Enhancing Nitrogen Use and Effectiveness
March 7, 2022 With all of the discussion about fertilizer supplies and prices heading into the 2022 season, keep in mind that an extensive multi-state research effort on nitrogen is continuing this year with a primary focus on economics and environmental impact – two major aspects of sustainability.
“Right now, the biggest concerns farmers have related to nitrogen management are cost and instability of supply, as well as some of the environmental aspects we’re facing,” says Dr. Katie Lewis, Associate Professor of Soil Chemistry and Fertility with Texas A&M AgriLife Research and Extension, speaking at the 2022 Beltwide Cotton Conferences. “Right now, costs are as high as they’ve been for a long time. It’s very expensive from the standpoint of dealing with demand as well as the potential for environmental aspects to result in large losses of that nitrogen.”
She outlined on-going research efforts developed to improve nitrogen use recommendations on a regional basis and help limit nitrogen losses. A big part of that is evaluating the environmental conditions that can result in losses and find ways to increase plant uptake of nitrogen and reduce environmental impact.
The two biggest concerns from a loss perspective are denitrification and leaching, explains Lewis.
“Denitrification is going to potentially influence climate change with the releases of different nitrogen gases,” she says. “With cotton, one of the concerns with denitrification is that we’re applying larger amounts of nitrogen compared to, say, peanuts. The potential is there for large losses.
“We can also lose billions of pounds of nitrogen across the U.S. through leaching as well as ammonium volatilization,” she adds. “That’s where we could lose 50% to 75% of the nitrogen from an application of ammonium or urea-based fertilizer within a 48-hour period. If we’re not doing things to reduce those losses, then we’re going to have a negative environmental impact as well as an economic impact.”
Taking a Fresh Look at the Four R’s
Decades of research work on management strategies for applying nitrogen fertilizers have been boiled down to the Four R’s – the right rate, the right source, the right time, and the right placement or method of application for that fertilizer.
That provided the starting point for the current research studies, despite questions about “Why are we doing this again?”
“There are new cultivars with different maturities,” explains Lewis. “The uniqueness of the research we’re conducting today is to keep pace with changing technologies.”
The first research project, funded by The Fertilizer Institute, is being conducted by Extension research specialists in Virginia, Georgia, Tennessee, and Texas. The primary goal is to quantify the agronomic response of newer cotton cultivars and their maturities to different nitrogen rates and placement strategies, as well as looking at the associated environmental aspects.
The first component of the study evaluates source, rate, and placement comparing liquid versus dry products with rates ranging from zero to 200 pounds of nitrogen per acre and with different placements (injected, surface, broadcast).
“We’re trying to evaluate how the maturity of different cotton cultivars is going to influence the recommendations so that we can pinpoint what the most profitable nitrogen rate would be,” says Lewis.
A second part of the study focuses on the economic and environmental components of using enhanced efficiency nitrogen fertilizers, looking at placement, application rate, and use of nitrogen stabilizers to help determine how they influence the release of greenhouse gases and the uptake of the nitrogen fertilizers.
The final component of the study measures the impact of various cover crops as a source of green manure. “We’re looking at cover crop mixtures including cereal rye, hairy vetch, and a mixture of the two in different nitrogen application rates and the influence it has on cotton,” notes Lewis.
The researchers completed the third year of the first study component in 2021. That data is now being evaluated for each growing region to help compile nitrogen application rates based on just the rate and method. Those recommendations will be verified in 2022.
The greenhouse gas and cover crop components both enter their third year of evaluation in 2022.
“One of our overall objectives of this study is to develop a comprehensive management guide that informs regional management practices,” says Lewis. “We can’t have one recommendation that’s suited for the entire Cotton Belt.”
A Broader Scope
A second study, funded by Cotton Incorporated, is evaluating rate as well as the contribution of microbial activity to nitrogen availability. It’s being conducted by Extension researchers in eight cotton-producing states – North and South Carolina, Oklahoma, Virginia, Missouri, Texas, Mississippi, and Tennessee.
“We’re working with USDA to look at the mineralization potential,” explains Lewis. “One of the things we see quite commonly across the Cotton Belt is a lack of response to nitrogen application. We’re trying to pinpoint if mineralization from microbial activity in the soil is contributing to that lack of response.
The project is ongoing, with at least one more year of evaluation.
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