Managing crop residue to reduce optimum nitrogen fertilizer inputs and increase yield

Aug 2021


There is growing evidence that the amount of both corn and soybean residue affect the optimum nitrogen fertilizer rate to the following corn crop. Higher levels of residue lead to higher optimum nitrogen fertilizer rates. However, recommended nitrogen fertilizer rates do not consider the amount of residue from the previous crop.


This project will determine the ability for farmers to adjust optimum nitrogen fertilizer rates based on the amount of corn and soybean residue production in the previous year’s crop. A well-established relationship between residue production and optimum nitrogen fertilizer rate would allow farmers to: i) better manage nitrogen fertilizer inputs as they vary from field-to-field and year-to-year as a function of residue production, and ii) manage residue for lower optimum nitrogen rates.


Researchers will conduct nitrogen fertilizer rate trials in continuous corn and corn following soybean for two years at four locations in central and eastern Iowa. They will adjust aboveground residue inputs in replicated plots according to the following five levels, 300, 250, 200, 150, and 100 bushels per acre, for corn residue preceding corn (i.e., continuous corn) and 80, 70, 60, 50, 40 bushels per acre for soybean residue preceding corn (i.e., corn-soybean rotation). Researchers will then use the APSIM model to determine the relative effects of interannual weather variation and crop residue amount on the maximum return to nitrogen (MRTN).

Project Updates

Note: Project reports published on the INRC website are often revised from researchers' original reports to increase consistency.

April 2024

We conducted three experiments where we measured the effects of residue management (both corn and soybean) on the following corn yield and nitrogen fertilizer requirements. Harvesting of soybean residue in a no-till corn-soybean rotation consistently increased the nitrogen use efficiency of the following corn crop (that is, either the optimum N fertilizer rate was reduced, the corn yield at the optimum N fertilizer rate was increased, or both). In corn following corn, residue harvest had inconsistent effects on corn yield and the optimum N input.

Other activities 

The project was featured in one field day and one presentation. 

One proposal was submitted: The Iowa Soybean Association provided $30,000 to model the data coming out of this project.

July 2023

Research plots have been established for the 2023 growing season. These plots have been moved to new sites on ISU research land. Since January, these plots have been planted, stand counts taken, sensors have been implemented to investigate differences in soil conditions, and weekly soil samples have been taken.

Findings for the 2022 growing season include: For the site in corn on corn rotation with tillage, removing residue produced higher yields in lower nitrogen rates (0-225lbs/acre). In contrast, residue addition produced higher yields in high nitrogen rates (300 lbs/acre). Residue removal also had a lower AONR when compared to residue addition. The site in corn on soybean no-till rotation (planted in corn in 2022) removing residue increased yield in all n-rates. Removing residue had a higher AONR when compared to residue addition, a large contrast to the corn-on-corn experiment.

Other activities and accomplishments

In February,, published an article about research done through this project on soybean residue. Dr. Micheal Castellano contributed to this article through an interview and by providing images.


December 2022

Plots were plant sampled to compare dry weights and carbon to nitrogen values. In November, plots were harvested for yield data. New farms have been selected for the 2023 growing season, these farms have been soil sampled, residue sampled, and the new residue treatments have been put into place.

June 2022

Since the last report, plots in this study have had sensors installed, soil samples taken, nitrogen treatments applied and planted. Plots will continue to be soil sampled and monitored for emergence.


December 2021

In October field sites were flagged, soil sampled, and respective corn and soybeans residue treatments were implemented after crop harvest. Soil moisture and temperature sensors we ordered and plans for employment in field sites were put in place for early March of 2022.

Other Activities 

-1 presentation,

Proposals submitted:

- 4.

We submitted proposals to Iowa Farm Bureau, Iowa Corn, and Iowa Soybean and received funding from all three - Total cumulative dollar amount requested from all submitted proposals: $293,000