不同生育期持续干旱对玉米的影响及其与减产率的定量关系

为了探究不同生长阶段土壤水分含量持续下降过程对玉米生长发育和产量形成的影响,通过设置遮雨棚人工控水试验,分析不同生长阶段持续干旱条件下玉米株高、叶面积指数(LAI)、光合性能、地上生物量和产量等生理生态指标的动态变化.试验因素为控水时段和控水持续时间,从拔节普遍期开始分别控水20(T₁)和27 d(T₂),从抽雄普遍期开始控水20(T₃)和27 d(T₄),加上不控水对照(CK),共5个处理.结果表明: 持续干旱导致植株叶片卷曲、打绺,下部叶片衰老加快,对LAI影响较大,从而降低生物量的累积与籽粒产量.T₁～T₄处理结束时LAI分别为CK的74.9%、68.2%、60.5%和48.3%.玉米植株在经历持续控水后,叶片最大净光合速率(P_{n max})逐渐下降,T₁(T₃)和T₂(T₄)处理结束时P_{n max}分别降至CK的23%及不足10%,复水2周后,P_{n max}能恢复到CK的90%左右.T₁和T₂处理产量较CK分别下降18.5%和24.0%,T₃和T₄处理分别减产41.6%和45.8%.抽雄期持续干旱对玉米地上生物量及产量构成的影响大于拔节期干旱.干旱程度(D)能够定量表示土壤干旱状况,与玉米减产率存在线性定量关系,可通过计算D来预测玉米的减产情况.

Effects of continuous drought during different growth stages on maize and its quantitative relationship with yield loss

To investigate the influences of continuous decline of soil water content during different growth stages on the growth, development and yield of maize, artificial water control experiment with a rainout shelter were conducted, and the dynamic variations of several physiological and ecological indices of maize were analyzed, including plant height, leaf area index (LAI), photosynthesis characteristics, aboveground biomass, and yield. The experimental factors considered in this field experiment were the starting time and duration of water control. Rainfall was sheltered from jointing with duration of 20 (T₁) and 27 days (T₂) and from heading with duration of 20 (T₃) and 27 days (T₄) for each starting time. In total, there were 5 treatments in this field experiment, including the treatment of control check (CK). The results indicated that LAI was reduced by conti-nuous drought with leaves rolling, tresses and early aging of lower leaves, thus biomass accumulation and grain yield were reduced. At the end of each treatment of continuous drought, LAI was reduced to 74.9%, 68.2%, 60.5% and 48.3% of the CK LAI for the T₁ to T₄ treatments, respectively. After experiencing continuous water control, the maximum photosynthetic rate (P_{n max}) of leaf decreased gradually, with P_{n max} decreased to 23% of the CK P_{n max} for the treatment T₁ and T₃, and to less than 10% of the CK P_{n max} for the treatment T₂ and T₄ at the end of each treatment. Two weeks after re-watering, P_{n max} recovered to around 90% of the CK P_{n max}. Compared with CK, grain yield decreased by 18.5% and 24.0% for the T₁ and T₂ treatments, and by 46.1% and 45.8% for the T₃ and T₄ treatments, respectively. Continuous drought brought about more serious effects during heading period than during jointing period on aboveground biomass and yield components. The drought condition of soil could be represented by drought degree (D), which was linearly correlated with maize yield loss and could be used to predict the yield loss.