Nitrogen (N) is essential to plant growth. As a constituent of protein, it is instrumental in critical plant functions from germination to senescence. As a component of the chlorophyll molecule, nitrogen has a primary role in photosynthesis and therefore yield accumulation in crops. Unfortunately, this critical plant nutrient can be easily lost from the soil by leaching or denitrification when excessive rainfall occurs (Figure 1).
When early-season N losses occur, or wet conditions prevent applying N early, rescue applications can be an effective remedy for corn producers. Another benefit to late application is the reduced risk of N loss and increased likelihood of N availability when the corn crop needs it most. This Crop Insights will discuss evaluating N losses, best practices for rescue N applications and expected corn response. Prior articles in this N-management series have discussed N rates (Shanahan, 2011) and N timing (Butzen, 2011).
Another way to estimate whether a rescue N application is needed is to use the Nitrogen Loss Scoresheet developed at the University of Missouri (Scharf, 2008). After estimating the amount of nitrate lost by either method above, a better decision can be made as to whether a rescue N application is needed and how much additional N is required.
1 The author gratefully acknowledges John Shanahan and Wade Givens for providing the precipitation map (Figure 1).