Herbage Production: Conventional Mixtures vs. Alternating Strips of Grass and Legume

Soil N influences the agronomic characteristics of grass‐legume herbage. A conventional grass‐legume stand was compared for productivity, quality, and botanical composition, at two locations for three production years, to three stands comprised of alternating, broadcast‐seeded strips (40‐, 60‐, or 80‐cm width) of pure grass and pure legume. Stands were of smooth bromegrass ( Bromus inermis Leyss.) and alfalfa ( Medicago sativa L.), and were grown under three N fertilizer treatments: N 0 = no N; N GL = 150 kg ha −1 N applied uniformly to grass and legume; and N G = 150 kg ha −1 N but with the distribution of N restricted to plot areas seeded to grass. Grass dry matter (DM) yield declined as strip width increased with N 0 (1.80‐0.92 t ha −1 ) and N GL (3.67−2.56 t ha −1 ), but was unaffected by strip width with N G (3.60 t ha −1 ). Herbage DM digestibility was 698, 699, and 708 g kg −1 for the 40‐, 60‐, and 80‐cm strip‐culture stands, respectively, and 690 g kg − 1 for the conventional mixture. Legume concentration in harvested herbage (DM basis) ranged from 726 to 798, 489 to 524, and 411 to 426 g kg −1 for the strip‐culture stands with N 0 , N GL , and N G , respectively; it was 658 and 375 g kg −1 for the conventional mixture with N 0 and N GL , respectively. Strip‐culture stands have potential for manipulating grass/legume ratios of herbage, and may provide a way to supply optimal N fertilizer to grass plants in grass‐legume associations, without relinquishing the N‐fixing contribution of the legume.