Seeding cover crops after corn silage makes sense for a number of reasons, says Sjoerd Duiker, Pennsylvania State University Extension soil scientist.
Crops like rye, oats, ryegrasses and clovers help reduce erosion, take up soil nutrients and improve soil structure by breaking up compaction. Their roots and plant residue increase organic matter, and they suppress weeds, especially winter annuals. Finally, cover crops can be used to feed livestock in winter grazings, or fall or spring harvests.
Duiker recommends drilling or seeding as soon after silage harvest as possible. “We have learned that timing is everything when it comes to cover crops. A lag of two weeks can make a huge difference in cover crop growth in our Pennsylvania climate.” He has studied, since 2010, several different cover crops, drilled after corn silage on Pennsylvania dairy farms.
Cereal rye. “This is really our true and tried crop that is virtually fireproof. It can be established in all of Pennsylvania after corn silage harvest, even into late October, and still successfully survive the winter,” Duiker says. The crop can produce very good silage in spring if harvested at the right time. Feed quality will decline if it’s harvested after soft dough stage. It should be seeded at about 2 bu/acre.
In his trials, the variety Aroostock was very winterhardy and produced a lot of biomass. Huron was a variety that yielded less biomass but had a wider window for a high-quality spring harvest.
Rye and oat mix. It’s too late this season, because the mix should be seeded at 1.5 bu/acre rye and 2.5 bu/acre oats immediately after harvesting August silage. It produces a high amount of biomass in fall and spring.
“In the southern parts of our state, a lower rate of rye might be combined with a higher rate of oats for high quality and tonnage forage production in the fall. The rye guarantees living cover in the spring.”
Annual ryegrass and crimson clover. Seeded at 10 lbs/acre ryegrass to 15 lbs/acre clover, this mix offers high-quality forage in spring.
“Because it includes a legume, it does not need high rates of manure application to flourish. The legume supplies N (nitrogen) to the ryegrass,” he says. Select winterhardy varieties and plant as early after silage harvest as possible. If grown taller than 8" before December, mow the cover crop to 3-4" tall to guarantee winter survival.
Triticale and crimson clover. Triticale, a wheat and cereal rye hybrid, should be seeded at 84 lbs/acre; crimsom clover at 15 lbs/acre. The clover doesn’t grow as fast as rye in fall. But it can produce high tonnage in spring and a wider harvesting window than cereal rye for high-quality forage. “When mixed with crimson clover, it even makes a higher protein mix,” Duiker notes.
Mixes with forage radish. Consider several possibilities, like radish-vetch-rye, seeded at 3, 10 and 84 lbs/acre, respectively; crimson clover and radish, at 15 and 3 lbs/acre; or radish-ryegrass at 3 and 10 lbs/acre.
“In our trials, the September plantings were typically too late to see much radish growth after corn silage, so the earlier it can be established the better. We noted the radish flourished in high-fertility situations with manure.”
Duiker says the cover crop becomes “less attractive” in the state’s northern areas or where corn silage is harvested late. “Whatever you do, don't plant radish alone or your soil will be completely bare in the spring. The radish plant dies around the year's end and the residue decomposes extremely fast.”
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