Rains during June and July set new records in some areas of the Cornbelt this year, causing weak root development, nitrogen loss and even affected pollination in some fields with poor ear-tip fills. Leaf diseases like Northern Corn Leaf Blight and Gray Leaf Spot were rampant in some areas causing additional stress on the corn crop. Some of the effects of this stressful environment on grain-fill are indicated below:
• After pollination, we need 50-60 days depending on the relative maturity of the hybrid, for the grain-filled period. This is when the plants’ primary focus is to fully develop the kernels.
• If there is severe heat or moisture stress during the grain-fill period, the plants start to cannibalize their leaves and stalks to fulfill the growing needs of their progeny, the seeds or grain.
• Plants, like animals, don’t want to produce runts. So, if there is stress during the grain-fill period, the plants start to abort the youngest kernels causing tip die-backs so that the remaining kernels can fully develop.
• Foliar fungicides are most effective if sprayed after the pollination and ovule fertilization has completed. Leaves above the ear contribute the most to grain yield; so it’s important to keep them healthy and disease-free during the grain-fill period.
• The physiologic maturity or black layer occurs at about 32-35% grain moisture. Stress before this period can cause kernel abortion and light test weight.
•If the plants have diverted the nutrients from the stalks to “feed” the grain, it can lead to pre-mature death and susceptibility to stalk rot organisms. We need to scout the fields, check them for stalk rots during September and plan on which fields to harvest first.