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Heat and Drought Stressing Iowa Soybeans

It is still very dry in our area of Iowa in the U.S. Midwest. The crops still look ok right now, but they are on the verge of being in trouble. We got very little rain through July, and it has been hot, with temperatures approaching 37°C, or 100°F. This stress impacts everything on our farm.


Our soybeans are setting pods, but the question is how many of those pods will be aborted? Or how many of the pods will be dropped prematurely, without developing soybeans due to stress. We need moisture to make a crop. The crop still looks ok, but on the tops of hills, the soybeans are starting to show stress, turning gray and losing color. We are also starting to see some insect pressure in the soybeans, like the Japanese beetle in this photo, so we are keeping a close eye on them.

Our corn pollinated well, but under stress, the ears will start tipping back, meaning that kernels at the end of the cob stop forming and filling out. We have been applying fungicide on corn to protect plant health. We have found that we consistently can improve yields by applying a fungicide. We apply this fungicide ourselves with a sprayer that sits above the corn crop on narrow wheels. We have been treating more than 404 hectares, or 1,000 acres, of our corn. We have also been treating another 1,210 hectares, or 3,000 acres, of corn for other farmers in our area.


During the first couple weeks of August, we will decide if we should apply any fungicide to our soybeans. If we get enough moisture that the crop will likely survive and produce a reasonable yield, we will consider applying fungicide to support plant health. We haven’t seen a consistent yield improvement when treating soybeans with fungicide the way we have seen it in corn. But because the plants are under so much stress, a treatment may give them a better chance. In the past, we have treated soybean fields with hail damage, because they need help to handle additional stress. Like with many decisions this season, what we do will depend on the weather.

The heat has also been hard on our pigs. They now weigh between 110 and 125 kg, or 250 and 280 pounds. They will start going to market in mid-August. But this group has had health struggles that we have been helping them fight as they grow. The heat stress makes it harder for them to stay healthy.

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