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Don’t Delay Planting to Apply Nitrogen

In-season applications can work to supply corn with N.

If you’re trying to prioritize nitrogen (N) application, planting, and weed control this spring, place N application on the back end.

That’s the word from Peter Scharf, University of Missouri Extension nutrient management specialist. In Missouri, he says time is running out to apply N before corn planting. The good news is N applications after planting are likely to work equally well. 

He adds split N applications—before and after planting—normally work well. However, this year is an exception. 

Rain and flooding kept many farmers from applying N at their usual time.

Delayed Planting Costs Farmers Money

Planting and weed control should take priority over nitrogen application, he says, “Delayed corn planting can cost a lot of money and could have a domino effect on other time-sensitive operations,” Scharf says.

To save time, a single application of dry or liquid N might be the answer this spring rather than split N applications or anhydrous ammonia.

Anhydrous ammonia remains the cheapest N source. It also resists loss best after excessive rains. But it is the slowest to apply, and that is not a good fit with the current situation, Scharf says. 

Nitrogen Myths 

In “Flex and Go Fast,” a new article this month on MU’s Integrated Pest Management website ipm.missouri.edu/IPCM/2019/4/nitrogen, Scharf dispels common myths about N: 

Myth 1: Early-season N stress reduces row numbers on corn ears and cost a lot of yield.

Scharf says he counted ears on continuous no-till corn plots that had no nitrogen for 11 years. Yield suffered but corn ears were reduced by only 0.3 rows.

Myth 2: N applications at waist-high lead to economic devastation.

Scharf’s study of data from five states over three decades shows this to be wrong. He says that data shows the same yield from N applied in a single shot at waist-high as at planting. He does not recommend waiting that long, but if does happen, it is not the huge problem that many people perceive it to be.

Before the ground dries enough to plant, Scharf suggests that farmers write down options and contingency plans for N application. Check with suppliers to see which forms of N are available and in what quantities. With potential transportation issues because of flooding, check on how fast they can get more. Also check availability of high-clearance applicators and planes as a final option.

Scharf recommends broadcast dry N (urea with NBPT or ammonium nitrate) as the best option this year if you have significant residue on fields. Broadcast dry N before planting or any time up to waist-high. Avoid applications of ammonium nitrate after knee-high, which can cause enough leaf burn to reduce yields. Broadcast UAN tends to get tied up on the residue, so it is not a good option on this type of field. Injected UAN is slower than broadcast UAN but still considerably faster than anhydrous.

Broadcasting UAN is fine if you have minimal residue. “This becomes a fast and reasonable option,” Scharf says.

There is little reason for concern over loss due to excessive precipitation if you applied ammonia during the fall, Scharf says. 

“Most of it was applied late and soils stayed cold and wet. The bacteria need oxygen and warmth to convert ammonia to nitrate, so that probably has gone slower than normal.”

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