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Extension by Islam

by Wyoming Livestock Roundup

Grass-Legume Mixture Has Multiple Advantages in Forage Production Systems

 By Anowar Islam, UW Extension Forage Agroecologist

The cost of fertilizer nitrogen (N) has increased substantially during last few years. This situation is causing a re-evaluation of synthetic fertilizer N use on farms and ranches, and it is generating a renewed interest in lower cost alternatives to sustain productivity. 

Forage legumes offer the potential to lower fertilizer N costs on agricultural lands and may be a more sustainable option for pasture-based production, not only economically but also in terms of impact on water quality, fossil fuel consumption and climate variability. Other advantages include increased productivity, improved quality, increased hay-curing ability and increased stand persistence. However, sustaining forage productivity using legumes requires establishment of an optimal balance of legume to grass biomass in mixtures.

Researchers in the Department of Plant Sciences at the University of Wyoming are trying to find appropriate options through identifying an optimal grass-legume balance in mixture that sustains high yield stability over time and quantifying legume N contribution to grass growth and its variation across environments.

A study was initiated in fall of 2009 at the James C. Hageman Sustainable Agriculture Research and Extension Center (SAREC) near Lingle under irrigation with one grass (‘MaxQ’ tall fescue) and one legume (‘Ameristand 403T’ alfalfa) as test species. Ten treatments repeated three times included five grass-legume mixtures, which included grass-legume seed ratios 1:0, 0.75:0.25, 0.50:0.50, 0.25:0.75 and 0:1, with no supplemental N and five N application treatments of 45, 90, 135, 180, and 270 pounds N per acre to tall fescue monoculture plots. The seeding rate for both tall fescue and alfalfa was 22 pounds pure live seed per acre. The N was applied in two split applications. Three harvests were made in both 2010 and 2011, and two harvests have been made so far in 2012.

Data from this study are in the process of compilation, however, initial data showed promising results. The highest yield, 9,200 pounds per acre, was obtained from 0.50:0.50 tall fescue-alfalfa mixture treatment followed by 0.25:0.75 tall fescue-alfalfa mixture, which yielded 7,300 pounds per acre, and tall fescue with 180 pounds N, which saw 7,250 pounds per acre, treatments.

Interestingly, no difference was observed between 0.25:0.75 tall fescue-alfalfa mixture and tall fescue 180 pounds N treatments. The 0.50:0.50 tall fescue-alfalfa mixture treatment produced more than a 100-percent increase in yield compared to only tall fescue plots, which showed 4,430 pounds per acre. Forage yield decreased to 6,500 pounds per acre at the highest N application, which was 270 pounds N per acre. There were variations among treatments for forage quality especially for crude protein, which ranged from nine to 20 percent, with higher crude protein in higher proportion of legume mixtures and higher N treatments.

From this ongoing study, it is expected that selection of appropriate grass-legume mixture may sustain high yield stability over time and provide economic benefits to producers through high forage yield and quality and reduced input costs. We will continue to update results in the future.

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



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