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If the latter half of the 20th century was about an herbicide revolution in agriculture, the early 21st century will be about nitrogen (N). Public and private researchers are focusing on its role in boosting corn yields above the current average high-yield mark of 164 bu. Seed companies feel they can eventually push this to 300 bu. to meet growing global demand.
“It will be of immense concern to agriculture for at least the next 20 years,” says Tony Vyn, Purdue agronomy professor.
Improving corn’s N use efficiency (NUE) will not only increase yields, but also decrease the amount of runoff. Vyn says there are two avenues to improving NUE: To improve the efficiency of capturing the inherent soil N, and to increase fertilizer N’s efficiency.
Between 1965 and 2010, N use has increased from an average of 75 lbs./acre to 140 lbs./acre, according to the USDA. However, a study by Vyn and colleagues show that current corn hybrids are more efficient in their N use.
Purdue University researchers looked at studies conducted over the past 72 years. They found that 1 lb. N now produces 22% more grain than it did in 1940 (49 lbs. vs. 56 lbs. of grain). Corn’s NUE has improved mainly because corn makes more grain for every pound of N taken up by plants over the growing season, but why that happens is less clear, Vyn says.
About 40% of the plant’s total N is taken up after flowering in modern hybrids, Vyn says. Furthermore, simply looking for hybrids with the darkest green leaves, which suggests healthy N metabolism, may have no bearing on a plant’s final yield or its final NUE.
“So what we’re trying to figure out when and what to measure – and whether you can do this successfully in an automated greenhouse.”
Lloyd Murdock, soil specialist at the University of Kentucky, says research in the state shows similar increased efficiency over the last 10 years. Where it once took 1 lb. N to increase yield 1 bu./acre, it’s now closer to 0.75 lb.