Grass-Legume Mixtures to Mitigate Nitrogen Need and Improve Soil Properties in the Great Plains of Wyoming.

Grass-legume mixtures may improve forage yield, forage quality, stand persistence, and soil properties. The objectives of this study were to increase yield and quality of forage, improve soil properties, reduce production costs, and improve long-term profitability and sustainability of forage production systems. The study was established at two locations (Lingle and Laramie, Wyoming) during 2011-2012. Meadow brome, orchard grass, and alfalfa were the test species. Sixteen different treatment combinations included monoculture grass, monoculture legume, two grass mixtures, one grass and one legume mixtures, and two grasses and one legume mixtures. Monoculture grass and two grass mixtures received either no nitrogen (N) or N fertilizer (150 kg N ha^-1 as urea) whereas grass-legume mixtures received no N fertilizer. The experimental design was RCBD with three replications. Soil analyses at both locations showed the range of 0.74-0.91%, 3.34-5.23 mg kg^-1 day^-1, and 0.07-0.09% for organic C, labile C, and total N, respectively. In 2012, the plots were harvested four times at Lingle and one time at Laramie and growth, yield, and quality data were measured. Significant responses were observed from different treatments. In Lingle, total dry matter (DM) yield from four harvests ranged 7,943-13,504 kg ha^-1 and in Laramie, total DM yield from one harvest ranged 156-3,819 kg ha^-1. The highest total DM yield (13,504 kg ha^-1) was obtained from 50%:50% mixture of alfalfa and meadow brome at Lingle. Crude protein (CP) ranged from 155-269 g kg^-1 for both locations and the highest CP production (3,692 kg ha^-1) was from 50%:50% mixture of alfalfa and orchard grass at Lingle. The DM and protein yields from 50%:50% mixture were higher than the 150 kg N ha^-1 treatment (8,451 vs. 1,622 kg ha^-1) indicating this mixture can mitigate N need and improve forage quality. Data will be discussed in details in the presentation.