by Sally Colby
It’s been an interesting season for growing corn. While some farmers are bringing in record yields, others are lamenting a season that was simply too wet and cool. Once the ground is bare, what’s next? Some fields in which silage corn was grown will be planted immediately with a winter cover crop, but it isn’t too early to consider what the field will be used for the following spring.
“Alternative cover crops offer opportunities to diversify crop rotation systems,” said Charlie White, Penn State extension associate in sustainable agriculture. “These cover crops are planted later in the season — late summer after small grain harvest.” Another option is to harvest a winter cover crop and allow a legume more time to fix nitrogen, or to have an earlier planting date for cover crops in the fall to get them well-established.
Less common species such as sorghum sudangrass, cowpeas and radish afford more diversity in a crop rotation. In many cases, seed for some of the alternative cover crops costs less so there’s a higher economic return on marginal land. These forage crops are often more heat and drought tolerant, so they’re suitable for ground where corn silage hasn’t done well.
Dave Wilson of King’s Agriseeds says that sorghum sudangrass BMR (brown midrib) is one forage option that has higher digestibility. Non-BMR sorghum sudangrass is a hybrid of sorghum and sudangrass, usually drilled at 50 to 60 pounds/acre. The non-BMR is used as a cover crop and can be also be grown as biomass. The planting date should be when soil temperature is 60 degrees and rising, which is later than corn planting date.
Where does sudangrass fit in a rotation? “After a winter annual,” said Wilson. “A lot of farmers will grow triticale or triticale mixed with ryegrass. They’ll cut triticale as a forage, then the ryegrass with triticale as a second cutting. That puts them into May, then they can plant the sorghum sudangrass in June.”
The first cutting is ready about 30 to 35 days after planting. “Cut at about 5 to 6 inches tall for better regrowth,” said Wilson, “then come back in another 30 days and cut it again.” Each cutting yields 2.5 to 3.5 tons of dry matter, depending on moisture. Sorghum sudans grow more efficiently with ample nitrogen and moisture. Once established, they will go dormant if conditions are dry.
Wilson says that it’s important to plant deeply — about 1.5 to 2 inches deep. “We don’t want them shallow,” he said. “They can be planted into late June and July. If the top of the soil profile is too dry, it won’t germinate.” Planting sorghums may require ballast on the drill to provide sufficient weight to drill deeply.
Sudangrass is a sudangrass hybrid with has a smaller seed, and is drilled at 30 pounds/acre drilled. Similar to sorghum sudangrass, thinner stem, dries faster and can be used for dry hay. “Sorghum sudangrasses are too wet and would be used for baleage,” said Wilson. “Sudangrass can dry sufficiently for dry hay.”
Another option is forage sorghum (BMR) that is planted at 6 pounds/acre. “This goes in in 15 inch rows, planted with a corn special or soybean planter,” said Wilson. “We want to singulate the seed.” Forage sorghum is grown tall, between soft dough to boot stage, then cut for a one-time harvest. Wilson cautions farmers to harvest forage sorghum before the seed head becomes too hard and difficult to digest.
Many farmers have success with forage sorghum planted at 6 pounds/acre along with Barkant turnips at 5 pounds/acre. This affords more diversity. “We can put these in for summer grazing,” said Wilson. “The brassicas — rapes, radishes and turnips — are some of the few crops that will grow competitively under the canopy of forage sorghum. They can be grazed in 30 days. The cows first graze the forage sorghum or sorghum sudan, then graze the brassicas that grow lower. There’s good weed control.” Wilson says that brassicas are high in protein (around 20 percent) and have no lignin. It takes time for cows that have never grazed brassicas to develop a taste for them, but that comes easily. Grazing areas should be backfenced so that animals don’t trample uneaten forage. Brassicas can be planted in spring, summer or fall, and do well in forage mixes. However, they are too wet to be suitable for forage.
Teff is a summer annual from Ethiopia. It has a very small seed — smaller than timothy — and requires a well-prepared seedbed that is adequately packed prior to planting. “No-tilling teff can be a challenge,” said Wilson. “We just want to scratch the surface and get it in, not too deep. Farmers who plant teff want to be able to bounce a basketball off of the field surface.” Wilson added teff makes nice hay.
Other alternative forages include Sunn hemp, a tropical summer legume. Sunn hemp grows tall, requires cowpea or mung bean inoculant, and can be grazed or cut as forage when young. Cowpea, which is actually a bean, is another summer annual. Cowpeas can be grown as a summer cover crop and can be grazed or cut. Daikon radish can be used as a forage in spring or summer, or as a stockpiled forage or a cover crop.
by Sally Colby