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Hardworking Annual Forages

Warm-season grass crops can fill a gap when others fail.

Warm-season annual grasses offer options for forage production in years when other hay crops are reduced.

With an eye on helping livestock producers choose a grass crop best suited to their needs, researchers at the University of Minnesota (UM) are evaluating several species of warm-season grasses.

These can potentially fill a production gap caused by unexpected winterkill of alfalfa in operations where corn silage or cash crops are not viable options for giving alfalfa fields a needed break before being reseeded to alfalfa.

“Replanting alfalfa right away shows very low success due to residual autotoxicity,” says M. Scott Wells, UM Extension forage and cropping system specialist. “It’s a good idea to take at least a year off from alfalfa to avoid autotoxicity. Warm-season annual forages can serve as valuable alternatives to fill this void and to make up for lost production.”

In an ongoing study, researchers are comparing yield and feed quality of several forages including annual ryegrass, annual ryegrass and red clover, BMR sorghum, millet, Italian ryegrass, sorghum Sudan grass, and teff.

The forages are no-till and seeded in late May when the soil temperature is about 60°F. The fields have previously grown alfalfa terminated with glyphosate to simulate winterkill. For all forage species, the first cutting occurs 30 days after emergence. Two additional cuttings are taken at 30-day intervals.

Yield. “Teff and annual ryegrass have produced the most,” says Wells. Both yielded about 4.5 tons of dry matter per acre, followed closely by annual ryegrass and red clover at 4 tons. Italian ryegrass and sorghum Sudan grass yielded the least at 3.8 tons of dry matter per acre.

The study is evaluating the potential nitrogen (N) credit from alfalfa and whether the warm-season grass benefits from additional N. “Our yields did go up slightly with the addition of N, but not enough to warrant the cost of the input,” says Wells.

Nutritive Value. The crude protein (CP) in the forages ranged from 9% to 14%, with Italian ryegrass having the highest CP. Sudan grass had the lowest.

Teff had 10% CP. Yet in another UM study, when teff was kept vegetative by grazing, its CP was 14%. Because teff is a leafy, fast-growing grass, Wells suggests that cutting it at shorter intervals to keep the plants vegetative at harvesting would yield forage with a CP approaching 14%.

Besides being high in CP, Italian ryegrass had 80% neutral detergent fiber (NDF) digestibility. Others tested 65% to 55% in NDF digestibility; Japanese millet had the lowest rating.

No surprise then that Italian ryegrass tested 160 in relative forage quality (RFQ), with all forages ranging from 110 to 160 in RFQ.

Among the forage species, teff stands out as a possible front-runner because of its good yield combined with relatively high nutritive quality, given timely harvesting.

Another draw for teff may be its ability to suppress weeds. “We observed that across all grasses, teff was the only one to hold back weeds,” says Wells. “We grew the teff in rows with a 7-inch spacing. Teff closes the canopy quickly and has a really fine rooting structure close to the ground surface.”

The millets suffered the worst from weeds.

“By evaluating these grasses, we hope to provide options for farmers, especially in years when a stand of alfalfa has winterkilled,” says Wells. “The information helps guide a choice of annual crops that may make a good fit with the other forage supplies that are available to producers.”

LEARN MORE

M. Scott Wells email at mswells@umn.edu

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