水位调控下水稻-小麦轮作系统氮素化学行为特征及其调控机制研究

Water level control is the key technique to realize the united regulation of irrigation-drainage in farmland, which plays an important role in improving the ecological environment of farmland. As the existing research is insufficient to show the rules of nitrogen loss influenced by water level regulation, by taking rice-wheat rotation system of southern area as the research object and field water level control as the research carrier, the detail research on the key scientific problems of transformation mechanism of nitrogen chemical behavior characteristic, as well as water level regulation strategy, will be carried out by lysimeter, soil column tests, laboratory physical and chemical analysis, model simulation and further plot verification tests. .Through the quantitative research of different fertilizer nitrogen loss pathways, the research will study nitrogen fertilizer effects on ecological environment, clarify the migration law of nitrogen in water and soil environment, and reveal the variation of nitrogen in response to different water level control. In addition, relative soil, crop and meteorological factors of paddy fields under water level control will be monitored. The effect of relative soil, crop and meteorological factors under water level control will be quantitative analyzed. Based on the quantitative analysis above, the main influence factors of nitrogen element changes on different water level control will be determined and discussed. Considering the interaction crop growth, nitrogen transport and water movement, migration and transformation model of nitrogen will be constructed under water level control. Moreover, the new migration and transformation model of nitrogen will be used to evaluate the nitrogen loss for various farmland water level schemes, water level suitable indicators will be optimized and the high efficiency water level regulation mechanism of irrigation-drainage will be established. .The research results will have important theoretical meaning and application value. It will be helpful for establishing the evaluation system of water level regulation in rice-wheat rotation system of southern area, optimizing irrigation-drainage management strategies in irrigated area and controlling agricultural non-point source pollution.

水位调控是实现灌排联合调控的关键技术，在改善农田生态环境方面发挥重要作用，但目前水位调控对农田氮素流失影响研究甚少。本项目以南方水稻-小麦轮作系统作为研究对象，以水位调控作为研究载体，通过测坑、土柱试验、理化分析、模型模拟、小区验证对农田氮素化学行为特征、机理及调控机制等关键科学问题进行研究。.通过肥料氮不同损失途径的定量研究，研究肥料氮的生态环境效应，阐明氮素在水体、土壤中迁移转化规律，揭示氮素变化特征对不同水位调控的响应规律；量化土壤、作物及气象参数对农田氮素变化的影响，找到农田氮素变化的主控因子；构建水位调控下作物生长-氮素迁移转化-水分运动的氮素模型；对不同农田水位情景氮素流失进行评价，优化水位适宜指标，建立田间高效灌排水位调控机制。.研究成果对构建南方稻麦轮作区水位调控评价体系，优化灌区灌溉排水管理策略，及控制农田面源污染具有重要的理论意义和应用价值。

目前以土壤含水率作为灌排控制指标，空间变异性较大，不易准确掌握。因此，如何以农田水位调控技术作为水稻-小麦轮作系统（地表-地下协同调控）高效灌排技术指标体系急待深入研究。本项目主要研究结论如下：.（1）氮素淋失量取决于降水（或灌水）和氮素浓度两个因子，节水灌溉水位调控对对肥料氮淋失的抑制效果、氨挥发总量显著小于常规灌溉，氮素植株吸氮量、土壤总氮含量高于常规灌溉。.（2）水位调控对耗水量、渗漏水量和蒸散量的影响最大，本项目不同水位调控对耗水量、渗漏水量和蒸散量的影响不显著。氮素地表水和地下水的主要污染源，磷所占比例较低，节水灌溉水位调控模式地表、地下流失TN、NO3--N、NH4+-N和COD显著低于常规灌溉。.（3）麦田受淹有利于地下水NH4+-N、NO3--N浓度的降低，受淹处理地下水氮素浓度均小于相同排水强度的没有受淹的处理。随着淹水时间延长，氮素浓度降低速度缓慢。麦田地下水NH4+-N流失则可以用对数函数进行预测预测模拟。.（4）以冬小麦为例，建立了考土壤含水量修正后的水位——产量响应模型，模型精度更高，可以更加准确的反映水位与产量的关系。.（5）水位调控技术在我国南方稻麦轮作区实际应用时，比较合理的田间排水系统工程布局为：在格田出口处安装自动控制排水装置，有效控制稻田水层；在农沟出口处设置农沟控制排水闸门，达到控制田间渗漏量的目的；当麦田对地下水的降落速度要求比较慢时，农沟可以调蓄一定水深，即可满足水位控制要求。.（6）在综合评价种植产量、水分利用效率及氮磷排放量等各项指标的情况下，水稻小麦轮作系统以水旱轮作水位调控——稻田间歇灌溉+麦田地下水位（-200/3d）调控最有利于水稻/小麦轮作系统综合效益的发挥。