With soybean and wheat prices projected to remain high or go higher, many growers are looking to capitalize on both through double-cropping beans. Obtaining the best wheat-bean yields will require much more than just planting after the cereal grain is cut.
Growers should select the proper maturity in seed varieties, assure there is a sufficient soil moisture and proper fertilization and plant beans as quickly as possible, says Alan Blaine, Mississippi State University Extension agronomist.
Even though soybean yields will likely be 15-30% lower if they are double-cropped after wheat, bean prices at $10-plus/bu., along with $7-plus wheat, point to a boosted bottom line. Double-cropping both can help increase income, spread risks and reduce soil erosion by providing ground cover most of the year.
Blaine says the double-crop system may require harvesting wheat at higher moisture in order to plant beans before late June. And a later-maturing seed will be needed to squeeze the most out of a tighter growing season.
Harvesting wheat at 16-20% moisture requires artificial drying — an added expense — but it may allow planting soybeans five to seven days earlier,” Blaine says.
“Late-maturing varieties offer the advantage of extending the growth season to capitalize on some fall rains,” says Blaine, noting that the later beans could also face the cool weather risk. “In addition, later varieties usually grow taller to provide more competition with weeds. Glyphosate-resistant varieties will also help prevent weeds.”
Blaine says fertilization, mainly phosphorus (P) and potassium (K), is best accomplished by applying the recommended amount for both wheat and soybeans in the fall during wheat seedbed preparation.
“THIS IS A GOOD WAY to fertilize soybeans and eliminate the need for topdressing wheat with complete (N-P-K) fertilizers in the spring or applying the fertilizer after wheat harvest,” says Blaine.
He notes that when submitting soil samples for testing, growers should ask for a double-crop recommendation, adding that without a soil test, a rate of 80 lbs. P and 80 lbs. K should provide adequate fertilizer based on average crop removal.
Planting soybeans directly into wheat straw and stubble provides superior soil conservation, eliminates the hazard of burning and leaves straw mulch to conserve moisture and delay weed emergence.
However, it requires planter modifications and special weed control considerations. Blaine says leaving about an 8-in. stubble and chopping and spreading the straw are suggested for stubble planting.
“Also, planting soybeans at a slight angle can be beneficial in obtaining a soybean stand,” he says. “This minimizes hair-pinning of the wheat straw.”
In this no-till system, a planter equipped with some type of coulter is needed to slice through the residue and open the soil in front of the double-disk opener.
“Since no-till planting is often on hard or rough soil surfaces, a heavy-duty planter with down pressure applied to the planter units may be needed,” says Blaine.
DAN POSTON, MISSISSIPPI State soybean agronomist at Stoneville, notes that a key to successfully producing double-crop soybeans is timely pest management and irrigation.
“We can grow decent double-crop soybeans, especially with irrigation, but we have to remember to water and spray as necessary,” says Poston. “Insect pressure — especially from stinkbugs — is phenomenal in late-planted soybeans and you can't let a week go by without scouting,” says Poston.
He recommends budgeting at least one fungicide application and two to three insecticide applications for double-crop soybeans with good yield potential.
For Northern growers, “The soybean planting date is critical in determining productivity of the system,” says Jim Beuerlein, Ohio State University Extension agronomist. “At the time of wheat harvest, the potential soybean yield is decreasing by at least 1 bu./acre for each day planting is delayed. If planting cannot be completed by July 10, double-cropping should not be attempted (in much of the Corn Belt).”