Andrea Rice, MoFCB Director of Research, Education, and Outreach
Missouri Fertilizer Control Board has approved Phase II of the nitrogen study through the University of Missouri with Dr. Kelly Nelson leading the research team. The team successfully completed Phase I with research station studies with Phase II moving into on-farm trials. The results of this N project as well as P, K, and S studies will be integrated into an online tool for producers and retailers/advisers.
Phase I of the Biological N study was successfully implemented with a diverse set of experiments along with the collection of plant samples, soil samples, and other data supporting the project’s goals. All research tested at least one biological factor for its impact on nitrogen response as defined by a nitrogen rate response curve.
From the data collected in Phase I, the following early conclusions can be made on N response:
• There was no evidence biologicals (bug-in-a-jug) reduced nitrogen fertilizer recommendations or increased yield in six robustly designed experiments at three locations, two in the Bootheel and two in Northern Missouri. Additional site-years are recommended to expand evaluation of environmental (weather) impact.
• This project is the most comprehensive assessment of the impact of landscape position on nitrogen response of crops ever implemented in Missouri, and included assessments of corn, tall fescue, and rice. Landscape impacts were complex and varied significantly across locations, crops, and years. In corn, the amount of nitrogen needed differed with landscape positions in experiments at both GREEC and CREEC, but only affected yield at GREEC. In tall fescue, landscape position consistently affected yield, but did not always impact the nitrogen needed to optimize yield. Additional site-years are needed to better characterize the interactions of crop, soil characteristics (e.g. topsoil depth), and weather (e.g. precipitation) driving the complex impact of landscape position on nitrogen response. This research shows the greatest potential for advancement on-farm.
• Two different experiments, each with two site-years of data, suggest that nitrification inhibitors typically had the intended impact of attaining maximum yield at reduced nitrogen rates when used with anhydrous ammonia. Factors such as landscape position and timing impacted results. The important role of weather suggests the benefits of more site-years of data.
• In contrast to data from extensive previous Missouri research, cover crop ahead of corn had no significant impact on yield potential of corn or the nitrogen rate needed to maximize yield in 12 comparisons in central Missouri over two years. Dry conditions contributed to poor stands and low biomass at termination, which may have resulted in a lack of response to cover crop.
• Residual inorganic nitrogen in the top 18 inches of soil has not been well correlated with nitrogen rate across several corn experiments. Also, spring tall fescue was less responsive to projected residual nitrogen carry over from the previous fall. The mechanisms causing this outcome are still being investigated.
These results focused on treatment impacts at a location or year on yield, but there has been limited effort to date to integrate experiments across locations and to explain why responses differ by location, year and landscape. Data is being collected at each site on initial soil health and fertility test levels, landscape position, nutrient uptake by the crop, cover crop characteristics at termination (when relevant), weather, and other potential explanatory variables. The data will be synthesized into a database under development by the direction of the soil fertility working group and a post-doctoral fellow hired onto this project.
The University of Missouri research team shares a commitment with MoFCB that data from these experiments will be fully accessible to the public. Additionally, there is a need for project data to reside in a central location to facilitate the integration of results envisioned by this project. To facilitate both objectives, a prototype website, available for demonstration, was developed with an interface that allows users to find experiments of interest and then generate graphs comparing treatment effects on nitrogen response. We anticipate deploying the first version of the website to the public in 2025. The full development of the website will remain a component of the project through Phase II.
Information for this blog was taken from the report provided by the University of Missouri research team for the Missouri Fertilizer Control Board.