How much spring nitrogen to apply? Weather before planting may provide an idea

How much spring nitrogen to apply? Weather before planting may provide an idea

With the rising cost of nitrogen fertilizers and their impact on air and water quality, University of Illinois researchers want to help farmers make informed decisions about fertilizer rates. The latest modeling effort aims to do this by examining the role of pre-growing season weather on soil nitrogen dynamics and end-season maize yield.

"When farmers sow corn in the spring, they already know what happened from the previous fall to the spring." And unlike the upcoming planting season, which we can't predict reliably, we can use pre-sowing season information to guide farmers to adjust the use of corn.

Zhi Li, a doctoral researcher in the Department of Natural Resources and Environmental Sciences (NRES) at the University of Illinois and lead author of the new study published in Field Crops Research, agrees.

Lee's model found that wetter pre-planting seasons reduce soil nitrogen through leaching. With no fertilizer added in the spring, a slight increase in pre-season rainfall reduced yields by 5-14%. But with spring fertilizer applied at about 150 pounds of nitrogen per acre, the 2018 average in Illinois, pre-season heavy rainfall still drops yields 1-3%.

"Our analysis revealed that applying more fertilizer can reduce, if not eliminate, crop loss caused by increased precipitation prior to the growing season." Based on our model, if a farmer from Illinois used 150 pounds of nitrogen per acre, 1-3% could Prevent yield loss by adding about 16 pounds of nitrogen,” Lee says.

In cooler-than-normal pre-planting seasons, soil inorganic nitrogen—and end-of-season yield—decreased due to reduced soil microbial activity and enhanced leaching. But in this case, adding more compost in the spring may not do much.

"Adding more fertilizer will not eliminate the effects of cold pre-season temperatures on the crop," Lee explains. "This is because, in addition to affecting soil nitrogen content, temperature appears to limit early growth in ways that reduce yield potential, even if the weather later returns to normal."

Lee used an advanced agroecosystem model, known as ecosys, to understand how temperature and precipitation in the pre-growing season affect soil inorganic nitrogen content and productivity. The ecosystem model was chosen by the research team because of its advanced ability to simulate carbon, water, and nutrient cycles. The model uses first principles and complex algorithms to simulate management practices and their effects.

"The ecosystem model has been widely used for many different cultivation states, and this study also shows that an ecosystem can perform well in nitrogen cycle simulation." We used validation data from decades of nitrogen experiments conducted by our collaborators in Illinois and other western states.

Middle We found that the model can actually reproduce these patterns, not just the Illinois data, but patterns from the broader Midwest says Kaiu Guan, associate professor at NRES, founding director of the Center for the Sustainability of Agricultural Systems in Illinois, and the study's principal investigator.

“We put in an extensive validation effort; it means a lot because you want to trust a validated model, which is robust. We believe that the results in this work provide some justification for looking at weather prior to the growing season in determining the use of nitrogen fertilizer in the spring” Guan adds. "One of our future studies will look at these factors in the decision-making tools used by farmers."

Guan and Li say the model results can be used to improve the nitrogen rate calculators currently in use. Meanwhile, Emerson Nafziger, professor emeritus in the Department of Crop Science and study co-author, says farmers who want to adjust their nitrogen application may want to consider strip trials as a complementary approach.

“High rates of nitrogen tend to produce dark green corn, but low rates may also. The only way to know if you are using a lot of nitrogen is to compare the rate you used to a lower rate in the same field. In the field, at a lower rate, or higher if The rate in the field was moderate [less than 200 pounds per acre from all sources], a great way to gain confidence in future nitrogen rate reductions.

The higher rate produces enough additional yield to pay for it, we should be able to determine the likely cause of the difference (eg moist soil) and use that to adjust rates in the future,” says Navziger.

The research, titled "Evaluation of the Effects of Pre-growing Season Weather Conditions on Dynamics of Soil Nitrogen and Maize Yield in the American Midwest," was published in Field Crops Research. The research was supported by a National Science Foundation (NSF) Career award, the USDA's National Institute of Food and Agriculture, the Illinois Nutrient Research and Education Council (NREC), and the NSF Signals-in-the-Soil Program.

The Departments of Crop Science, Natural Resources, and Environmental Science are located in the College of Agricultural, Consumer, and Environmental Sciences at the University of Illinois, Urbana-Champaign.


Materials provided by University of Illinois College of Agricultural, Consumer and Environmental Sciences.


Ziyi Li, Kaiyu Guan, Wang Zhou, Bin Peng, Zhenong Jin, Jinyun Tang, Robert F. Grant, Emerson D. Nafziger, Andrew J. Margenot, Lowell E. Gentry, Evan H. DeLucia, Wendy H. Yang, Yaping Cai, Ziqi Qin, Sotirios V. Archontoulis, Fabián G. Fernández, Zhongjie Yu, DoKyoung Lee, Yufeng Yang. Assessing the impacts of pre-growing-season weather conditions on soil nitrogen dynamics and corn productivity in the U.S. Midwest. Field Crops Research, 2022; 284: 108563 DOI: 10.1016/j.fcr.2022.108563


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