Fall Fertilizer Strategies: How to Optimize Nitrogen with Stabilizers
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Nitrogen, a very costly input for corn farmers, is also difficult to manage in the soil. Applying nitrogen in the fall can decrease financial inputs, lessen spring workload and provide more favorable soil conditions, but once applied, it can be lost through leaching, denitrification and volatilization. So, how can your customers take advantage of fall nitrogen applications yet make sure it does not go to waste before spring?
Though nitrogen makes up 78% of the air we breathe, most organisms, including plants, can’t access it until it goes through a process called nitrogen fixation. In this process, bacteria convert nitrogen into ammonium and nitrate. Plants can absorb nitrate for nourishment.1 The issue farmers face is making this nitrogen available to the corn plant for as long as possible, both for the health of the plant and the economics of the input.
Necessary but challenging
Trials indicate corn yields decline over time if nitrogen fertilizer is withheld from the soil.2 Lack of nitrogen inputs also reduces soil nitrogen efficiency and increases oxidative stress.2,3 But this necessary, costly input can also be lost easily — in the water, soil or atmosphere.
Why apply in the fall?
While a spring application puts nitrogen in the soil nearer to plant uptake, excess rainfall can cause losses from leaching and denitrification.4 Spring can also pose risks to nitrogen loss due to potential warm soil temps, lack of rainfall and moist soils that are drying out.5
By contrast, in the fall, soil conditions are generally more favorable for nitrogen application. In addition, handling the task in the fall allows more time for other activities during a busy spring. Ammonia is often cheaper in the fall than in the spring, too, taking a smaller bite out of the farmer’s wallet.6 For these reasons, fall applications make sense for many farmers.
Fall-applied nitrogen: Stabilize it!
Fall application puts nitrogen in the soil about six months before corn can use it. That’s a long period of time with potentially unpredictable soil conditions. Anhydrous ammonia is an effective source for fall nitrogen application because the conversion of ammonia to ammonium in the soil progresses more slowly in fall conditions.7 The sweet spot for application is between 50°F, when nitrification slows greatly, and before soil freezes, which stops nitrification altogether. Once nitrogen is in its nitrate form, it’s more prone to loss from leaching.6 The solution is to add a nitrification inhibitor such as N-Serve® nitrogen stabilizer, which slows down the bacteria that converts ammonium to nitrate. Nitrogen then remains in the ammonium form longer so that it can be there in the spring when the corn is ready for it.
Knowing where to make nitrogen applications will also assist in maximizing the results. Sandy soils, for example, have a high potential for leaching. Also, avoid areas where water may accumulate, as this exposes soil to the risk of loss by denitrification.7
Once the harvest gets going, it progresses quickly. Soon enough, it will be time to begin next year’s preparations. If your customers’ fall plans include nitrogen fertilization, be sure to consider soil temperature, moisture levels and the risk of nitrogen losses. A nitrogen stabilizer such as N-Serve can be a useful tool in ensuring customers get the best results from fall applications.
1 Emma Orchardson, “Nitrogen in Agriculture,” CIMMYT, published December 4, 2020, https://www.cimmyt.org/news/nitrogen-in-agriculture/.
2 Linda F. Benedict and Henry J. Mascagni, Jr., “Influence of Nitrogen Rate on Corn Yield over the Past Decade on Two Mississippi River Alluvial Soils,” LSU AgCenter, October 12, 2015, https://www.lsuagcenter.com/ portals/communications/publications/agmag/archive/2013/spring/influence-of-nitrogen-rate-on-corn-yield-over-the-past-decade-on-two-mississippi-river-alluvial-soil.
3 Fernando Galindo et al., “Impact of Nitrogen Fertilizer, Sustainability on Corn Crop Yield: The Role of Beneficial Microbial Inoculation Interactions,” BMC Plant Biology, April 11, 2024, https://bmcplantbiol. biomedcentral.com/articles/10.1186/s12870-024-04971-3.
4 Christopher Graham and Anthony Bly, “Chapter 20: Corn Nitrogen Timing, iGrow Corn: Best Management Practices,” South Dakota State University, 2016, https://extension.sdstate.edu/sites/default/ files/2019-09/S-0003-20-Corn.pdf.
5 John Sawyer, “Spring Corn Nitrogen Fertilization Considerations,” Iowa State University Extension and Outreach, March 12, 2020, https://crops.extension.iastate.edu/cropnews/2020/03/spring-cornnitrogen-fertilization-considerations.
6 Emerson Nafzinger, “Is Fall a Good Time to Apply Nitrogen?” Department of Crop Sciences, University of Illinois, September 30, 2020, https://farmdoc.illinois.edu/field-crop-production/is-fall-a-goodtime-to-apply-nitrogen.html.
7 Fabian Fernandez, “Fall Nitrogen Fertilizer Application: The What, Where, When and How,” Minnesota Crop News, October 4, 2022, https://blog-crop-news.extension.umn.edu/2022/10/fall-nitrogenfertilizer-application.html.
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