中文摘要：

灌区地下水位调控可增加作物对浅层地下水的利用量，但当地下水含盐量较高时，作物对其利用会加快盐分在根区的累积速度，进而影响灌溉淋洗制度。本文根据农田水盐平衡的基本原理，考虑不同埋深的浅层地下水利用条件下根区土壤盐分的累积过程，建立了土壤盐分淋洗周期的理论模型，并根据两组试验数据进行了应用分析。计算结果显示，位于半干旱区的研究区，地下水含盐量4.43 g/L，埋深维持在1 m和1.5 m时，多年平均降雨条件下，棉花生长期内需要排水洗盐的周期分别为100 d 和140 d；埋深大于2 m 时，淋洗周期超过了生长期。另一研究区位于干旱区，滴灌棉田地下水埋深为1.5 m时，用含盐量为2.81 g/L的微咸水进行滴灌，棉花生长期内需要排水淋洗的时间为78 d左右。因此，即使在灌区水位调控抬高地下水位后，在一个生长周期内，根区土壤盐分的增长过程仍然相对缓慢，为灌区制定淋洗制度提供了时间窗口。

英文摘要：

Water table management in irrigated areas may increase shallow groundwater use by crops. But the high salt content of groundwater results in faster buildup of salinity in crop root zone,which in turn af-fects leaching schedule of the irrigation districts. Based on general salt and water balance in crop fields in irrigated areas, a simplified model was proposed in this paper to calculate leaching cycle for crops that use shallow groundwater at different water table depth, considering the salt accumulation process in root zone of crops. Subsequently, leaching cycles were calculated for two study sites with soil salinity measure-ments. For the case study in a semi-arid irrigation area,under the current irrigation scheduling and the av-erage rainfall condition, the calculated leaching cycle for cotton fields is 100 days for water table depth at 1 m and 140 days for water table depth at 1.5 m with the groundwater salinity maintained at 4.43 g/L;when the water table depth is greater than 2 m, the calculated leaching cycle is longer than the growing period. In another case study in an arid irrigation area with saline groundwater buried at 1.5 m deep, the calculated leaching cycle for plastic mulched and drip irrigated cotton is 78 days, applying slightly saline irrigation water with salinity of 2.81 g/L. These results indicate that managing water table depth under con-trolled drainage practice may increase crop use of shallow groundwater that contains dissolved salts, the rate of salinity buildup, however, is relatively slow, leaving a time window for making proper leaching schedule. The results from this study provide theoretical reference for salinity management in irrigated agri-cultural regions that adopt controlled drainage technique.