Why Not Legumes?
With high fertilizer prices this year many producers are considering incorporating legumes into their fescue pastures this spring. But just how much benefit do forage producers really receive from adding legumes? After all, legume seed isn’t cheap. There are four basic benefits to adding legumes: forage yield, forage quality, nitrogen fixation, and closing the summer gap in forage production. Let’s take a look at each of these.
Figure 1 shows a two-year study conducted in Lexington, Ky., to measure total forage yield of a fescue-red clover mix vs. fescue alone plus various levels of nitrogen fertilizer.
The fescue-red clover mix with no nitrogen actually out-yielded the straight fescue that received 180 lbs. of additional nitrogen. But what about forage quality? A study from Alabama (Figure 2) found that a fescue-ladino clover mix with no additional nitrogen had higher palatability, intake, digestibility and nutrient content than straight fescue. The fescue-ladino mixture produced 582 lbs. of total beef per acre while the straight fescue plus 150 lbs. of nitrogen produced only 374 lbs. of beef. Individual rates of gain were over 40 percent higher (1.53 lb/day vs. 1.06) for the steers grazing the fescue-clover mix.
In addition, two more studies found that cows grazing a fescue-legume mix had significantly higher conception rates than their herd mates who grazed straight fescue.
Another major benefit of adding legumes to pastures is the production of nitrogen through a process known as nitrogen fixation. Once a stand reaches 30 percent clover and 70 percent grass it should be able to produce 75 lbs of N/acre/yr. If nitrogen is valued at $0.60/lb then that means the clover is producing approximately $45/acre in nitrogen fertilizer. Results will vary depending on the growing conditions during the year.
A benefit often overlooked of incorporating legumes is their ability to help fill the summer gap of seasonal growth of cool season grasses. While some legumes such as clovers may not completely fill that gap (although they help substantially), others like alfalfa and lespedeza may provide summer-long forage production. Adding legumes to fields containing high levels of endophyte-infected fescue will also help reduce the summer slump that results from fescue toxicity.
Before adopting any practice a producer should always calculate the potential benefits and compare them to the costs. Adding legumes into cool season grass pastures is an option that pays you back quicker than almost any other strategy in farming. As the price of nitrogen fertilizer goes higher, the benefits of legumes do so as well.
Wesley Tucker is a University of Missouri Extension agriculture business specialist in Polk County.