Intensive long-term monitoring combined with modeling indicates the potential of cover crops to reduce nutrient export at watershed scales
Abstract
Management of agroecosystems has widespread consequences for food security, environmental quality, and sustainability. Meeting intended targets for water quality in the Mississippi River Basin will require changes in farm management practices, yet traditional best-management practices are not effective in tile-drained watersheds. Small-scale plot and field studies have illustrated how alternative management practices such as the addition of cover crops can improve water quality from tile drains. Whether these findings scale up to the watershed scale is not known. We explored the extent to which the addition of cover crops could improve water quality in a watershed in central Illinois. We conducted intensive monitoring of water quality from two multi-field (approx. 1000 acre) watersheds from 2016 to present. Farmers maintained their own management practices, and we aerially applied cover crops as radish, oats, cereal rye and/or annual rye in the treatment watershed. We found that after two years, the cover cropped watershed had substantial reductions in nitrogen loss and improvements in water quality. A physically-based watershed model, the Soil and Water Assessment Tool (SWAT), was applied to simulate hydrological processes and agricultural nutrient cycling and quantify the environmental benefits of cover crops. Spatial data (e.g., crop use, soil, and DEM), meteorological data, and nearly four years (2015-2018) of detailed observed flow and water quality data were used to calibrate and validate the model. Multiple model scenarios were developed to assess the effect of cover crops on nitrate loading. Simulation results showed significant differences in watershed yield, tile flow, nitrate load, and nitrogen uptake between scenarios of no cover crops to 100% cover cropping of the watershed. An economic model underscores the complex nature of using cover crops. Given that we only cover cropped 60% of the watershed yet found a large improvement in water quality, our findings indicate that cover crops might be highly effective for meeting water quality targets in the Upper Mississippi River Basin.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGC31J1351O
- Keywords:
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- 0402 Agricultural systems;
- BIOGEOSCIENCES;
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 1630 Impacts of global change;
- GLOBAL CHANGE;
- 1803 Anthropogenic effects;
- HYDROLOGY