Agronomic and economic evaluations of N fertilization in maize under recent market dynamics

Authors: Mohammed, Yesuf; Gesch, Russell - Russ; Johnson, Jane; Wagner, Steven

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2022
Publication Date: 9/1/2022
Citation: Mohammed, Y.A., Gesch, R.W., Johnson, J.M., Wagner, S.W. 2022. Agronomic and economic evaluations of N fertilization in maize under recent market dynamics. Agronomy. (3):514-527. https://doi.org/10.3390/nitrogen3030033.
DOI: https://doi.org/10.3390/nitrogen3030033

Interpretive Summary: Nitrogen (N) fertilizer is one of the main input costs for corn producers. Nitrogen fertilizer rate determination for corn production in Minnesota is mainly based on an online calculator available for Corn Belt Regions. This calculator considers N fertilizer cost, corn grain price and rotation (maize after maize or maize after soybean) to determine how much N fertilizer to apply to grow corn in Minnesota. This method recommends the same N rate for the entire state of Minnesota. But we know that soils in this state are different (for instance parent material varied which affect the soil texture that will affect nutrient availability including nitrogen). In addition, weather (temperature and rainfall) varies when going from south to north and from east to west across Minnesota. All these factors together with recent changes in cost of N fertilizer and corn grain price may affect the rate of N fertilizer determination using this calculator. Therefore, we compared results from field study with the recommendation from this calculator to the see the net benefits of using N fertilizer for corn production. The results from the field study as well as the online calculator showed that the use of N fertilizer is still economical under the current N fertilizer cost. However, when comparing the economically optimum N rate (rate above this will not bring economic benefits) from the field study and the online calculator, the field study estimates 149 pounds of nitrogen per acre, but the online calculator estimates 135 pounds of nitrogen per acre. Generally, the N fertilizer rates estimated by these two methods are very close. But to minimize possible N deficiency and yield penalty, some refinement on the online calculator is needed to use it as a best tool for N fertilizer determination. These may include considering weather, soil types and corn hybrid (early vs. late) to better estimate N needed for corn production in Minnesota. This finding gives insight for researchers and agronomists to improve the online calculator for better N fertilizer estimation for corn production. In addition, the results provide the needed information for extension specialists, consultants and producers interested in to know the effects of the current N fertilizer cost and corn grain price on the net benefits of using N fertilizer for corn production.

Technical Abstract: In Minnesota, a Corn Belt based online-calculator is available for determining economic nitrogen (N) fertilizer rate for maize (Zea mays L.) production. The calculator considers N fertilizer cost and maize price together with previous year crop history and estimates the same N rate for all Minnesota locations based on maximum return to N (MRTN). However, a clear precipitation and temperature gradient, and soil heterogeny across the state, together with recent market volatility of fertilizer cost and grain price requires revisiting net benefit of N rate determined from this calculator compared with results from the field study. A two-year study was conducted to compare agronomic and economic optimum N rate from field experiment and online-calculator. Nitrogen fertilizer ranged from 0 to 224 kg N ha-1 and either all the rate applied at planting or split applied. The results showed that grain yield had a quadratic response to N rates and agronomic maximum yield peaked at 205 kg N ha-1. The economic optimum N rate (EONR) from the field trial was 168 kg N ha-1 and it remained stable under wide economic analysis scenario-cases. The net benefits varied based on scenarios and reached up to 2,474 USD ha-1. The N rate from the online-calculator at MRTN was 151 kg N ha-1. This may be insufficient based on the field experiment and could cause N deficiency resulting in a yield penalty. We suggest using some adjustment factor/s or alternative site and maize hybrid specific information in the model to refine the online-calculator as a best tool for N fertilizer rate determination.