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由于其节水增产的优势,近年来,膜下滴灌在我国西北干旱区绿洲农田得到了迅速推广。由于轮灌仍是目前农田用水分配的主要方式,并且还需要考虑滴灌产生的土壤盐分积累问题,因此,对滴灌灌水量(Q)、灌水周期(T)以及相应的深层下渗(L)关系研究,不仅是农田用水分配的要求,也是盐分控制的需要。本文利用田间试验数据校验HYDRUS-2D模型,进行数值模拟试验,并结合马尔可夫链模型分析,分析不确定蒸散下的Q-T-L关系,结果显示:①总体上,随着灌水量的增加,可支持的灌溉周期增加,同时深层下渗增加,Q-T-L关系曲线表现为非线性关系;②其中存在3个关键Q-T阈值点:深层下渗出现点(Q为35mm,T为5d)、灌溉周期增加减缓点(Q为65mm,T为10d)、最大灌溉周期点(T为11d,Q为120mm)。因此,①在以水分利用为优先的模式下,最大灌水量不应超出35mm,最大灌溉周期为5d;②在灌溉间隔时间优先的模式下,有最大灌水周期11d,所需灌水量为120mm,适宜的灌水周期为10d,所需灌水量为65mm;③在有盐分淋洗需求模式下,适宜的灌水周期为10d,所需灌水量为65mm,产生下渗量约占灌水量17%,可用于根区盐分淋洗;④潜水位对灌溉产生作用的阈值深度是-300cm,高于时潜水可以补给根区土壤水分,从而增加灌溉周期。利用本文数值模拟与方法,可以为不同气候与土壤情形区域农田滴灌灌溉设计提供指导。
Due to its advantages of water saving and yield increase, in recent years, drip irrigation under the film has rapidly been promoted in the oasis farmland in the arid region of northwestern China. Because rotation irrigation is still the main way of water allocation in farmland and the accumulation of soil salinity due to drip irrigation needs to be considered, the relationship between drip irrigation (Q), irrigation cycle (T) and corresponding deep infiltration (L) Research is not only a requirement of farmland water allocation, but also a requirement of salt control. In this paper, the HYDRUS-2D model was calibrated with field test data, and numerical simulation experiments were carried out. Combining with Markov chain model analysis, the relationship of QTL under uncertainty of evapotranspiration was analyzed. The results showed that: (1) Generally, with the increase of irrigation amount, Supported irrigation cycles increased while deeper infiltration increased, the QTL curve showed a nonlinear relationship; ② There were three key QT threshold points: deep infiltration point (Q = 35mm, T = 5d), irrigation cycle increased slowed down Point (Q is 65mm, T is 10d), maximum irrigation period (T is 11d, Q is 120mm). Therefore, ① In the mode of using water as priority, the maximum irrigation amount should not exceed 35mm and the maximum irrigation period is 5d; ② In the irrigation priority mode, there is the maximum irrigation cycle 11d, the required irrigation amount is 120mm, The suitable irrigation period is 10 days, and the required irrigation amount is 65mm. In the mode of demand of salt leaching, the suitable irrigation cycle is 10 days, the required irrigation amount is 65mm, the infiltration rate is about 17% of the irrigation amount, In the root zone salt leaching; The diving depth of the role of irrigation threshold depth is -300cm, when it is higher than when the submerged root can supply soil moisture, thereby increasing the irrigation cycle. Using the numerical simulation and the method in this paper, we can provide guidance for drip irrigation design of agricultural fields in different climate and soil conditions.