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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。
The regulation of groundwater level in irrigated area can increase the utilization of crops for shallow groundwater. However, when the salinity of the local groundwater is high, the utilization of crops will speed up the accumulation of salt in the root zone, which will affect the irrigation and leaching system. According to the basic principle of farmland water and salt balance, a theoretical model of soil salt rinse cycle was established considering the process of soil salinity accumulation in the root zone under the conditions of shallow groundwater utilization at different burial depths. Based on the two sets of experimental data, the application analysis . The results show that in the study area located in the semi-arid area, the salinity of groundwater is 4.43 g / L and the depth is maintained at 1 m and 1.5 m. Under the average rainfall condition for many years, 100 d and 140 d. When the burial depth is more than 2 m, the leaching period exceeds the growth period. The other study area is located in the arid area. When the groundwater depth of the drip irrigation cotton field is 1.5 m, drip irrigation with brackish water containing salt content of 2.81 g / L, the time required for drainage and washing in the cotton growing period is about 78 days. Therefore, the growth of soil salinity in the root zone is still relatively slow during one growth cycle even after water level regulation in the irrigation area elevates the groundwater level, providing a time window for setting up the leaching system in the irrigation area.