不同时期灌溉对华北平原春玉米穗粒数的影响

干旱胁迫是限制华北地区春玉米穗粒数形成的关键因子,探究不同时期灌溉对穗粒数的影响,对提高该地区春玉米产量和水分利用效率具有重要意义。在2014—2016年进行3年大田试验,设置拔节期、大口期、抽雄期、吐丝后15 d灌水和不灌水对照(CK),明确不同时期灌水对土壤水分变化、吐丝期穗位叶光合速率、穗粒数的影响及其相互关系。结果表明,在干旱和关键生育时期缺水的年份,灌水处理可以提高春玉米穗粒数,其中花期灌水较其他处理提高了1.4%~97.0%(2014年和2015年);而在多雨的2016年,各个灌水处理间穗粒数差异不显著。拔节期和大口期灌水促进了春玉米营养生长,提高了叶面积指数和生物量,但春玉米花期遭遇干旱胁迫仍会降低穗粒数。花期灌水处理在营养生长阶段受干旱胁迫影响,叶面积指数和生物量都降低,但保证了吐丝—授粉—籽粒建成关键阶段有充足的水分供应,其吐丝期光合速率较其他处理提高5.2%~32.8%。回归分析结果表明,吐丝期充足的土壤水含量可以显著提高春玉米光合速率(P=0.0034)和穗粒数(P=0.0137),但过多降水(降低光辐射)会影响光合作用及籽粒结实。因此,花期灌水是干旱年份保证春玉米穗粒数的重要措施。

Effects of irrigating at different growth stages on kernel number of spring maize in the North China Plain

Drought stress is the main limiting factor for kernel setting of spring maize in the North China plain(NCP).It is important to investigate the effects of irrigation at different growth stages on kernel number,which contributes much to improve grain yield and water use efficiency of spring maize in the NCP.A three-year field experiment was conducted from 2014 to 2016.Irrigating at V6,V12,tasseling,15 days after silking stage,and rain-fed treatments were set to evaluate the soil water change,ear leaf photosynthesis rate,kernel number per ear and their relationships.The results indicated that irrigating could increase kernel number in dry years,and irrigating at tasseling stage increased kernel number by 1.4%-97.0%compared with other treatments in 2015 and 2016.However,there were no significant differences among each treatment in kernel number in the rainy year of 2016.Irrigating at V6 and V12 stage increased vegetative growth of spring maize,including leaf area and biomass,whereas drought stress occurring at flowering stage still reduced kernel number.In irrigating treatment at tasseling stage,vegetative growth would be inhibited by drought,thus lowing leaf area index and biomass,but ensuring water availability during silking-pollination-kernel growth stage.Moreover,irrigating at tasseling stage increased photosynthesis rate(Pn)by 5.2%-32.8%than other treatments.Regression analysis suggested that high water availability could significantly increase Pn(P=0.0034)and kernel number(P=0.0137),but excess rainfall(low solar radiation)had adverse effect on kernel setting.Overall,irrigating at tasseling stage in dry years was a critical management to ensure kernel number of spring maize.