Trey Koger, Syngenta crop expert, whose primary territory includes the mid South, says that late Group IV to early to mid Group V soybean varieties are recommended for double cropping. Most soybean seed is treated with a fungicide and more growers are using seed treated with an insecticide for early-season protection. “We recommend seed treatments for both full-season and double cropping situations,” Kroger says.
Much of double cropping is done in nonirrigated environments, so if growers follow winter wheat with soybeans, they need moisture to get the soybeans established. Soybeans will not generally yield as well as a full-season crop, but when prices are as high as they have been, more growers are willing to sacrifice yield.
Similarly, yields will generally be lower for late-planted corn, but a winter wheat crop can reduce the amount of supplemental nitrogen needed for the corn by as much as 40%, Koger says.
Another benefit of a double crop system is the potential use of additional herbicide modes of action in one of the two crops that otherwise may not be options in a single crop system. Other modes of action can potentially prevent or manage herbicide-resistant weeds.
Growers considering double cropping should do soil testing to get a handle on fertility levels across fields and to better manage their fertilization programs, says Scott Eversgerd, Pioneer Hi-Bred, a DuPont business, whose territory is southern Illinois (south of I-64 from St. Louis west to Indiana in the east). “You want to make sure you’re replacing nutrients,” he says. “You don’t want to go negative in nutrient levels.”
Soft red winter wheat is frequently followed by soybeans in Eversgerd’s territory, but a few farmers are experimenting with winter radishes followed by corn. In these areas with heavy clay pan soils, corn roots can more easily grow down the areas where radish roots had been. Shattering of the pan creates a better scenario for corn rooting, which is a benefit of double cropping, Eversgerd says. However, it can be difficult to get the winter crop established in the fall, he adds.
Growers need to kill the winter radish with a burndown herbicide in the spring. This residue creates an environment for disease, but the advantages of double cropping tend to outweigh the disadvantages, Eversgerd says. He recommends selecting varieties or hybrids with a good defensive package. “We’re still learning about specific diseases, but Pythium and Rhizoctonia can hurt the establishment,” he says.