The earlier wheat harvest in Illinois, along with good soil moisture, has some growers thinking about trying doublecrop soybeans farther north than usual this year, notes Emerson Nafziger, University of Illinois Extension agronomist.
"We have little data on planting soybeans this late in central Illinois, but with the good soybean price, it should take less than 10 bushels per acre to pay the cost of planting soybeans after wheat," he notes. "We think that the chances of yields of 10 bushels or more are good, but there's no certainty this will happen."
Nafziger reminds growers that doublecrop soybean varieties should not be earlier in maturity than full-season soybeans. Varietal maturity should not be increased as it sometimes is in southern Illinois, given the greater danger of frost coming before maturity farther north.
"It's better to plant DC soys in rows 20 inches apart or less, and seeding rates should be kept on the high side," he explains. "Soybeans planted this late do not typically grow very large, so they often benefit from having plants somewhat closer together."
The biggest dangers to doublecrop soybeans are hot, dry spells in August or September, and early frosts, which would end seed-filling well before it's complete.
However, if the crop can get off to a quick start, it should begin seedfilling by mid-August, and should be able, weather permitting, to fill a reasonable crop by late September.
"One advantage we have with doublecrop soybeans is the ability to wait to apply herbicide or to make other expenditures until we know something about crop prospects; if prospects are poor, we can cut our losses," he adds.
As is the practice in southern Illinois, narrow rows and slightly higher seeding rates should be used farther north, Nafziger reiterates.
For more information, check out the June 30 edition of The Bulletin, an online publication written by U of I Extension specialists in crop science, at http://ipm.illinois.edu/bulletin.