Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu and Amy Shober, Extension Specialist – Nutrient Management and Environmental Quality, University of Delaware, ashober@udel.edu
With variable corn growth following our wet spring, you may be interested to know more about what may be going on in good and poor performing parts of your fields. While lack of nitrogen (N) has been a major reason for poor corn performance due to very wet conditions in May and early June, there are other nutrients that could be lacking and contributing to poor performance. Nitrogen, sulfur (S), and boron (B) are all potentially mobile in the soil and may have moved below the root zone, while manganese (Mn) can be more available for plant uptake when soils are saturated. Nutrients can also be antagonistic to each other during plant uptake. For example, plant uptake of the ammonium form of N can slow the uptake of Mg from the soil. So, any N applications made for crop recovery may have impacted plant uptake of other nutrients.
This may be a good season to evaluate mid-season fertility since corn was under duress, plus the results of corn leaf sample testing can help you plan for next year. When at least 50% of the ears are showing silk, sample the entire ear leaf from at least 15-20 plants and submit these samples for plant nutrient analysis. Choosing where in the field you sample depends on what you are looking for. To evaluate general field health, stay away from obviously distressed areas that show insect or equipment damage or small areas that show nutrient deficiencies. However, if the goal is to determine why there is an issue, take samples from both field “good” and “bad” areas of the field and label the samples as such when you submit them for testing. Be sure to gently clean any soil or dust off the leaves to prevent contamination of the tissue with soil material, which can skew results.
Once you get results of your tissue test back from the lab, compare the values to the sufficiency ranges in the following table. Any nutrient below these ranges is lacking and could prevent your crop from reaching maximum achievable yield. These are meant to be guides, and may not be accurate for all soil types and corn hybrids. Keep track of the area you sampled and match it to any soil samples or yield you obtain at the end of the season. This information may help plan for next year or whenever similar weather patterns arise.
(Campbell and Plank, 2000)