Cover crops are usually touted for their contributions to soil health. But for no-tillers with livestock, covers can provide an immediate benefit to the bottom line by also serving as forage.
The key to dual-purposing cover crops for both soil-building benefits and forage is to strike a balance between the objectives of both uses, says Penn State soil management specialist Sjoerd Duiker.
“I think we have a great opportunity to restore that marriage between the livestock and crops,” Duiker told attendees at the 2013 National No-Tillage Conference.
Perhaps the most important factor in using cover crops as forage is evaluating the crops that no-tillers produce for profit. No-tillers raising corn have three windows for cover-crop establishment, Duiker says: after early corn-grain harvest, after corn silage or after another crop prior to planting corn.
Duiker warns that seeding cover crops prior to early-planted corn can be a challenge because the covers may not develop enough biomass before being terminated. But a farmer could let that cover crop grow longer in the spring, harvest it as forage and plant corn into the stubble, creating a double-cropping system of sorts.
Duiker says covers can be seeded before or after soybeans. The benefit of raising covers before soybeans is that soybeans are typically planted later than corn so the cover crop can develop more.
Covers can also be seeded after harvesting small grains or prior to planting sorghum, Sudangrass, millet, alfalfa or grass hay.
While Duiker acknowledges the popularity of corn in the U.S. for its productivity, he encourages no-tillers to consider adding alternative grain or forage crops to their rotation to allow for the introduction of different cover crops for forage.
“Corn also has some disadvantages. Nowadays, the cost of producing it is enormous compared to crops like sorghum or millet,” Duiker says.
Some no-tillers may shy away of an alternative like Sudangrass because its multiple cuttings require more work than corn silage, he says. A one-harvest alternative to Sudangrass is forage sorghum.
He says these crops aren’t only more cost-effective and productive for forage, they can also be established after the optimum corn-planting window to open up more choices for what’s possible with crop rotations.
Regardless of the main crops a no-tiller is raising, they will likely find a plethora of potential cover crops to use to meet forage needs.
Corn growers may consider using shade-tolerant covers interseeded into corn for overwintering. Duiker says a good choice is red clover with annual ryegrass.
“We need something that is very tolerant to shade because it just has to hang in there until our corn comes up,” he says.
Seeding oats after corn-silage harvest is another option. Duiker says that unlike winter wheat or cereal rye, oats don’t have to go through a cold period known as vernalization to begin producing a stem. When oats are planted in the late summer or early fall, they grow vigorously and can produce a lot more forage than rye or wheat.
“That creates the opportunity to have a harvest of forage there in the fall, and that forage has a very good feed value,” he says.
Winter-hardy cereals, grasses, legumes and other broadleaves can also be established after corn silage for spring harvest. Cover-crop mixes might work nicely here.
“We use mixtures because different species occupy different niches,” Duiker says. “They use light, temperature, water, nitrogen and phosphorus in different ways, and they have different pest and disease sensitivity. Try to have species that complement each other.”
A number of cover-crop mixes have been used, but Duiker says a mix of annual ryegrass and crimson clover is particularly popular. Both annual ryegrass and crimson clover have very small seeds and can be seeded at low rates, while costing only $2 per pound.
Duiker says these mixes can also provide very high food protein.
Multiple mixes grown after corn silage have been studied on farms in southeast Pennsylvania for forage quality. More than half had a relative feed value (RFV) greater than 110. Duiker says mixes above 100 RFV are excellent for dry cows and heifers, and reasonable for lactating cows.
For small-grain growers, Duiker says warm-season grasses, cereals, cool-season legumes and other broadleaves can be planted after winter wheat is harvested and then be harvested as fall silage.
Another choice is to harvest small grains for grain and follow it with double-cropped soybeans. Red clover can be frost-seeded into small grains for spring or fall harvest.
Duiker reminds no-tillers that cover crops aren’t just for feeding livestock, but for boosting soil health, protecting against erosion, breaking up compaction and managing nutrients.
Nutrient management can be heavily affected by cover crops, especially the nitrogen and phosphorus levels in the soil from livestock manure.
If a farmer is applying manure every year to meet the nitrogen needs of the corn, he will start building up very high levels of phosphorus, Duiker says.
He once saw soil analysis results of a farm that had levels of 1,000 ppm of phosphorus in the soil.
“You would think, ‘Oh, that’s good. I can grow crops in that field for 1,000 years, perhaps, without putting any fertilizer on.’ But it’s becoming an environmental problem,” Duiker says.
Incorporating other crops into a corn-heavy rotation is the best way to remedy this issue, he says.
For example, a corn-soybean or 4-year, corn-alfalfa rotation would level off that excessive phosphorus since manure wouldn’t need to be applied to those non-corn crops. This is because legumes are able to fix their own nitrogen, Duiker says.
“Because you’ve built up that the phosphorus in the years that you grew corn with your manure application, you don’t need to put any fertilizer on the legumes,” he says. “The key is to have a crop in rotation that fixes its own nitrogen.”
Caution On Manure
Avoiding manure applications on legumes also helps to manage weeds. Duiker says weeds thrive on the manure’s nitrogen, so skipping an application allows legumes to be more competitive and decreases weed problems.
Legumes can increase nitrogen available to the following corn crop. Studies in Landisville, Pa., in 2007 and 2008 showed corn yields fared better after hairy vetch, crimson clover and red clover cover crops, with varying nitrogen amounts added.
When no extra nitrogen was added, corn grown after crimson clover in the 2007 study did the best with a 60-bushel yield increase over corn with no prior cover crop.
“Crimson clover has been kind of our surprise,” Duiker says. “We thought it was not going to be winter hardy, but it has been doing very well.”
Hairy vetch also did well in the study, but not as well as crimson clover. Duiker adds that sometimes farmers will run into problems with hairy vetch, as it doesn’t always survive the winter.
“You have to plant hairy vetch in a timely manner,” Duiker says. “We’ve had success with planting these legumes after corn-silage harvest, but not after corn-grain harvest.”
Duiker explains that if hairy vetch or crimson clover is planted too late, they won’t be large enough to survive the winter. But if they are planted too early, they’ll become so lush they may still winterkill.
“When it becomes very tall and then gets hit with frost, all the aboveground material goes down,” he says. “I don’t know what’s going on. It suffocates everything underneath and the plant itself dies.”
A possible solution is to mow it before winter dormancy sets in, similar to recommendations for forages like annual ryegrass. He adds that it may not be possible with hairy vetch, due to its vines, but believes this would work well for crimson clover.
Frost-seeding red clover in the spring into standing winter wheat can also increase following corn yields. A study from 2007 in Landisville, Pa., showed higher corn yields after red clover, regardless of nitrogen applied.
Duiker says there’s also more potential to harvest or graze the red clover without negative effects for corn.
He says there will be a significant amount of biomass by October or November when farmers can safely harvest or graze the crop.
In spring, the red clover will regrow and provide excellent mulch cover for corn, sorghum, millet or Sudangrass.
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