Legume-fortified grass pastures help cattle gain weight more quickly and reduce annual fertilizer costs, preliminary University of Nebraska research shows.

"Livestock gains on legume pastures have substantially exceeded pure brome pastures fertilized with nitrogen," said Bruce Anderson, an Institute of Agriculture and Natural Resources forage scientist.

Yearling calves gained up to one-half pound more per day when grazing alfalfa, birdsfoot trefoil or kura clover interseeded into brome grass, compared with brome grass pastures fertilized with 50 pounds of nitrogen. Kura clover, a cousin of red clover, is relatively new to Nebraska.

Legumes' concentrated protein and lower fiber content speeds animal digestion, which means higher total nutrient concentration and faster weight gain, Anderson explained.

"We hope legumes will increase rates of gain per animal and per acre while lowering long-term costs of production by reducing the need for commercial nitrogen fertilizer," Anderson said.

Legumes eliminate the need for up to 50-60 pounds of nitrogen fertilizer annually per acre. Legumes fix nitrogen from the air through their root nodules to feed themselves and benefit surrounding plants. This relationship provides more diversity and helps stabilize the ecosystem, Anderson added.

The biggest challenge in adding legumes is planting and establishing them in early spring, when brome grass and other cool-season grasses are growing fastest.

"It's not so much effort as it is dedication and planning," Anderson noted.

Establishing legumes in pastures costs $15 to $60 per acre. Costs include drilling or broadcasting the seed, controlling existing grass while legumes are getting established, and seed that runs $5 to $25 per acre, depending on type. Another cost may be adding phosphorus for thrifty legume growth and lime to boost soil pH to 7.0. Phosphorus often needs to be added every few years afterward as well.

Anderson recently completed the second year of a 5-year study at NU's Agricultural Research and Development Center near Mead. Adding legumes to grass pastures isn't a new concept, but its popularity varies with the price of fertilizer and livestock, he said. Future data will reveal whether different grazing strategies that involve two, six or 36 pasture rotations affect legume longevity. Legumes must last 6 to 20 years to be cost-effective.

He'll also plant legumes with warm-season grasses such as big bluestem, Indian grass and switch grass, which grow fastest in June and July. Warm-season grasses are less competitive with legumes than their cool-season cousins, and precautions are needed so the legumes don't completely take over. Typically, too much legume grazing can lead to bloat, a potentially fatal digestive disorder, although that isn't a problem with birdsfoot trefoil.

Anderson expects legume and grass pastures to have the biggest potential in eastern, south and central Nebraska and in subirrigated or irrigated pastures because of better moisture conditions.

A grant from the Sampson Range and Pasture Management Endowment helped fund this research.

- Cheryl Alberts

Birdsfoot trefoil

Alfalfa

Preliminary research shows that interseeding brome grass with alfalfa, birdsfoot trefoil or kura clover, a cousin to red clover, increases the weight gain of yearling calves up to one-half pound per day.