Strip trials an effective way to test nitrogen rates on cornfields

COLUMBIA, Mo. — On-farm strip trials are an effective way for farmers to test their nitrogen fertilizer rate on corn.

“A wet May has lots of farmers wondering about the nitrogen status of their corn crop,” said John Lory, University of Missouri Extension nutrient management specialist, in a press release. “Wet conditions and warm soils can lead to nitrogen loss of fertilizer.”

Lory said MU research shows that it pays to side-dress nitrogen fertilizer on deficient corn past tasseling, with full yield expected with applications as late as V12 to V16.

Judging how much nitrogen is needed can be difficult, he said, but “nitrogen strip trials offer a way to test your nitrogen rates on your fields under your conditions.”

Some farmers are concerned about the cost of lost yield with a strip trial. The “MU Certified” Strip Trial Program uses a design that limits the cost to the farmer.

“We promote farmers comparing three rates repeated multiple times across the field: the farmer rate, an addition of 30 pounds of nitrogen per acre and a subtraction of 30 pounds of nitrogen per acre, compared to the farmer rate,” said Lory.

This design has two benefits, he said. First, there is no change in the amount of fertilizer applied to the field, so there are no extra fertilizer costs. Second, if your rate is too high, there will be no yield loss from the trial. All three rates will yield the same.

If your rate is near optimum, the lowest rate will yield less than the rest of the field. That loss, when averaged across the three treatments, will average a couple bushels per acre or so. The value is that you know you are making good decisions about fertilizer nitrogen rates on your cornfields, Lory said.

Larger yield losses are possible if your nitrogen rate is below optimum. But this cost highlights much larger losses you likely have on all your corn acres.

Lory recommends doing one or two trials every year on your corn acres. By tracking results across multiple years, farmers will get customized feedback on their nitrogen decision-making.

“This can pay off in the long run in higher yields or lower fertilizer costs,” said Lory.

The “MU Certified” Strip Trial Program is happy to work with farmers interested in doing nitrogen strip trials. Learn more at http://striptrial.missouri.edu.