New model analyzes weather conditions before planting for better fertilizer applications


As nitrogen fertilizer costs and environmental concerns rise, informed decisions about fertilizer rates are more important than ever. The latest modeling effort from the University of Illinois examines the role of pre-growing season weather on soil nitrogen dynamics and late-season corn yield.

The new study, “Evaluating the Impacts of Pre-Growing Season Weather on Soil Nitrogen Dynamics and Corn Productivity in the U.S. Midwest,” was published in Field Crops Research.

“When farmers plant maize in spring, they already know what happened during the pre-growing season, from the previous autumn to spring,” said Ziyi Li, a doctoral student at the University of the Island. and lead author of the new study, in a news story. Release. “Unlike the upcoming growing season, which we cannot reliably predict, we can use pre-growing season information to guide farmers in adjusting their fertilizer application.”

Li used an advanced agroecosystem model known as an ecosystem to understand the correlation between temperature and precipitation during the pre-growing season with soil inorganic nitrogen content and yield.

“The ecosys model has been widely used in many different cases for agriculture, and this study further demonstrates that ecosys can work well in simulating nitrogen cycles,” said Kaiyu Guan, associate professor at the U of I and the study’s principal investigator, in a press release. “The validation dataset we used comes from decades of nitrogen testing conducted by our collaborators in Illinois and other Midwestern states. We found that the model can actually reproduce these models, not just the Illinois data, but also the broader Midwest models.

Li’s model revealed increased nitrogen leaching during wetter pre-growth seasons, resulting in a 5-14% yield reduction when no spring fertilizer was applied. Even when 150 pounds of nitrogen per acre was applied, Illinois’ 2018 yield dropped 1-3% due to heavy preseason rainfall.

“In our analysis, we found that applying more fertilizer can mitigate and even eliminate the yield loss induced by excessive rainfall before the growing season,” Li said. “Based on our model, If an Illinois farmer applies 150 pounds of nitrogen per acre, the 1-3% yield loss can be avoided by adding about 16 pounds of additional nitrogen.”

Reduced soil microbial activity and improved leaching also reduced soil inorganic nitrogen during cooler than normal pre-growing seasons.

“The effects of cold temperatures before the growing season on yield cannot be eliminated by adding additional fertilizer,” Li said. “This is because temperature not only affects soil nitrogen content, but also appears to limit early growth in a way that affects yield potential, even if the weather returns to normal later.”

Li said the model could improve current nitrogen use calculators. In the meantime, farmers looking to fine-tune fertilizer use can consider strip trials, said Emerson Nafziger, professor emeritus at the U of I.

“High nitrogen levels tend to produce dark green corn, but lower levels might as well,” Nafziger said in a news release. “The only way to tell if you’ve used too much nitrogen is to compare the rate you used to a lower rate in the same field. A strip in the field with a lower rate, or higher if the field rate is moderate [less than 200 lb per acre from all sources]is a great way to gain confidence in reducing nitrogen levels in the future. »


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