With all of the flooded soils and wet fields there likely are questions on denitrification and whether side-dress nitrogen (N) should be applied. The fact is that it can be difficult to predict the amount of N lost. However, two things should be considered when dealing with denitrification:
- Denitrification only occurs when nitrogen is in the nitrate form. For fall applied N as long as application occurred after the soils cooled down to appropriate levels then the risk of N loss over the winter and in early spring should be low, especially since soil temperatures have been fairly low for most of the spring.
- Denitrification is due to microbial processes. Therefore, as soil temperatures decrease microbial activity decreases and the risk for denitrification decreases.
U of M Supplemental Nitrogen Worksheet for Corn
Side-dressing N is a viable option if it is determined that some N loss has occurred. Generally, the earlier N can be applied when side-dressing, the better. Although N uptake occurs throughout the growing season, peak demand generally starts at the V5 growth stage and progresses to tasselling, at which time about 60% of the total N is taken up by.
There is no exact recommendation for the amount of supplemental N to apply after crop emergence. Use sound judgment in making rate decisions. The supplemental N worksheet suggests a range of 40 to 70 lb N/acre if corn meets certain criteria. According to Dr. Gyles Randall, a supplement of 30 to 40 lb N/acre is sufficient for corn following soybean on most soils or where corn follows corn on silt loams or sands. However, higher rates (60 to 70 lb N/acre) may be needed for corn following corn on heavy soils.