基于淋洗需求的棉田微咸水滴灌-洗盐方案研究

Brackish drip irrigation is increasingly used in arid-semiarid area. And the secondary salinization problem resulted by it is gradually observed. Leaching soil accumulated salt is important to guarantee that soil salt in root zone is lower than crop salt tolerance for avoiding crop failure and farmland abandoned. Some research work has showed that local leaching was considerable when drip irrigation was used to leach soil salt. Leaching requirement is a key indicator for soil salt leaching. Therefore, based on leaching requirement, researching the leaching method, time, water quantity and quality for soil accumulated salt leaching is urgent and necessary. So, in this project, that soil salt leaching under brackish drip irrigation will be researched with methods including field investigation, experiment, dyeing tracer, soil water-solute numerical simulation and so on. The main research contents include: analyzing drip irrigation wetting patterns and soil salt transport and accumulation characters to ascertain soil water-salt distribution functions; studying the effect of soil water-salt transport on Leaching Fraction to derive leaching Requirement computational formula for brackish drip irrigation; establishing brackish drip irrigation-Leaching schemes in cotton field based on Leaching Requirement. The results will supply the theoretical foundation for effectively using brackish drip irrigation, preventing soil secondary salinization and farmland environment sustainable. Research achievements have broad applying prospects in many fields such as irrigation and water conservation, hydrogeology, hydraulic science, environment science.

微咸水滴灌越来越多地在干旱半干旱地区应用，其引发的次生盐渍化问题也逐渐突显。为了保障根区土壤盐分不超过作物耐盐阈值造成作物减产或农田废弃，土壤累积盐分的淋洗尤为重要。已有研究表明，采用滴灌淋洗土壤盐分时局部淋洗是可观的。土壤盐分淋洗中淋洗需求是关键指标，因此，基于淋洗需求研究微咸水滴灌土壤累积盐分淋洗方式、时间及水质水量配置是亟需的。本项目拟结合室内土槽实验、染色示踪、野外实验和土壤水溶质数值模拟等方法开展微咸水滴灌土壤累积盐分淋洗的研究；分析微咸水滴灌湿润体扩展规律和盐分迁移积聚特征，探求土壤水盐分布函数；研究土壤水盐运移对微咸水滴灌淋洗分数的影响，推求淋洗需求计算公式；基于淋洗需求，建立适宜的棉田微咸水滴灌-洗盐方案；为干旱半干旱地区有效利用微咸水滴灌、防止土壤次生盐渍化和农田环境可持续提供理论依据。研究成果在农田水利、水文地质、水利科学以及环境科学等诸多领域具有广泛的应用前景。

微咸水滴灌越来越多地在干旱半干旱地区应用，其引发的次生盐渍化问题也逐渐突显。为了保障根区土壤盐分不超过作物耐盐阈值造成作物减产或农田废弃，土壤累积盐分的淋洗尤为重要。已有研究表明，采用滴灌淋洗土壤盐分时局部淋洗是可观的。因此，为了干旱绿洲农田生态可持续，本项目在室内开展了土槽滴灌水盐运移实验、田间微咸水膜下滴灌-洗盐实验，并建立了微咸水膜下滴灌三维土壤水盐运移数值模型，探讨微咸水膜下滴灌-洗盐方案。研究结果表明：（1）当灌溉水总溶解固体（TDS）为1.61-3.21 g/L时，微咸水膜下滴灌棉花淋洗需求（LR）推荐最佳范围为0.05-0.15，根据水资源情况，实际应用中，适当取较小值。（2）当淋洗分数（LF）小于0.2时，根区土壤电导率值随着灌水量的增加而减小，而当LF大于0.2时，土壤电导率值则随着灌水量的增加而增加。（3）概化田间膜下滴灌为线源入渗推求获得土壤水分运移二维方程解析解。（4）建立了微咸水膜下滴灌棉花三维数值模拟模型。（5）推荐膜下滴灌-淋洗方案为：每年播种前进行一次漫灌淡水淋洗，水量为57.3mm；播后苗期淡水滴灌，水量33.0mm，其他时期采用微咸水；前后期灌水间隔为5天，在花铃盛期为3天。