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U of I Study Shows Cover Crops Could Cut Nitrogen In Illinois Drainage Water By 30%
Original source: University of Illinois
U of I study shows cover crops could cut nitrogen in Illinois drainage water by 30%
New University of Illinois research shows widespread seeding of cereal rye as a winter cover crop could reduce nitrate levels in Illinois tile drainage by 30%. The simulation study report was published in “Science of the Total Environment.”
The U of I research team, part of the College of Agricultural, Consumer and Environmental Sciences (ACES) and The Grainger College of Engineering, knew from small-scale studies that cover crops take up nitrate from soil water with long-lasting effects throughout the growing season. The team’s new study is the first to estimate cereal rye’s potential on a statewide level.
The study simulated both cover crop seeding and no seeding and either fall or spring fertilizer applications under actual climatic conditions in Illinois between 2001 and 2020. They used a crop simulation model known as Decision Support System for Agrotechnology Transfer, which allows multi-year growth projections for more than 42 crops. While cereal rye wasn’t one of the crops, the researchers adapted the model’s parameters for winter wheat, which was the most similar in the model.
The study co-author, Rabin Bhattarai, associate professor in the Department of Agricultural and Biological Engineering, highlighted two implications. “One is that farmers should apply a winter cover crop, such as cereal rye, to reduce tile water flow and nitrate loss by 25% and 30%, respectively,” Bhattarai said. “Our data also reinforced that farmers should switch to spring fertilization, if possible. We compared spring versus fall fertilization with and without the cover crop, and fall was worse for nitrate loss in both scenarios.”
The model also simulated cover crop effects on corn and soybean yields and found, overall, that cereal rye had a slightly positive impact on corn and soybean under both fertilization schedules. Although there were some variations among years and locations, over the 20-year simulation, there was no evidence of a yield penalty, Bhattarai noted.
“We wanted to explore the benefits on the whole-state level to show what could happen if thousands of farmers adopted this conservation practice simultaneously,” he said. “The water quality benefits would be significant.”
Bhattarai’s model struggled a little in the hillier, southern section of Illinois. But when compared with real-world corn and soybean yields, the yields forecast by the model were a close match, suggesting the model was likely accurate overall.
The project’s early phase began with small-scale field experiments to understand cover crop and fertilizer timing on nitrate loss in tile and runoff water. These experiments were used to develop the modified model. They also supported an online decision-support tool, funded by the Illinois Nutrient Research and Education Council, for farmers considering cover crops. Farmdoc published a full article on the tool.
“Using our dashboard, farmers can get simulated results of cereal rye growing as a cover crop in their actual fields,” said study co-author, Jonathan Coppess, ACES associate professor in the Department of Agricultural and Consumer Economics.
“At different dates within a two-week window of expected planting for the cash crop, farmers can compare potential biomass in the field, carbon-nitrogen ratio in that biomass, nitrogen uptake and nitrogen loss reduction,” Coppess continued.
“To improve results further, farmers can provide more specific information for their fields, including cropping history and management programs.”
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