Grass‐Legume Seed Mass Ratios and Nitrogen Rates Affect Forage Accumulation, Nutritive Value, and Profitability

Abstract

Grass‐legume mixtures are considered viable alternatives to nitrogen (N)‐fertilized grass pastures, but there is a dearth of information on effects of seed mass ratios on productivity and economic returns. We evaluated the effects of grass‐legume seed mass ratios and N fertilizer rates on forage accumulation, nutritive value, and profitability. There were 15 treatments arranged in randomized complete blocks with four replicates. The treatments included four species (meadow bromegrass [Bromus biebersteinii Roem. & Schult] and three legumes—alfalfa [Medicago sativa L.], sainfoin [Onobrychis viciifolia Scop.], and birdsfoot trefoil [Lotus corniculatus L.]), various seed mass ratios (100:0, 50:50, 70:30, 50:25:25, and 50:16.7:16.7:16.7), and three rates of N (0, 56, and 112 kg N ha−1) applied only to meadow bromegrass monocultures. The 2‐yr average annual forage accumulation of meadow bromegrass receiving 112 kg N ha−1 was 6.89 Mg ha−1 yr−1, which was similar to the 30% alfalfa + 70% meadow bromegrass, 30% birdsfoot trefoil + 70% meadow bromegrass, 25% alfalfa + 25% birdsfoot trefoil + 50% meadow bromegrass, and 50:16.7:16.7:16.7 mixture treatments. Mixtures had greater nutritive value than N‐fertilized meadow bromegrass. All treatments except 100% sainfoin and 50% sainfoin + 50% meadow bromegrass treatments were profitable. On the basis of forage accumulation, nutritive value, and profitability, the 30% alfalfa + 70% meadow bromegrass and 30% birdsfoot trefoil + 70% meadow bromegrass seed mass ratios are simple mixtures that may be viable alternatives to 100% alfalfa and N‐fertilized meadow bromegrass monocultures.