Cool-Season Legumes and Grass Mixtures Overseeded In Tifton 85 and Harvested for Biomass and Forage.

Cool-Season Legume and Grass Mixtures Overseeded in Tifton 85 and Harvested at Biomass and Forage.

Dairy and beef farmers commonly utilize Tifton 85 (Cynodon hybrid) for hay or grazing during the summer months in central Texas.  When Tifton 85 goes dormant to survive the winter, farmers will often overseed the sod with cool-season forages to supplement hay cost and provide high quality grazing. This type of double cropping system could also be conducive to the production of bioenergy feedstocks. However, due to a consistent rise in fertilizer cost, more economical and sustainable means of supplying nitrogen (N) to such systems must be developed. Legumes could possibly provide N to increase forage quality or increase biomass yields with lower inputs. Arrowleaf (Trifolium vesiculosum), hairy vetch (Vicia villosa Roth) and crimson clover (Trifolium incarnatum) were three legumes evaluated.  Grasses used were rye (Secale cereale), oats (Avena sativa), wheat (Triticum aestivum), triticale (X Tritiosecale rimpaui), barley (Hordeum vulgare), and ryegrass (Lolium multiflorum). Pure grass plots were fertilized with 67 kg N ha^-1 in the fall and once in the spring while grasses planted with legumes were fertilized with only one application of 67 kg N ha^-1 in the fall.  Half of the plots were harvested once at peak biomass and half were harvested at a compromise of yield and nutritional quality.  Rye had the greatest carbon (C) yields amongst the grass species when harvest was delayed for biomass production. Grass plots receiving maximum fertilizer produced the highest C yields but hairy vetch, crimson clover, and arrowleaf clover all increased C yields when interseeded without a spring application of N.  N yields were similar among the treatments when harvested for biomass production but when harvested for forage quality hairy vetch plots yielded almost three times as much as the fertilizer treatment. When harvested for forage all three legumes produced significantly more N when planted in pure plots.  Hairy vetch produced over 900 kg N ha^-1 when planted alone and harvested for forage.