Herbage Production: Conventional Mixtures vs. Alternating Strips of Grass and Legume
- N.A. Fairey and
- L.P. Lefkovitch
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: N0 = no N, NGL = 150 kg ha−1 N applied uniformly to grass and legume; and NG = 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 N0 (1.80-0.92 t ha−1) and NGL (3.67−2.56 t ha−1), but was unaffected by strip width with NG (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 N0, NGL, and NG, respectively; it was 658 and 375 g kg−1 for the conventional mixture with N0 and NGL, respectively. Stripculture 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.
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