Shenandoah Valley Farmers Learn Benefits of Cover Crop Mixes

11/17/2012 7:00 AM
By Andrew Jenner Virginia Correspondent

TENTH LEGION, Va. — Several dozen people attended a cover crops field day in northern Rockingham County last week to learn more about the latest ideas for cover crops and other management techniques shown to improve crop yields and quality in the Shenandoah Valley.

Sponsored by the NRCS, Virginia Cooperative Extension and the Shenandoah Valley Soil and Water Conservation District, the event included a series of presentations and test plot tours led by NRCS, Extension and Virginia Tech experts.

One lesson emphasized by NRCS agronomist Richard Fitzgerald was the benefit of cover crop mixtures rather than monocultures.

“The soil biologists are telling us diversity is the key to improving what’s going on beneath the ground,” said Fitzgerald, who showed participants the results of yield trials he conducted this year on Mike Phillips’ farm (Phillips is also an NRCS technician).

Using a cover crop blend planted at per-acre rates of one and a half bushels of triticale, 10 pounds of hairy vetch and eight pounds of Austrian winter peas, Fitzgerald and Phillips recorded a 29 bushel-per-acre yield increase for corn over a control field with no cover crop.

Another plot, treated only with fertilizer, showed a yield increase over the control plot, but one not nearly as high as the mixed cover crop plot.

Finally, Fitzgerald said, adding nitrogen to a plot that had been planted with the cover crop mixture showed no yield increase, indicating that cover crop mixtures alone can maximize corn yields.

During the field day, Fitzgerald also discussed rolling cover crops to kill them, and planting directly through the plant material that remains atop the soil like mulch.

While it’s a technique typically associated with organic production, Fitzgerald says conventional producers can also realize substantial benefits from rolling.

“That’s consistently our highest yielding corn,” he said, adding that farmers he’s worked with have reported no problems with planting or emergence through the dead cover crop and have seen yield increases over 20 percent.

“When you start talking about a 25-percent increase, that’s a big deal,” Fitzgerald said.

Virginia Tech professor Rory Maguire and a graduate assistant, Stephanie Kulesza, also spoke at the field day about their efforts to perfect a litter injector that they hope will allow farmers to operate more profitably while minimizing nutrient runoff.

Their prototype litter injector, built by BBI, uses augurs to break apart chunks of litter and a system of chutes and discs to deposit the litter into slits in the soil that close behind the machine.

Maguire noted that while the machine shows promise, a number of engineering challenges are yet to be overcome.

“It’s not quite at the place yet where I’d say, Go out and buy one,’ “ he said. “We’re about 80 percent of the way there.”

Nevertheless, the technique, Maguire said, appears to capture about 20 percent more nitrogen in the soil compared to spreading the same amount of litter on the surface, much of that due to reduced volatilization of ammonia.

By placing the litter beneath the soil, injection also protects the litter from running off fields during a rainstorm.

At the event, Kulesza presented the results of field trials conducted on cornfields and orchardgrass stands this year to compare litter injection with surface application.

While no yield improvements were recorded, orchardgrass from injected stands contained significantly higher levels of protein when identical amounts of litter were injected or land-applied. The tests also showed equivalent protein levels when litter was injected at half the rate of land application, showing that injection could give a farmer the same forage quality with half the litter input.

Injected cornfields also showed significantly higher pre-sidedress soil nitrate test (PSNT) levels than fields where litter had been surface applied, although weather conditions this year ultimately damaged the corn in the test plots.

Kulesza told the audience that the results indicate that injection could represent a good opportunity for farmers once the technology has been perfected.

Fitzgerald said the large turnout and interest in the field day tells him the ongoing research that was discussed is providing farmers in the region with good information about ways they may incorporate new techniques into their management programs.

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