Extension Education: Grass-Legume Mixture May Benefit Producers

In one of my articles last year, I discussed that there are many advantages of grass-legume mixtures over the monoculture practices under different growing conditions. Grass-legume mixtures can reduce nitrogen fertilizer requirements because legumes fix atmospheric nitrogen naturally; increase protein and digestibility of the forages; extend grazing periods; are more competitive with weeds; better protect against plant heaving, cold injury and soil erosion because of better coverage; are better cured as hay; tolerate to wide range of soil conditions; reduce bloat potential when mixtures contain 40 percent or more grass; reduce nitrate poisoning and grass tetany potential when mixtures contain 40 percent or more legumes; and reduce lodging potential for legumes. 

These benefits are achievable. However, they depends on weather conditions, soil conditions, locations, elevations, compatibility of the mixture species, adaptability of the forage species and, finally, management practices.

Recent studies by the researchers at the Department of Plant Sciences of University of Wyoming show that grass-legume mixtures could be beneficial for producers in many Wyoming’s environments. 

Several long-term studies have been initiated at the James C. Hageman Sustainable Agriculture Research and Extension Center near Lingle, which sits at about 4,200 feet in elevation, and at the Laramie Research and Extension Center in Laramie, at about 7,200 feet in elevation. In one study, tall fescue and alfalfa mixtures were used. In other studies, meadow brome, orchard grass and alfalfa were used. 

Based on few years’ results, it appears that a 50:50 ratio of grass-legume mixture could increase yield, improve quality and reduce production costs by eliminating use of nitrogen fertilizer in forage production systems in these environments. Alfalfa seems to be a good compatible species with all grasses, including tall fescue, meadow brome and orchard grass, used in the studies. The 50:50 grass-alfalfa mixtures produced more than a 100percent increase in yield compared to only grass plots.

There were variations among mixtures for forage quality especially for crude protein, which ranged from nine to 20 percent, with a tendency of higher crude protein in higher proportion of legume mixtures and higher nitrogen applications. Please note that different rates of nitrogen, including zero, 45, 90, 135, 180 and 270 pounds of nitrogen per acre, were used only in monoculture grasses for comparing production with grass-legume mixtures. Interestingly, 50:50 grass-legume mixtures produced more forage than the highest nitrogen rate of 270 pounds nitrogen per acre. 

It is expected that selection of appropriate and adaptive grass-legume mixture may sustain high‐yield stability over time and provide economic benefits to producers. I will keep updating the results in my future articles.

Anowar Islam is an assistant professor and the University of Wyoming Extension Forage Agroecologist in the Department of Plant Sciences in the College of Agriculture and Natural Resources. He can be reached at 307-766-4151 or mislam@uwyo.edu.