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Current maps show area not at risk for nitrogen losses in corn

Posted Wednesday, June 22, 2011, at 11:00 AM

Excessive rainfall as in past years has raised the question as to is there any nitrogen loss and do I need to apply additional nitrogen (N)?

This growing season is difficult to analyze additional nitrogen needs in general terms due to the variability in amounts and frequency of precipitation as well as the large range of corn planting dates and growth.

This year, fall applications were subject to some N loss.

Fall applications done correctly (in terms of soils and soil temperatures) were not subject to large N loss because a lot of the rain fell early in the spring, when soils were still cool and much of the N had not transformed to nitrate.

Areas that had a lot of rain later, when soils were warm, might have had greater N loss.

In some parts of the state, torrential rains have caused water to puddle in low-lying areas of fields and causing N loss through denitrification.

Spring preplant anhydrous ammonia applications have been less subject to loss because most of the N stays in the ammonium form for a while and is not subject to loss even if soil conditions turn wet after application.

At this point in time there are several soil tests or tissue tests that can analyze the status of the soil nitrogen but may be difficult to get adequate samples or timing of the results may not be indicative what will be available for the plants future use.

Peter Scharf has created a web page that tracks spring precipitation totals and highlights areas that are most at risk.

He updates this page weekly.

The website can be found at http://plantsci.edu/nutrientmanagement/. At this site he has "Nitrogen Watch 2011."

Maps are available that indicate which areas of the state are at risk for nitrogen loss.

This only indicates that producers need to be aware and watch their crop.

Maps are available for different silo textures at this site. Current maps (June 12) indicate that central Missouri is not in the danger areas for either well- and moderately well-drained soils or for poorly- and somewhat poorly drained soils.

If you decide that you need to apply additional N, sidedress earlier rather than later in crop development is at all possible.

If you have options for how to apply N at sidedress, first choice is injection or dribbling UAN solution between rows, second is broadcast of solid ammonium-containing fertilizers, and third is broadcast UAN solution.

Urea granules will have the least impact on leaf burn compared with UAN or dry products but urea is subject to volatilization if rain does not fall within three or four days after application.

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As our local University of Missouri Agronomy Extension Specialist, Crook has been writing a column for the print edition Agriculture page for the past three years and we will now be sharing it on our web version. Crook has a bachelor and masters degree in agronomy from University of Missouri and received his doctorate in Agronomy from Kansas State University. He was in soybean variety development research for 22 years for various seed companies and has been Saline County's agronomy specialist for 10 years.
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