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Nitrogen Supplements (05/21/15)

There are three reasons why growers might need to consider supplemental N fertilizer a little later on in the growing season.

Nitrogen Supplements

There are three reasons why growers might need to consider supplemental N fertilizer a little later on in the growing season. The first is because some growers succumbed to talk of drought and decided to error on the side of lower yields and lower N rates. If this happened, the recent recharging of the subsoil in the state (the whole state, really), has changed the yield outlook. Pay attention to the wheat and corn N calculators, because these are economic based. It doesn’t make any sense to pay $10 to make $5; people can grow broke that way. But if there is a difference between what was applied and what is needed based on the calculator, then planning for topdress/sidedress N is in order.

The second reason is if wheat growers planned to go for bushels to offset low grain prices and chose a high yielding variety such as Faller to make this happen. What was not considered enough is that in years of low grain prices, protein varieties trump high yielding varieties for return. If a growers’ Faller makes 100 bushels per acre, wheat price is $5/bushel at harvest, but the dock for 12% protein is $2 per bushel, does $300 per acre pay for expenses. If a growers’ Glenn under similar conditions made 80 bushels per acre, but hit 14% protein, $400 looks a lot better than $300 per acre. So given the rainfall we just had and cooler temperatures and high temperatures not in the foreseeable future, higher yields and lower protein are also in your future. Therefore, to minimize protein discounts, supplemental N between now and jointing would be a very good plan unless it hits 110 degrees somewhere in the next few weeks and doesn’t rain again this summer.

The third reason for considering supplemental N is N loss from high rainfall in the eastern 2/3 of the state. A 4-8 inch rain over several days will both leach N from sandier soils, particularly hilltops and slopes, and produce denitrification losses in higher clay soils. In the Fargo area, for example, the soils have now been muddy for at least 8 days. Basing the following estimate on similar conditions in 2010, 2011, 2013 and 2014, we probably have lost over 20 pounds of N so far in these soils and the corn is barely up. Any additional rain and muddy days in high clay soils will result in losses of about 1.5% per day. A high N strip would more accurately illustrate any losses, but without such a strip, using the estimate will be in the ballpark.

For small grains, stream-bars or urease inhibitor (NBPT products such as Agrotain® or another NBPT containing product, or Limus® from BASF, which contains NBPT and NPPT, are effective- no other chemistries available in the USA have been shown effective) treated urea would be recommended up to jointing. Protein enhancement only is recommended immediately post-anthesis, in a Crop and Pest Report to be named later. Corn side-dress can happen anytime after planting, but is ideally applied from V4 to V8 before the large corn N demand kicks in.

A word of caution for those interested in Y-tubes: This apparatus was designed in the central corn belt. Having worked there nearly half my career, nearly every morning the corn plants are wet with dew; really wet, soaking wet with dew. Walk into a corn field in central Illinois at 6AM and your jeans will be wet to the thighs within 20 feet of the ditch. Here, many mornings there is hardly any dew at all. Sometimes, there is, and most times there is not. We do not have the early morning water that would make a Y-tube as effective as in moister climates. If there is no dew, streaming in the mid-row is just as good.

Just saying.

Dave Franzen

NDSU Extension Soil Specialist

 

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