We can plant on the optimum date, fertilize exactly as our soil test recommends, have perfect pest control…and then, Bam! We get whacked with a heat wave or drought period during corn pollination. As the corn crop progresses through its development, it is emotionally painful for a grower to witness corn leaves rolling during any growth period. However, pollination and fertilization are the most critical times for the corn to not exhibit stress.
According to Bob Nielson, Extension Corn Specialist at Purdue University, there is good news. Even in high temperatures, corn will not be stressed severely if soil moisture is adequate. Heat stress alone will not severely impact yield. Corn will enter the period of grain yield determination about 2 weeks prior to silk emergence.
If corn is wilting continually due to drought stress, it can decrease yield 3-4% per day. During silking and pollen shed, this stress can result in an 8% decrease in yield. Two weeks following silking can see reductions in yield up to 6% per day if drought stress is present.
If you see visible signs of stress in your fields, it may be from compaction during the wet spring and planting into “less than ideal” conditions. Shallow root systems will lack the ability to gather soil moisture and will show signs of moisture stress earlier than those with deeply developed root systems.
For more information on moisture and drought stress, read “Drought and Heat Stress Effects on Corn Pollination” written by Bob Nielson at Purdue University.