Ken Albrecht was optimistic that growing climbing beans with corn would increase silage yield and protein content. It looked like a good way for Wisconsin dairymen to cut feed costs.
But now he's not sure.
“It seemed like it was going to be a very useful system,” says Albrecht, a University of Wisconsin agronomist. “But based on our results, it may not be worth the extra trouble.”
In two years of research at two locations, he and graduate research assistant Kevin Armstrong grew corn with three species of climbing beans: lablab, velvet bean and scarlet runner. In each case, the beans were planted 6” from the corn rows two to four weeks after the corn was planted.
“The idea was, the corn would develop without a lot of competition,” says Albrecht. “Then later, as the season progressed, the beans would climb the stalks and we'd have that additional yield as well as extra protein.”
But none of the beans significantly increased silage yield. In most cases, yields of corn-bean mixtures were equal to, or slightly lower than, those of corn alone.
Protein was almost always higher, but only by one percentage point. The difference was small because the bean forage wasn't as high in protein as expected, testing 13-15%. The beans matured slowly and hadn't formed pods when the corn reached maturity.
The higher silage protein was offset by slightly lower energy. Still, Albrecht calculated that corn-bean silage could be worth about $50/acre more than straight corn silage when fed to dairy cows.
Initially, he was excited about scarlet runner beans. He saw them growing with corn in higher elevations of Ecuador, and thought they would be a good fit for the northern U.S. But they're susceptible to white mold and potato leafhoppers, and contributed little forage to the silage mixture in these trials.
Lablab looked the best. It consistently increased silage protein and showed a tendency to increase yield. He thinks a corn-lablab partnership could be a paying proposition for growers — if the two crops were planted at the same time and lablab seed could be purchased for a reasonable price.
He planted the crops separately to prevent the beans from getting ahead, but now believes that's not necessary.
“If I was going to do this on a commercial scale, I would plant 15” rows with alternating rows of corn and beans,” he says.
Lablab is grown for forage and grain in Australia. But here it's used mostly in wildlife food plots, and the seed costs around $2/lb. Albrecht and Armstrong planted 23 lbs/acre. At that rate, the added seed cost of a corn-lablab mixture would negate most of the $50/acre gain in feed value. So the price would have to come down for this to be feasible.
Growing corn and soybeans together is another option. The Roundup Ready trait in both crops solves the herbicide compatibility problem faced by growers who tried it in the past. But researchers have found that corn-soybean mixtures don't yield as much forage as corn alone.
Planting corn and soybeans in strips and mixing them with the chopper works fairly well. If maturities are matched, the soybeans have filled pods at harvest and their protein can equal that of alfalfa.
But timing the harvest so the soybeans aren't too mature, yet the mixture is dry enough for proper ensiling, can be tricky, says Albrecht.
“With climbing beans, it's not much of a challenge,” he says. “They might be easier to work with.”
Corn-Sorghum Mix Cuts Drought Risk
Worried that drought will hurt your corn silage yields next year? Reduce potential loss by planting forage sorghum with corn, suggests Bruce Anderson, University of Nebraska extension forage agronomist.
You can replace 25-50% of corn seed with sorghum seed, depending on feed quality needs and the weather outlook, he says. Normally, total silage yield will be about the same as with straight corn silage, and the amount of sorghum in the mix will be roughly proportional to that planted.
“In a dry year, a higher proportion of the silage will be forage sorghum,” says Anderson.
A few Nebraska growers have planted corn-sorghum blends with fairly good results, he says. They work better for beef cattle than for dairy, because the silage isn't quite as high in quality as straight corn silage.
“You're focusing more on tonnage than on overall quality,” he says.
The biggest challenge may be in setting up planting equipment, especially if you want to plant the two crops in the same rows. Heavy, round sorghum seed tends to settle to the bottom when mixed with corn seed.
Planting them in alternate rows may be easier. But that can be tricky, too, if you're using an air planter with a single hopper.
“It's just an idea for people to consider,” says Anderson. “It probably was more valuable 20 years ago, because corn breeders have made good progress in developing hybrids that can handle dry periods for more extended time periods than they used to.”