Experts Pit Cover Crops Against Winter Forage Crops

12/14/2013 7:00 AM
By Jessica Rose Spangler Reporter

MIFFLINBURG, Pa. — The idea of planting a cover crop during the winter months isn’t a new one. But talk to a dairy or livestock producer, and you’ll often hear them say that cover crops are a good idea, but the timing is a challenge.

Using the fields for feed production year-round can prove to be a game of beating Mother Nature out to the field.

Those topics — cover crops and alternate forage programs for dairy and livestock producers — were discussed at a Dec. 10 workshop by Penn State Extension specialists Sjoerd Duiker, Marvin Hall and Chris Houser.

Duiker’s presentation, “Cover Crops to Make Your System Tick,” included the hows and whys of planting cover crops in the first place.

Hall didn’t disagree with Duiker, but said he would rather the cover crops be used as winter forage instead of being killed.

Houser didn’t mind which method a producer uses, but reviewed how the Penn State interseeder can help combat Mother Nature’s tricky fall weather patterns.

Cover crops — or winter forage — are part of what Duiker calls a sustainable cropping system. By using continuous no-till, there’s a quick turnaround of crops in the field. Soil should be covered at all times with mulch or living vegetation, which is needed because more than 50 percent of Pennsylvania’s land is considered highly erodible, he said.

Duiker and Hall both cited multiple other reasons to use cover crops, including improving soil quality and ultimately improving yields.

Pennsylvania producers often think of rye as the dominant winter cover crop. However, Duiker, Hall and Houser agreed that numerous other crops and mixes can be used effectively.

Cover crops don’t always have to be seeded in the fall either.

“Crimson clover and hairy vetch can be established after early corn silage or small grain harvest in July and August,” Duiker said. “Red clover and yellow sweet clover can be frost-seeded in February or March into wheat or barley.”

When used in this method, red clover can also be harvested as forage in the fall or left to regrow over the winter to be killed in the spring and replaced with a planting of corn.

“Without a cover crop, corn yield was up to only 130 bushes per acres with 150 pounds of added nitrogen” per acre, Duiker said. When hairy vetch was used, “fields had up to 170 bushes in the first year. In the second year, it was up to 190 bushels.”

When crimson clover was used as a cover crop at the Rock Springs, Pa., research fields, the following year’s corn yield was not as good as the hairy vetch fields. But at the Landsville, Pa., test fields, crimson clover performed better.

Duiker said he believes this is because after the clover was killed and left as mulch in the cornfield, it helped to retain ground moisture in an otherwise drier soil than at Rock Springs.

When designing a cover crop mix, two species are usually selected that complement each other — fall versus spring growth, light and nutrient usage, plant varieties and their production in a producer’s particular area, etc.

Rye is not often used in cover crop mixes because it grows so aggressively that it typically drowns out the other crop.

Planting dates are critical. Over the three years of this trial, planting dates ranged from Sept. 7 to Oct. 7.

“If you have your own equipment, plant the cover crop the same day you take off corn silage,” Duiker said.

One surprising finding was that crimson clover performed much better than expected. Originally thought not to be winter hardy, these fields often grew better than hairy vetch, opposite from what had been anticipated.

Crimson clover’s seeding rate is also about half as expensive as hairy vetch, Duiker said.

If crimson clover/oat mixes are planted early enough in the fall, the oats can be harvested in the fall and the clover in the spring.

If crimson clover/ryegrass mixes are planted in September, good quality forage can be harvested at up to 3 tons of dry matter per acre in the spring, Duiker said.

The catch with that mix is that manure should not be applied. Otherwise, the ryegrass will grow too quickly and drown out the clover. Tonnage losses without manure are almost nonexistent, he said.

Keeping Duiker happy, Hall stressed that if producers are capable of taking a cover crop off as a winter forage crop, they’ve only benefited from all the time, money and effort used to plant the cover crop in the first place.

In a 2012 study that Hall cited, 17 varieties of annual ryegrass were planted and harvested three times before double-cropping with soybeans. The overall average total was 5.62 tons of dry matter per acre.

The best performing test plot was the Barherta Italian ryegrass variety with 6.08 tons of dry matter per acre.

When annual ryegrasses were single-cut before spring planting in 2013, the Barprisma Italian ryegrass came out on top with 1.77 tons of dry matter per acre.

When looking at one-cutting cereal varieties in 2012, the Trical 141 tritical variety gave the highest yield at 3.24 tons of dry matter per acre. In 2013, the Trical 141 came in second with a total of 2.98 tons. Huron rye was first with 3.07 tons per acre.

Cover crop blends gave some of the highest yields in the 2012 tests that Hall cited. The Italian ryegrass/clover King’s Mix and Triticale Plus —triticale 815 at 66 percent plus 33 percent annual ryegrass — each gave 6.53 tons of dry matter per acre after three cuttings.

In 2013, the mixes still performed well, but were not nearly as productive as the previous year. The top producer was Pocono — a Fridge/RootMax/radish/crimson clover mix — at 4.50 tons.

By simply taking the RootMax out of the Pocono mix, creating Charlotte, that test plot produced only 2.08 tons off one cutting, placing last.

All this data is useful, but not to the farmer who grows grain corn and doesn’t have a large enough window to plant a cover crop before winter. That’s where Penn State’s interseeder comes into play.

The interseeder is a machine designed to drive through a field of standing corn or soybeans, plant a cover crop, apply nitrogen and spray an herbicide all at the same time.

According to Extension agronomist Chris Houser, the interseeder is run through a cornfield at the six- to eight-leaf stage, typically the last week of June or the first week of July.

Clover is a cover crop that tends to perform well, according to Houser, because it can survive in low light and low moisture under the corn canopy.

In a trial, a fall harvest of the clover provided 700 pounds of dry matter per acre. The following spring, the same crop yielded 1,500 pounds of dry matter.

So far, all the trials conducted with the interseeder have shown no significant corn yield differences in the same year the cover crop was planted, Houser said. Trials have shown improved corn yields in year two for the same reasons Duiker cited earlier.

Without divulging all the details, Houser noted that commercial development of interseeder models is under way and the equipment may be available for consumers to purchase early in 2014.

Low Lignin Alfalfa

Hall briefly mentioned that people can expect to see a low lignin alfalfa on the market in the summer or fall of 2014.

This product is genetically modified to have a lower lignin content, therefore increasing the plants’ NDF (neutral detergent fiber) digestibility. Although it cannot be officially marketed this way, this product is projected to be 10 percent more digestible than the alfalfa plants currently being used, Hall said.

Lignin is one of three parts to a cell wall, the other two being cellulose and hemicellulose. Lignin is the only one of these three that is not digestible in the rumen. But in the “traditional” alfalfa plants that are currently on the market, lignin intertwines with the cellulose and hemicellulose, making it nearly impossible to be digested.

The new low lignin alfalfa will have a modified cell wall structure, allowing the rumen microbes to access the cellulose and hemicellulose more easily, therefore allowing more of the alfalfa plant to be digested and utilized.

Because of this new design, low lignin alfalfa should be harvested when almost flowering, versus the bud stage when traditional alfalfa should be harvested.

By doing this, a producer can make fewer trips across the field for the same tonnage, ultimately decreasing the costs of harvest.

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