If it’s too late to plant corn for enough yield to make a profit, or to at least make more than crop insurance would pay if nothing was planted, does it make sense to plant soybeans instead?

“We have run our soybean planting-date studies into the first or second week of June, but we still have to project expected yields past the last date we actually planted,” Nafziger says. “As with corn, we would expect soybeans planted at the end of June or early in July to yield half what they would if planted early. This is about two weeks later than the normal double-crop planting date in southern Illinois."

Double-crop soybeans have averaged 72% of full-season soybean yields over the past 10 years at U of I’s Brownstown Agronomy Research Center, so using early July as the 50%-of-maximum-yield planting date seems reasonable, he adds.

“We know that double-crop (or very late-planted) soybean yields can range from zero to good, and there’s no way to predict, at planting, which end of this range they’ll be on,” Nafziger says. “As many found out in 2012, planting into bone-dry soils is not usually conducive to high double-crop soybean yields. And in northern and central Illinois, double-crop soybeans or soybeans planted (or replanted) in late June or early July have had a considerably lower rate of success than that of double-crop soybeans in southern Illinois.”

One important difference between double-crop soybeans and soybeans that are planted late but don’t follow wheat harvest is the available water left in the soil.

“Wheat removes a substantial amount of water from the soil as it matures, and in years with average June rainfall, the soybean crop that follows wheat has much less soil water available than does the crop that follows only the crop from the previous year,” Nafziger says. “As is always the case, good rainfall through the rest of the season can cancel out this advantage, but it won’t eliminate it averaged over years.”

A soybean crop planted in mid- to late June does not need to be managed differently than early-planted soybeans.

“Our recent research indicates that narrow rows tend to yield more regardless of planting date, and raising seeding rates seldom produces much advantage when planting late,” Nafziger explains. “Unless a late-maturing variety was the first choice for earlier planting, there is no advantage to changing to an earlier variety for late planting.”


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