Zeroing in on precision N rates
Agronomists have long admitted that nitrogen recommendations for corn generally aren’t too accurate. Plus or minus 40% accuracy isn’t very good, particularly with today’s rising concerns over Chesapeake Bay nutrient pollution.
“Today, we can have far better than plus or minus 40% accuracy,” says Harold van Es, Cornell University’s Department of Crop and Soil Sciences chairman. In fact, his 18-year-old idea of tailoring N applications with a field-specific tool is field-ready.
In 2010, the Adapt-N software was field-tested in New York and Iowa, and it passed muster. This year, it’ll be tested even more.
• The Adapt-N program helps determine nitrogen sidedress needs.
• The Web-based tool uses local climate data for specific fields.
• It lessens the chance of yield reductions due to a shortage of N in the soil.
USDA’s Natural Resources Conservation Service will help fund formal Adapt-N testing on 25 farms across Iowa in 2011 and 2012, reports Jeff Melkonian, the Cornell research agronomist heading the development program. “We’ll have approximately 20 strip trials across New York in 2011,” he adds, “on grain and silage corn fields, as well as sweet corn.
“The Adapt-N tool provides more precise, field-specific N recommendations based on early-season weather’s impact,” he explains. “In warm weather, nitrogen mineralizes faster from organic matter in the soil to become available to the corn; the opposite is true in colder weather.
“In a drier spring, N mineralizes and remains in the root zone, where the corn can take it up. In a wetter year, the nutrient may leach out of reach of the crop roots,” Melkonian adds.
What Adapt-N can and can’t do
Corn nitrogen needs still must be determined the normal way. As Dave DeGolyer, Western New York Crop Management Association’s executive managing consultant points out: “The Adapt-N tool determines if more N is needed at side-dressing time depending on site-specific rainfall.
“Excessive rainfall will cause denitrification or leaching away of that N. Adapt-N will allow producers to more precisely adjust sidedressing rates based on rainfall,” he says. “I don’t think Adapt-N will save on N. Rather, it’ll lessen chance of yield reduction by dialing in the proper rate to sidedress.”
Melkonian contends more accurately estimating N needs will allow spending less money on fertilizer about three out of four years, by adjusting rates based on spring weather conditions. With this tool, for instance, there’s no need for in-season soil sampling or waiting for test results.
Computerized soil-process models of carbon and N transformations are the key drivers of Adapt-N calibrations, he adds. He’s referring to the changing mineralization rate of organic matter, crop uptake, denitrification and ammonia volatilization.
“We’re fortunate in that [van Es’s] research group has collected these data for multiyear studies of grain and silage (i.e. manured) corn cropping systems. However, we’d benefit from additional research.”
Learn more about it at adapt-n.cals.cornell.edu
This article published in the February, 2011 edition of AMERICAN AGRICULTURIST.