Intensive Soybean Management

Can we find ways to increase soybean yields through intensive management? Can we increase the use of insecticides and seed fungicides to economically increase the yields? What about yield spacing and variety selection?Bruce Potter, U of MN integrated pest management specialist has been conducting trials in Southwest and Northwest MN to determine how to achieve maximum soybean yields. When selecting seed, full season varieties often yield higher, but it is advisable to plant a mix of adapted maturities and avoid back to back varieties. Another item on the list is row spacing. “The narrower the row spacing the better,” says Potter. “That doesn’t mean the 30” row will yield less than a 10” row, but they very seldom yield more.” He does caution against going below 10” row spacing because of emergence issues. “The yield potential will go up, but that can be overrun by bad planting conditions and poor seed placement,” he warns.

Planting date is another hot topic, and Potter advises getting into the ground as soon as possible, with a little common sense. “If you can plant May 1, but a snowstorm is forecasted for May 2, you may want to wait,” he advises. If the soil temperature is cool, the soybeans aren’t going to grow, but at the same time, it will be too cool for the pathogens to work. “If you get those plants in early and they get out of the ground, even though you’ll lose a little bit of stand, they more than make up for it in growth,” says Potter.

For seed fungicides, Potter is little more reluctant to use them for three reasons: First of all, they don’t last very long, probably about 10 days, and if unfavorable conditions exist after that time frame you will still have problems. Secondly, most fungicides are a mix, but none of them are real broad spectrum. Just because you can control some of the pathogens on the plant in the early season doesn’t mean you can control all of them. And lastly, unless you lose enough plants that the soybean cannot compensate, you won’t see a yield difference anyway. Potter does advise considering a fungicide if you are going into wet soil, or if you have a history of stand problems.

A hot topic in recent years has been “insurance” pesticides, but Potter believes these create new problems. “After an insurance spray, when you have more aphids move into the fields, then you have issues with no beneficial [insects] to stop them,” says Potter. “Insurance foliar fungicide applications are the same, taking out the good with the bad.” Potter warns that if you are spraying aphids early, and you use the wrong product, you can flare other things, such as spider mites.

While fungicides and insecticides are needed in some years, the research has not shown that they are necessary every year. Intensive management of soybeans can lead to unintended consequences and expense. Manage your soybean fields on a year by year basis, and make decisions based