With all the excessive moisture across the Corn Belt this spring, it might be necessary to look at side dressing nitrogen on corn fields that could be at high risk for nitrogen loss.  Nitrogen loss happens in a few different ways when dealing with excessive moisture.

The first cause of nitrogen loss that we are going to cover is denitrification. Denitrification is the process of converting nitrite NO₃- to a N₂ gas which is unusable for plant uptake.  Denitrification happens when soils are overly saturated or poorly drained and have ponding water. When soil saturation of open pore space is greater than 60%, the rate of denitrification rapidly increases. (NDSU Chatterjee).  According to research at the University of Nebraska, the estimated denitrification loss of nitrate when the soil temperature is 55 to 60 degrees F is 10 percent when soil is saturated for five days and 25 percent when saturated for 10 days (2 to 2.5 percent per day). (Iowa State ICM). Fine and medium textured soils are at the greatest risk for denitrification.

The next form of loss is from leaching and usually occurs on coarse soil types with good drainage.  Since nitrate nitrogen is not bound to the soil, it rapidly moves through the soil profile with excess moisture and can be pushed too low for the crop to reach it.  In areas that deal with leaching it is best to plan to split up the total nitrogen needed for optimal yield into at least two, possibly more, applications to ensure minimizing nitrogen deficiency throughout the growing season. 

The last form that we will cover is surface runoff/erosion.  This usually happens in heavy rainfall events in overly saturated soils.  There are farming practices as well as residue management that can help in managing surface runoff/erosion but for this article we are just covering the loss of nitrogen.

Now that we have identified the causes of our nitrogen loss, what do we do about it?

That’s where side dress application of nitrogen comes in.  Side dress applications usually occur between V6 to V8 but may need to be considered earlier if the crop is showing signs of nitrogen deficiency.  The rate of actual nitrogen to apply will depend on a few things including residual nitrogen, yield goal, soil type and form of nitrogen being applied.

Consider doing a preside-dress nitrogen test to determine how much nitrogen is left over for the crop.  Next consider what a realistic yield goal is and plan accordingly to replace any nitrogen that could have been lost.  Lastly consider the soil type that you will be applying the side dress application.  If you’re dealing with coarser soils it might be best to split up the side dress application into another application to ensure proper crop needs. 

For more information contact your local LG Seeds Technical Team Agronomist or Sales Account Manager.

Cited Sources and Additional Information:

1. https://www.ndsu.edu/fileadmin/soils/pdfs/SWW2017Chatterjee.pdf
2. https://crops.extension.iastate.edu/cropnews/2014/06/estimating-nitrogen-losses-wet-corn-fields