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| 基于高频监测的稻麦轮作区水稻泡田期排水与硝态氮输出特征 |
| Patterns of nitrate nitrogen losses through drainage during the puddling period in rice-wheat rotation areas under high-frequency monitoring |
| 投稿时间：2024-11-22 修订日期：2025-03-09 |
| DOI： |
| 中文关键词: 稻麦轮作农田 氮素 泡田期 重复子采样 稻田排水 |
| 英文关键词: Rice-wheat rotation field, nitrogen, puddling period, subsampling, drainage from paddy fields. |
| 基金项目:国家自然科学基金项目（面上项目，重点项目，重大项目）;扬州市”绿扬金凤计划” |
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| 中文摘要: |
| 水稻泡田期是稻麦轮作区农田旱转水的变化时段，在大量灌溉水抬升农田地下水位的同时，麦作期残留在土壤中的硝态氮迅速溶于水；除了发生一系列生化反应，这些硝态氮可能随稻田排水进入受纳水体，成为区域水环境污染源。鉴于常规水文水质监测难以捕捉短期内排水中硝态氮变化的详细过程，本文采用高频原位监测与重复子采样方法，分析了泡田期稻田排水与硝态氮流失特征以及水质采样频率对氮素输出负荷的影响。监测结果显示，研究区稻麦轮作农田开敞的排水沟导致泡田期排水量偏大，排灌比高达32.3%；排水硝态氮总输出负荷为1.11 kg N ha-1，其中首日流失负荷占泡田期硝态氮总流失量的81.1%，表现出明显的初期冲刷现象；这说明农田土壤中残余的硝态氮在泡田期通过强烈的反硝化作用及稻田排水过程而流失。数据分析结果表明，要有效识别泡田期硝态氮流失的初期冲刷现象，排水水文与水质监测的采样间隔需缩短至2~8小时。研究建议，水稻泡田期采取控制排水或尾水回用等措施来降低稻田水肥流失梯度，提高水肥利用效率。 |
| 英文摘要: |
| In rice-wheat cropping systems, the puddling period is a critical transition phase between dry and wet conditions. During this period, as the water table is rapidly elevated through irrigation, the nitrate nitrogen accumulated during the previous winter wheat season tends to be flushed out by agricultural drainage into receiving water bodies, which becomes a potential cause for impaired water bodies. Since traditional grab sampling methods struggle to capture the rapid hydro-biochemical changes that occur during this phase, we deployed a high-frequency, in-situ monitoring system and conducted subsampling analysis during the puddling period to elucidate the patterns of drainage discharge and nitrate losses and to investigate the impacts of sampling frequencies on the estimation of nitrate losses. Our findings revealed that over a three-day puddling period, the total agricultural drainage is relatively high, with a drainage-to-irrigation ratio of 32.3%. Moreover, of the total nitrate losses amounting to 1.11 kg N ha-1, a staggering 81.1% occurred on the first day, underscoring a pronounced first flush effect. This phenomenon may be caused by the interactions between nitrates accumulation in the upper soil layers during the previous winter wheat cultivation and the subsequent nitrate removal processes, such as denitrification. Our further resampling analysis indicated that, to effectively capture the first flush effect, the optimal sampling interval should be limited to 2 to 8 hours. Considering the substantial volume of drainage water and its significant impact on nitrate loss, it is recommended to implement conservation practices like controlled drainage or drainage water recycling. These strategies can help lower the risk of over-drainage and thus enhance the use efficiency of irrigation water and nitrogen. |
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