹模式。

Differential effects of nitrogen managements on nitrogen, dry matter accumulation and transportation in late-sowing winter wheat

The elemental cycling of nitrogen plays a key role in agricultural ecosystem to ensure either food security or environmental sustainability. Bases on the premise of grain yield stability, cutting down proper part of N fertilizer application would largely decrease environmental pollution and significantly promote greenhouse gas emission reduction. In recent years, because of climate change, improvements of varieties, water conservation, delay of maize harvest and other factors, the area of late-sowing winter wheat increases continually. A reasonable field management of nitrogen fertilizer is therefore considered as an important measure to improve the yield of late-sowing winter wheat. Appropriate late sowing of winter wheat could extend growth period of previous maize, and reduce the consumption of water and fertilizer in winter wheat at early stage. In the Huanghuai Plain, seedtime postponing to mid-late October in winter wheat could mitigate the damage of frost on winter wheat to a certain extent. There are many researches which document the effects of temperature, light, moisture, density and other factors on carbon and nitrogen metabolism, yield and quality in late-sowing winter wheat. However, the influence of fertilizer management on nutrition absorption and dry matter accumulation in late-sowing winter wheat has been rarely reported. Meanwhile, no final conclusion has yet been reached on nitrogen application strategy in late-sowing winter wheat. Under field conditions, we here designed four treatments of nitrogen fertilizer application: 0 kg/hm² (N0), 168.75 kg/hm² (N1), 225 kg/hm² (N2), and 281.25 kg/hm² (N3), at two topdressing stages: jointing stage(S1), jointing and anthesis stage(S2). We found that that regulation effect of nitrogen application rate on dry matter accumulation changes due to nitrogen application time. The accumulation and transportation of dry matter and nitrogen,as well as nitrogen use efficiency of late-sowing winter wheat were carefully investigated. We also noted that elevating 25% nitrogen fertilizer rate on the basis of 225 kg/hm²(N2) had no significant influence on either the total nitrogen accumulation at anthesis or nitrogen transportation amount in vegetative organs when nitrogen fertilizer topdressed at jointing stage (S1). However, those variables increased when nitrogen fertilizer topdressed at jointing and anthesis stages (S2). Compared with treatment S1, nitrogen accumulation amount in grain and vegetative organs, nitrogen accumulation amount after anthesis and nitrogen distribution proportion were much higher in treatment S2. At the same nirogen fertilizer rate, the dry matter accumulation at maturity, dry matter accumulation intensity from anthesis to maturity and dry matter amount of grain were higher in treatment S2 than those in S1. While at the same nitrogen fertilizer topdressing stage, grain yield has no significant difference between treatment N2 and N3, but nitrogen fertilizer partial factor productivity declined after nitrogen fertilizer rate increased. Grain yield and nitrogen fertilizer recovery efficiency were higher in S2 than those in S1 when nitrogen fertilizer rate was identical. We therefore reasonably drew the conclusion that topdressing nitrogen fertilizer at jointing and anthesis stages with total nitrogen fertilizer application rate at 225 kg/hm² was the optimal nitrogen fertilizer management mode which could not only achieve high yield but also obtain high nitrogen fertilizer use efficiency in late-sowing winter wheat.