COLUMBUS, Ohio - Ohio and Indiana farmers who practice relay intercropping of soybeans and wheat can choose from an array of wheat varieties that perform well in wider-row spacing, saving on equipment and seed costs.
Wheat row spacing normally is 7.5 inches wide, said Jim Beuerlein, Ohio State University agronomist. But in studies conducted by Beuerlein and Purdue University agronomist Tony Vyn, certain wheat varieties performed just as well when row spacing was widened to 15 inches.
About two dozen wheat varieties were analyzed for their performance in Ohio and Indiana.
"The purpose of making the rows wider than normal is for the machinery to get through, so you can get more light coming down into the canopy to help the soybeans grow," Beuerlein said.
Beuerlein and Vyn grew wheat varieties in both 7.5- and 15-inch row spacings, and compared yield, test weight and a variety of agronomic characteristics such as height and heading date. Beuerlein found that varieties that perform well in wide rows tend to be either tall by nature or grow tall because of favorable weather; and exhibit a nonerect growth habit that compensates for skips in the row or low population.
The research showed that wheat normally grown in 15-inch rows produces 5 percent to 15 percent less yield than wheat grown in 7.5-inch rows, but the lower yield from wide rows is partially offset by reduced seed costs, Beuerlein said.
"When growing wheat in 15-inch rows, a farmer only has to use half as much seed per acre," Beuerlein said.
"So, for example, if a 7.5-inch row has a two-bushel seeding rate, the farmer has saved one bushel at $12 a bushel for seed. He may lose four bushels of grain in yield, but at a grain cost of $3 per bushel he can still make the same profit. One bushel of seed has the same value as four bushels of grain." Seeding rates are significantly lower in 15-inch rows, Vyn said. He added that plants in the wider rows appear to be somewhat shorter than wheat in narrower rows.
"We observed that it is important to keep seeding rates at 850,000 seeds per acre in 15-inch rows," Vyn said. "That's much less than the traditional seeding rate in 7.5-inch rows of 1.3 million to 1.5 million seeds an acre.
"We also found that wide-row wheat is less likely to lodge even with high nitrogen fertilizer rates." Wider-row spacing saves on equipment costs, because fewer seed meter units are necessary on the drill, Beuerlein said.
"Farmers are looking for anything that will reduce production costs," Beuerlein said.
The relay intercropping process usually involves planting wheat in October, then interplanting soybeans the following year in late May or early June. Even earlier soybean planting dates are possible with polymer-coated seeds that delay soybean emergence.
The OSU-Purdue data indicates both crops in an intercropping system perform well.
"In many ways we are not sacrificing wheat yields in order to gain the potential of 30-bushel-an-acre relay soybean yields in areas that are traditionally not suited for double-crop beans," Vyn said.
Results of the study are available at Ohio State Extension's Crop Observation and Recommendation Network (C.O.R.N.) newsletter Web site. It is located online at http://www.ag.ohio-state.edu/~corn/archive/2001/sep/01-30.html.