A University of Guelph study shows that split nitrogen applications in corn bring an economic and environmental benefit to producers.
It can increase farm profits by 15 to 20 per cent in dry seasons compared to pre-plant broadcast.
It also showed a small profit increase by making the second application of N during V13 rather than V6.
Why it matters: Split N application can help farmers save money and reduce environmental impact by following the 4R nutrient management plan, specifically the “right rate”.
Researchers identified situations where split nitrogen makes sense economically and environmentally. The key economic benefit lies in farmers’ ability to be more adaptable in mid-season fertilizer application.
“The idea with split application is although it’s more costly [compared to a pre-application], the benefit is you can adjust based on in-season weather,” says Joshua Nasielski, assistant professor with the University of Guelph.
“Is this a year where my yield potential is shot? In that case, the best split application strategy is to not apply any at all.”
“What split application allows you to [do is] increase the sufficiency of nitrogen. It allows you to either apply less or apply the appropriate amount, so it is not lost,” says Aaron Delaporte, research associate. “If it’s dry you need less nitrogen and if it’s wet you might need more.”
Producers can realize higher margins in dry years by reducing nitrogen rates without affecting yield.
“Because water was limiting yield more strongly in dry years, one could go down from 150 pounds of nitrogen per acre to 115 pounds of nitrogen per acre, while keeping yield the same,” says Nasielski.
That increased profit by about $10 per acre over a pre-plant broadcast of 150 lb. per acre of N.
“When you reduce your N rate in dry years, the cost savings on N fertilizer are large enough to cover the cost of custom application of split-apps and then some. The overall profit can increase by $10 per acre even after the cost of custom application is accounted for,” says Nasielski.
For a farmer who split-applies N but doesn’t reduce the rate, the fertilizer costs are the same, but the cost of custom application is estimated at $12 per acre.
“Split applying N without adjusting the N rate would cause a farmer to lose money in dry years,” says Nasielski.
The researchers said they assumed $12 per acre for custom application based on provincial government data.
A small profit increase was found by applying the second N application at the 13-leaf stage compared to the six-leaf stage of corn growth.
“This was probably due to less N loss at V13 versus V6, on average, so more N was available to the crop,” says Nasielski.
The study showed a decrease in nitrogen leaching and denitrification at V13 because the corn crop is actively taking up water, reducing the risk of losses. By waiting for V13, producers also have a better idea about potential yield.
Nasielski says he always advises farmers to fertilize based on average yield and adjust the rate for the second application.
“By V13 you have a better idea of whether you are in a high yielding year. This will save you money in the long-run [with] reduced cost in average years, benefit the environment [with] reduced losses and still allow the farmer to take advantage of good years by topping up in-season,” says Nasielski.