Maintaining grass and legume pastures as well as hay fields are important management factors for feeding beef cattle, says Frank Wardynski, Michigan State University Extension.
Generally, this is because legumes often contain lower fiber content with slightly higher energy and protein values than grasses. Consequently, cattle must consume more grass forage to attain the same quantities of energy and protein as compared to legume forages.
Another benefit of maintaining legumes in a mixed forage stand comes from their ability to fix nitrogen.
Bacteria at the roots of legumes convert atmospheric nitrogen into ammonia nitrogen for fertilization of the legume plant. Nitrogen then becomes available to the grasses as root and aerial portions of the legume plants die and decompose into the soil.
In pasture situations, animals consuming the legume plants will release nitrogen in urine and manure to feed the grass plants.
Many beef producers who have seen the benefits of legumes plant a mixture of grass and legumes during hayfield establishment – but over time legumes can die out and become a lower percentage of the forage stand, Wardynski says.
To keep hayfields and pastures in top shape, he recommends that legumes should make up 40-60% of the forage stand.
For hay production, the top portion of the plant is removed from the field along with the contained nitrogen. Therefore, they should contain legume percentages closer to 60% to compensate for the lost nitrogen.
Pasture systems, which allow for more recycling of nutrients as nitrogen is excreted back onto the fields in the form of manure and urine, should have closer to 40% legumes.
To maintain or increase your legume stand, Wardynski says frost seeding is a common and economical method. Management of the forage stand during the summer and fall before frost seeding is important to ensure there is little forage mat to allow seeds to obtain soil contact.
Late season grazing or cutting will prevent forage mat formation, he says, noting it generally reduces the vigor of the existing plants, allowing new seedlings to better compete in the spring.