泡田期稻田养分流失特征与回用效果分析

Nutrients loss and their recovery during flooding periods in paddy fields

[目的]揭示太湖地区泡田期田-沟-河灌排系统稻田养分流失特征及其在尾水回用下养分拦截回用比例及效果。[方法]基于原位试验记录各级灌排单元中的水量、水质,分析泡田期稻田养分流失特征,选用熵权法计算各指标权重,识别各级灌排单元的关键水质因子,并结合水量、水质数据计算尾水回用格局下各水质因子的回用率。[结果]泡田期内各指标浓度在田-沟级呈先升高后降低的趋势,而河道级延后1~2 d后升高,泡田结束时均高于初始水平,各水质指标浓度随水流流向呈梯级递减趋势。田-沟级关键水质因子为氮,随水流至河道级后转变为化学需氧量(COD)。在尾水回用格局下,总回用水量达到泡田定额的45.56%,总氮(TN)、铵态氮(NH_(4)^(+)-N)、总磷(TP)、COD回用率分别达到51.96%、33.68%、57.61%、42.65%。[结论]泡田期灌溉定额大,稻田养分流失风险高,通过尾水回用可有效减少泡田定额,并将稻田排水中的养分回归入田以降低污染物外排风险。本研究有助于从灌排单元尺度上提高节水、减排水平,助力太湖地区农业可持续发展。

【Objective】Flooding in paddy fields facilitates weed control,improves phosphorus availability,and aids in pest management.This paper experimentally studies leaching and recovery of nutrients during flooding period in paddy fields in the Tai Lake Basin.【Method】The experiment was conducted in a paddy field with well-established field and main drainage ditches.During the experiment,we measured the quantity and quality of water in each irrigation-drainage unit in both field and main drainage ditches.The significance of each nutrient was calculated using the entropy weight method to identify key water quality factors in each irrigation-drainage unit.The data measured in both field and main drainage ditches were used to calculate the recovery of the leached nutrients and their reuse.【Result】After the inception of the flooding,the concentrations of all nutrients measured in the ditches increased initially followed by a decline.In the main drainage ditches,it took one to two days for changes in the nutrient concentrations to emerge.At the end of the flooding,the concentrations of nutrients in all ditches were higher than those before the flooding;they decreased as water flow increased.The analysis of the entropy weight method showed that nitrogen was the key water quality factor in the field ditches,while COD was the key water quality factor in the main ditches.Our results showed that 45.56% of drained water was reused for irrigation,and the recovery rates of TN,NH_(4)^(+)-N,TP and COD were 51.96%,33.68%,57.61%and 42.65%,respectively.【Conclusion】The large irrigation volume used during the flooding period in the paddy fields increased the risk of nutrients leaching.Reusing the drained water is an effective strategy to minimize nutrients losses and reduce environmental pollution.Improving water conservation and reducing greenhouse emissions in each irrigation-drainage unit are crucial for developing sustainable agriculture in the Taihu Lake Basin.