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June 21, 2018

High Temps last Weekend probably did not cause Many Problems

Author: Michael Cordonnier/Soybean & Corn Advisor, Inc.

There were record high temperatures registered this past weekend in the central United States including some record high nighttime temperatures as well. I do not see these temperatures as a major problem for corn at this stage of the crop development unless the crop was suffering moisture stress. Probably the greatest harm caused by the high temperatures was a depletion of the soil moisture, but there are more showers in the forecast for this week.

Extra warm night temperatures can be a concern for corn, but mainly if they occur after the corn has pollinated and it is into grain filling. When the low temperature at night exceeds 72-73-74°F the corn plant can have higher levels of "dark respiration." If it is too warm at night, the plant spends extra energy maintaining cellular activity at night instead of using that energy to fill the kernels. One or two extra warm nights are not a concern, but it these temperatures are repeated over a longer period of time, they can negatively impact the corn yield.

These yield losses are generally the result of smaller and lighter kernels than expected, but the lower yields are hidden from view until the crop is harvested. These type of losses are generally not excessive, but they can trim the corn yield. Corn likes cooler temperatures at night. The cool nighttime temperatures registered last August is one of the reason why I think the U.S. corn yields were so good in 2017.

Excessive dark respiration can be a problem for corn, but it is not a problem for soybeans because of the nature of the plant. High temperatures and abundant rainfall can result in excessive vegetative growth of soybean plants. The plant puts too much energy into making a large plant when some of that energy could go toward filling pods. A little bit of dry weather earlier in the growing season is not necessarily a bad thing for soybeans.