Assessing winter cover crop nutrient uptake efficiency using a water quality simulation model
Assessing winter cover crop nutrient uptake efficiency using a water quality simulation model
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使用水质模拟模型评估冬季覆盖作物养分吸收效率
DOI：
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发表时间：
2013
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通讯作者：
M. Lang
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作者：
I. Yeo;Sangchul Lee;A. Sadeghi;P. Beeson;W. Hively;G. McCarty;M. Lang
冬季覆盖作物是一种有效的保护管理措施，具有改善水质的潜力。整个切萨皮克湾流域（CBW）位于美国大西洋中部，冬季覆盖作物的使用一直受到重视，联邦和州的成本分担计划可用于农民补贴覆盖作物的建立成本。本研究的目的是评估在流域尺度（~ 50 km2）种植冬季覆盖作物对改善水质的长期效果，并确定高硝酸盐出口的关键源区。利用水质监测数据，对一个基于物理的流域模拟模型——水土评估工具（SWAT）进行了校准和验证，以模拟1990-2000年期间的水文过程和农业养分循环。为了准确模拟冬季覆盖作物生物量与生长条件的关系，研究人员开发了一种新的方法，利用基于多时段卫星测量的物种特异性冬季覆盖作物性能，进一步校准控制叶面积发育曲线的植物生长参数。开发了多个SWAT情景，以获取无冬季覆盖作物情况下硝酸盐负荷的基线信息，并调查硝酸盐负荷在不同冬季覆盖作物种植情景下的变化情况，包括不同的物种、种植日期和实施区域。模拟结果表明，冬季覆盖作物对水分收支的影响可以忽略不计，但显著减少了硝酸盐向地下水的淋滤和向水道的输送。在没有冬季覆盖作物的情况下，农田年硝酸盐负荷约为14 kg ha - 1，但在有覆盖作物的情况下，农田年硝酸盐负荷降至4.6-10.1 kg ha - 1，减少率为27-67%。黑麦是最有效的品种，在田间早期种植可以减少高达93%的硝酸盐淋失。覆盖作物的早期种植（约30天的额外生长期）是至关重要的，因为与后期种植情景相比，它使硝酸盐出口量额外减少了约2公斤/公顷。覆盖作物的有效性随着覆盖范围的增加而增加。土壤排水良好的农田和那些经常用于种植玉米的农田具有更高的硝酸盐淋滤和出口到水道的潜力。本研究支持有效实施覆盖作物计划，部分是通过帮助确定实施覆盖作物计划的关键污染源区域。
Winter cover crops are an effective conservation management practice with potential to improve water quality. Throughout the Chesapeake Bay watershed (CBW), which is located in the mid-Atlantic US, winter cover crop use has been emphasized, and federal and state cost-share programs are available to farmers to subsidize the cost of cover crop establishment. The objective of this study was to assess the long-term effect of planting winter cover crops to improve water quality at the watershed scale (~ 50 km 2 ) and to identify critical source areas of high nitrate export. A physically based watershed simulation model, Soil and Water Assessment Tool (SWAT), was calibrated and validated using water quality monitoring data to simulate hydrological processes and agricultural nutrient cycling over the period of 1990–2000. To accurately simulate winter cover crop biomass in relation to growing conditions, a new approach was developed to further calibrate plant growth parameters that control the leaf area development curve using multitemporal satellite-based measurements of species-specific winter cover crop performance. Multiple SWAT scenarios were developed to obtain baseline information on nitrate loading without winter cover crops and to investigate how nitrate loading could change under different winter cover crop planting scenarios, including different species, planting dates, and implementation areas. The simulation results indicate that winter cover crops have a negligible impact on the water budget but significantly reduce nitrate leaching to groundwater and delivery to the waterways. Without winter cover crops, annual nitrate loading from agricultural lands was approximately 14 kg ha −1 , but decreased to 4.6–10.1 kg ha −1 with cover crops resulting in a reduction rate of 27–67% at the watershed scale. Rye was the most effective species, with a potential to reduce nitrate leaching by up to 93% with early planting at the field scale. Early planting of cover crops (~ 30 days of additional growing days) was crucial, as it lowered nitrate export by an additional ~ 2 kg ha −1 when compared to late planting scenarios. The effectiveness of cover cropping increased with increasing extent of cover crop implementation. Agricultural fields with well-drained soils and those that were more frequently used to grow corn had a higher potential for nitrate leaching and export to the waterways. This study supports the effective implementation of cover crop programs, in part by helping to target critical pollution source areas for cover crop implementation.