Revamping nitrogen fertilizer recommendations for Missouri

Authors: SINGH, GURBIR - UNIVERSITY OF MISSOURI; LORY, JOHN - UNIVERSITY OF MISSOURI; NELSON, KELLY - UNIVERSITY OF MISSOURI; DAVIS, MORGAN - UNIVERSITY OF MISSOURI; Abendroth, Lori; KAUR, GURPREET - UNIVERSITY OF MISSOURI; CALHOUN, JUSTIN - UNIVERSITY OF MISSOURI; CHLAPECKA, JUSTIN - UNIVERSITY OF MISSOURI

Submitted to: North Central Extension Industry Soil Fertility Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 11/13/2023
Publication Date: 11/15/2023
Citation: Singh, G., Lory, J., Nelson, K., Davis, M., Abendroth, L.J., Kaur, G., Calhoun, J., Chlapecka, J. 2023. Revamping nitrogen fertilizer recommendations for Missouri. Proceedings of 53rd North Central Extension-Industry Soil Fertility Conference, November 15-16, 2023, Des Moines, IA. p. 206-212. Available: northcentralfertility.com/files/NCSFC_2023_Proceedings.pdf

Interpretive Summary: Recommendations for the application of synthetic nitrogen fertilizer in Missouri were last updated by the University of Missouri twenty years ago. These recommendations are based on a farmer’s yield goal with some adjustments for management practices and soil organic matter content. The use of a yield goal to determine the amount of fertilizer to apply in a particular year can be detrimental due to the potential for overapplication and offsite losses of nitrogen. To improve nitrogen recommendations, our research team is conducting extensive nitrogen rate studies in corn, cotton, and rice systems. Additionally, information is needed for farmers who are seeking to improve the biology of their fields by altering management practices such as cover crops and reduced or no-tillage and to reduce off-site nitrogen loss by incorporating products such as nitrogen stabilizers and biological nitrogen efficiency enhancers. We are conducting experiments to quantify the influence these biological products and practices have on the nutrient cycling in the soil which may result in a potential reduction in the needed amount of nitrogen fertilizer. Findings from one site and one year are included as an example of the type of data the team will be analyzing from the 3-year project (2023-2026). This research will directly benefit Missouri farmers and agribusiness personnel by providing robust recommendations for the region on how much fertilizer to apply based on specific field practices, crop type, and soils.

Technical Abstract: Multiple nitrogen (N) fertilizer rate decision tools have been developed over the years for recommending N to growers. These tools are based on mass balance equations with expected yield and yield goal, economically optimum N rate, preplant soil nitrate test, pre-sidedress and late spring soil nitrate test, plant tissue nitrogen, crop growth models, and canopy reflectance sensing. These tools rarely include biological N in the rate recommendations. Advances in soil health assessment providing soil health scores and soil respiration estimates have been documented to improve N recommendations for corn in the Midwest. In Missouri, N fertilizer rate recommendations are based on yield goals and include organic matter adjustment factors for most crops. This N recommendation system does not integrate practices that improve soil health such as cover crops, applying biological N efficiency enhancers to increase plant-available nitrogen, N stabilizers such as nitrification and urease inhibitors, and variations in N supply across the landscape. A multi-site project funded by the Missouri Fertilizer Control Board began in 2023 to address these gaps and connect soil health practices and N supply to N fertilizer recommendations for Missouri. The specific objectives are to quantify the N impact of biological input products; cover crops; nitrification inhibitors; and other biological management technologies on N supply, evaluate soil health indicators and weather data as predictors of changes in landscape position and soil conditions impact productivity and soil organic N supply at different landscape positions, calibrate the integration of soil health measurements into fertilizer N recommendations, and improve calibrations of inseason N prediction tools. To achieve these objectives, 12 multilocation trials were established in Missouri in 2023 and first-year results are presented from upstate Missouri sites.