Kentucky farmers monitored water use in corn as they dealt with hot, dry weather leading up to July.
Corn water use increases from emergence to about V15 where it peaks until about R2 (blister stage) and then starts to drop off after that, according to Chad Lee, University of Kentucky Extension grain specialist. When at its peak, corn uses 0.25-0.33 inches per day.
The amount of water loss depends on the air temperature, humidity and cloud cover. Corn that is pollinating is the most sensitive to water stress.
By July 1, 2021, 20% of Kentucky's corn crop was pollinating, but the 5-year average is 35% of corn pollinating by July 1. As corn planting started later this year, it predicted 15% or more of the Kentucky corn crop will pollinate within the upcoming weeks.
Strip-tilled fields may be at an advantage for holding moisture in the next few weeks because before corn is tall enough to cover the rows, soil may lose water. At this time, stripped-tilled fields have less evaporation.
Once the corn crop covers the rows, nearly all water loss is from the corn plants. It's called a transpiration, and at this point, the soil's residue cover becomes less important than when corn plants were smaller. Therefore, deep roots are crucial for corn crop.
Farmers who irrigate must keep a close eye on soil moisture and crop growth stages. Corn in the highest growth stages should be watered first, but don't overwater the crops. In addition, dry and saturated soil can damage corn pollination. For the best results, moisture sensors will detect how much irrigation should be applied.
For the farms without irrigation, heat and water stress depend on time. Corn close to pollination should be watched closely over the next 2 weeks, while corn in the early stages of growth isn't as vulnerable. If irrigation isn't an option, farmers should consistently monitor their fields and pollination.