[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.