华北冬小麦开花期补灌的增产效应及其影响因素

为阐明华北地区冬小麦开花期补灌增产效应及其影响因素,制定稳产节灌制度,于2007—2016连续10年进行了大田定位试验,研究在冬小麦拔节期灌水基础上,播前底墒、长期不同施氮及生育期降水等对开花期补灌增产效应及水分利用的影响。裂区设计,灌水量为主区,设春灌1次水(拔节期75mm,W1)和2次水(拔节期和开花期各75mm, W2) 2个处理;施氮量为副区,设6个水平,分别为0 (N0)、60 (N60)、120 (N120)、180 (N180)、240 (N240)、300 kg hm-2 (N300)。冬小麦开花期补灌增产效应受播前底墒影响显著,播前2 m土体贮水量越大开花期补灌增产率越小。施氮水平也显著影响开花期补灌增产效应,随着定位试验年限的增加,N0和N60处理土壤有机质和全氮含量逐年下降,从第6年开始开花期补灌的增产效应基本丧失。在足墒播种和正常供氮(施氮量不低于120kghm-2)条件下,开花期补灌的增产效应还受冬小麦生育期有效降水量的影响,尤其是拔节–开花期的有效降水量。开花期补灌增产率随生育期以及开花后的有效降水量的增加而降低。拔节–开花期有效降水量大于25.3 mm时,开花期补灌没有显著优化穗数、穗粒数、千粒重、生物量、收获指数等产量性状,最终增产不显著;此情景下,拔节期灌1次水(75 mm左右),即可在维持较高产量的前提下,降低耗水、提高水分利用效率,实现稳产与节水协同。本研究表明,华北平原冬小麦在足墒播种、施氮量不低于120 kg hm-2、拔节期灌水前提下,拔节–开花期有效降水量可作为开花期灌水与否的重要决策依据。

Yield-increasing effect of supplementary irrigation at winter wheat flowering and its influencing factors based on water and nitrogen coupling in north China

Facing the increasing water shortage in North China, new techniques for high-yield and less irrigation are urgently needed in winter wheat production. A 10-year successive field experiment was carried out from 2007 to 2016 to clarify the effects of soil water storage before sowing and effective precipitation in wheat growth duration on the yield-increasing efficiency of supplementary irrigation at flowering stage, as well as the interaction of irrigation with nitrogen (N) application rate. The objective of the study was to propose an applicable standard of irrigation for winter wheat in North China Plain. The plots were arranged in a split-plot design with the main factor of irrigation amount and sub-factor of N rate. On the condition that 75 mm water was given at jointing stage of wheat, the main-plots were assigned with supplementary water of 0 (W1) and 75 mm (W2) at flowering stage. The sub-plot treatments were N rate of 0 (N0), 60 (N60), 120 (N120), 180 (N180), 240 (N240), and 300 kg hm ^-2 (N300). The yield-increasing ratio of supplementary irrigation at flowering stage was negatively correlated (P < 0.05) with the water storage in 2 m soil body before sowing and influenced by soil N level. The soil organic matter and total N content of N0 and N60 declined gradually with the years of experiment, and no positive effect of W2 on yield was observed since the sixth year. Under the condition of adequate soil water before sowing and normal nitrogen supply (at least 120 kg hm ^-2), the effect of W2 on yield was also influenced by the effective precipitation during wheat growth, especially that from jointing to flowering stage. The yield-increasing ratio of W2 decreased with the increasing effective precipitation in wheat growing period. When the effective precipitation from jointing to flowering stage was more than 25.3 mm, W2 had no significant advantage on spike number, grain number per spike, 1000-grain weight, biomass, harvest index, and final grain yield, indicating that irrigation of 75 mm at jointing stage was available for water-saving, high water use efficiency and high yield level. In conclusion, under the condition of well soil water content before sowing, N application rate ≥120 kg hm ^-2 and irrigation at jointing stage, the effective precipitation from jointing to flowering might be considered as an important criterion to determine the necessity of supplementary irrigation at flowering stage of winter wheat in North China Plain.