Research on regulation of Soil water movement of drip irrigation under mulch in oasis cotton

本论文的野外实验是在中国科学院阿克苏水平衡试验站完成。通过对棉花整个生长期内土壤水分进行连续取样，对不同灌溉定额情况下的绿洲棉田水分运动进行研究，阐明不同灌溉定额条件下绿洲棉田的水分变化规律，为提高水分的利用效率提供科学依据，为农业生产提供一定的指导。通过研究得到以下结论： 1.利用HYDRUS-2D数值模型对膜下滴灌方式下土壤水分运动进行数值模拟，可以较好的模拟土壤水分的分布特征，并能够反映出土壤质地和灌水量的敏感程度，对干旱区农业生产有一定的技术参考价值。 2.由于30-40cm粘土层的存在，使土壤水分运动具有特殊的形式，0-30cm为变化明显区，主要为棉花蒸腾和棵间蒸发所消耗，并且受到地下水的影响较小；40-80cm土壤水分没有明显的变化，与地下水关系比较紧密。为在制定灌溉制度时确定计划深度提供理论依据。 3.由于30-40cm粘土层的存在使土壤水运动以及土壤剖面含水率分布状况具有独特的形式。对棉花根系生长及空间分布产生很大影响，使根系的垂直分布呈倒金字塔形；灌水时对土壤水的下渗有很大的滞缓作用，并使根系生长受阻，导致根系主要集中在土壤剖面0-30cm。 4.由于干旱区水资源严重短缺，按经济效益最佳的灌溉定额进行节水灌溉，可有效地提高棉花的水分利用效率。在此基础上将有限水资源首先分配在棉花的需水临界期（花铃期和蕾期）会进一步提高水分利用效率。棉花水分利用效率是衡量棉花用水效率的指标之一，要获得最好的社会经济效益，必须兼顾产量与水分利用效率。根据实测资料膜下滴灌条件下绿洲棉田棉花水分利用效率为0.47kg/m3-0.63kg/m3，水分利用效率还有一定的提升空间。This experimental study is conducted at Aksu Water Balance Experimental Station. Soil samples are sampled in the cotton field during cotton growth period for analyzing soil moisture every 7 days. It is described that soil moisture in arid land cotton field under different irrigation quota. The purpose of this study is to provide the decision-making evidence for establishing new water-saving irrigation practice, which can maintain water-salt balance in cotton field, for controlling salinity in irrigated agriculture land. The main conclusions were as follows: Based on the theory of unsaturated dynamic，a two-dimensional vertical plane model was developed to numerical simulate soil water movement of drip irrigation under mulch by Hydrus-2D.The soil water movement of stratified soil in the experimental plot was calculated in the condition of drip irrigation under mulch. The field test was carried out in Aksu water balance experiment station. Verifying the numerical simulation results with both under and between mulch the water content of soil profile in different test field with different irrigation treatment, it indicated that they have better conformity. Besides, Comparing the soil water content of 0cm-10cm deep in different time and different location observed by PTM-48(Photosynthesis Transpiration Monitor) with numerical simulation results, we can see that the numerical simulation results less than value of field test, but the changing tendency was agreeable. So the numerical simulation model of soil water movement in the condition of drip irrigation under mulch is acceptable. From the result of experiment we can learn, first, it is well numerical simulation model to simulate water movement in drip irrigation under mulch; second, because of the clay stratification in 30cm-40cm the soil movement has explicit difference. The obvious difference can be seen from 0cm-30cm of soil profile, but there no sharp change below the 40cm. ,while the normalized root density distribution with soil profile performance take on inverted pyramid.Because the arid area water resources is serious short, take the best economic efficiency irrigation quota to water-saving irrigation can effectively enhances the moisture content use efficiency of the cotton.According to actual measurement of the cotton drip irrigation under mulched ,the water use efficiency is 0.47kg/m3-0.63kg/m3, there is large uprating capacity the water use efficiency