减氮适墒提高冬小麦旗叶光合潜力和籽粒产量

摘要

针对目前小麦高产栽培中大量投入氮肥引起的土壤板结、肥效降低等突出问题,2013—2014和2014—2015年度大田条件下设置自然降水(W1)、适墒(W2,70%±5%)、足墒(W3,80%±5%)3个水分处理和3个氮肥水平处理,即不施氮肥(N1)、减氮(N2,195 kg hm–2)和高氮(N3,270 kg hm–2),研究了不同水肥条件对冬小麦旗叶功能期内光响应曲线特征参数、水分利用效率和籽粒产量及其构成因素的影响。在W1和W2条件下, N2处理不同时期旗叶净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)的光响应曲线逐渐上升的幅度均高于N1和N3处理,胞间二氧化碳浓度(Ci)光响应曲线下降的幅度也大于N1和N3处理；在W3条件下, N2、N3光响应曲线的变化趋势相近。N2W2处理的旗叶光合参数在开花期最具优势,最大净光合速率为33.20μmol CO2 m–2 s–1,光饱和点达1507.4μmol m-2 s-1,分别比其他处理平均提高21.4%和9.5%,而光补偿点最低,表现出较高的光合潜能。连续两年产量结果显示, N2W2处理穗粒数和千粒重在9个处理中最高,差异显著(P <0.01)；籽粒产量在9500 kg hm–2以上,水分利用效率比W2和W3条件下的其他处理平均提高18.8%。上述结果表明,在适墒条件下施氮量从270 kg hm–2减少至195 kg hm–2,能充分发挥旗叶功能期的光合潜力,增加穗粒数和千粒重,提高籽粒产量。%This study aimed at seeking a possibility of reducing nitrogen (N) fertilizer input on getting high yield in wheat (Triti-cum aestivumL.) production in Huang-Huai Rivers Valley region. A field experiment was carried out with treatments of three soil moistures and three N application levels, to measure light-response curve parameters of flag leaf, water use efficiency and yield-component traits in the 2013–2014 and 2014–2015 growing seasons. The soil moisture treatments included no irrigation (W1), medium irrigation to 70%± 5% of soil relative moisture after jointing stage (W2), and well-irrigation to 80% ± 5% of soil relative moisture after jointing stage (W3). The N application rates were 0 (N1), 195 (N2), and 270 kg ha-1 (N3). Under W1 and W2 conditions, N2 treatment showed greater increases in net photosynthetic rate (Pn), stomatal conductance (Gs), and transpira-tion rate (Tr) of flag leaf and greater reduction rate of intercellular CO2 concentration (Ci) than N1 and N3 treatments. Under W3 treatments, N2 and N3 treatments had similar changing trend of light response curves. N2W2 was the most superior treatment in photosynthesis at anthesis stage, with the maximumPn of 33.20μmol CO2 m-2 s-1 and the light saturation point (LSP) of 1507.4μmol m-2 s-1, which were 21.4% and 9.5% higher than these averages of other treatments, respectively. In addition, N2W2 showed the lowest light compensation point, indicating its high photosynthetic potential. As a result, N2W2 had the largest kernal number and the highest thousand-grain weight across two years, with significant difference than other treatments (P < 0.01). The grain yield of N2W2 was more than 9500 kg ha-1, and the water use efficiency was 18.8% higher than that of other treatments under W2 and W3 conditions. These results suggest that reducing N application from 270 to 195 kg ha-1 under suitable soil mois- ture (medium irrigation) may increase wheat yield by enhancing the photosynthetic potential of flag leaf, which is a good man-agement of irrigation and fertilizer for high yield and high N use efficiency in Huang-Huai Rivers Valley wheat region.