Exploring virtual nitrogen fertilizer research plots in Minnesota corn fields
by Greg Klinger
Every spring, as tractors and planters spread out across rural Minnesota, seeding the earth with what will become the annual crop of corn, soybeans, wheat and other agricultural commodities, University of Minnesota researchers are out in full force, as well. They use flagging and GPS to establish research plots on University research farms or private farms across the state, planting and fertilizing these controlled experiments in order to expand our knowledge on how to effectively manage insect pests, diseases, and nutrients.
This research can have important impacts on water quality. For instance, nitrogen fertilizers are the main source of nitrate, a contaminant commonly found in lakes, rivers and drinking water in Minnesota. At the same time, the use of nitrogen fertilizers is critical to obtaining and maintaining high yields in many field crops. It is hard to know what the “right” amount of nitrogen fertilizer is from a farmer’s perspective.
This reality hit home for me in a recent series of nitrogen fertilizer rate trials I participated in, where small plots that received a wide range of different fertilizer rates were established on a number of farms starting in 2015 in order to determine what rates would be most profitable for farmers to apply. One farmer who participated had research trials on three different cornfields in 2016, 2018, and 2019. All of these fields were managed very similarly, but the rate of nitrogen fertilizer that was most profitable for the farmer to apply ranged from 118 to 270 pounds of nitrogen applied per acre over those three years. How can anyone feel confident in their fertilizer decisions with that amount of variability? Any specific nitrogen rate a farmer picked from within that range would result in a significant loss of income from either limited yields or unneeded nitrogen fertilizer in some years (any leftover fertilizer tends not to stick around for next year’s crop), and potentially in more nitrate getting into water supplies.
While there is no magic bullet to help farmers manage their fertilizers, there is, fortunately, other data we collect on these trials that can help farmers make these challenging decisions. This data is complicated to make sense of. To aid in this process, I developed a tool to visualize a research trial for interested farmers with some colleagues in Extension using 3-D photography. This tool, seen here, allows farmers to virtually “step inside” this cornfield in late August to see how the plots look, and it contains a number of embedded videos that discuss some of the data we collected from this and other trials. The videos also discuss how to interpret some of the data, and trends we’ve seen in this data. And, in true Covid-19 fashion, they’re all recorded from my home office! Feel free to explore this tool to understand some of the complex decisions farmers have to make. For a deeper look at how nitrogen fertilizers relate to nitrate in water, take a look at the embedded video “Preplant and residual soil nitrate tests.”