Crop water productivity (CWP), irrigation water productivity (IWP), actual seasonal basal crop coefficient (K_ab), and actual crop evapotranspiration (ET_a) are essential parameters for accurate estimation of crop water requirement to prevent irrigation water waste. These parameters were evaluated by conducting three experiments using a drought-tolerant maize hybrid and a non-drought-tolerant (‘standard’) maize hybrid receiving 50, 100, and 150% of the recommended optimal nitrogen (N) fertilizer rate and grown under well-watered conditions, drought stress from the 14 leaf collar maize phenological stage (V14) to maize physiological maturity (R6), and drought stress from the blister maize phenological stage (R2) to R6. Across hybrids, ET_a decreased with increased duration of drought stress. The drought-tolerant hybrid had 7 and 8% greater CWP and IWP, respectively, compared to the standard hybrid when drought stress began at V14. Mid-season K_ab was 1.08, 0.89, and 0.73 under well-watered conditions and when drought stress began at R2 and V14, respectively. These results reveal that (i) maize achieved more effective physiological acclimation with earlier exposure to drought stress, (ii) grain yield of the drought-tolerant hybrid was unchanged by earlier, compared to later, onset of drought despite a 10% decrease in ET_a, and (iii) two phases of acclimation were identified: Maize K_ab declined upon exposure to drought but stabilized as the crop acclimated.

中文翻译：

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玉米对持续中度干旱胁迫的响应揭示了改善管理的线索

作物水生产率（CWP），灌溉水生产率（IWP），实际季节基础作物系数（K _ab）和实际作物蒸散量（ET _a）是准确估算作物需水量以防止灌溉水浪费的基本参数。通过使用耐旱的玉米杂交种和非耐旱的（“标准”）玉米杂交种进行三个实验，评估了这些参数，该杂交种分别获得建议的最佳氮肥施用量的50％，100％和150％，并在水分充足的条件下，干旱胁迫从14个叶领玉米的物候期（V14）到玉米生理成熟期（R6），干旱胁迫从起泡的玉米物候期（R2）到R6。跨杂种，ET _a随着干旱胁迫持续时间的增加而减少。与V14干旱开始时的标准杂种相比，耐旱杂种的CWP和IWP分别高7％和8％。在浇水条件良好以及R2和V14分别开始干旱胁迫的季节中，_Kab分别为1.08、0.89和0.73。这些结果表明，（i）玉米在更早暴露于干旱胁迫下获得了更有效的生理适应性；（ii）与干旱相比，耐旱杂种的籽粒产量与早期相比没有变化，尽管ET降低了10％。_a和（iii）确定了两个适应阶段：玉米K _ab在暴露于干旱时下降，但随着作物适应而稳定。