Effects of nitrogen fertilizer, cutting frequency, and companion legume on herbage production and quality of four grasses

Carlton smooth bromegrass (Bromus inermis Leyss.), Regar meadow bromegrass (B. biebersteinii Roem et Schult.), Climax timothy (Phleum pratense L.), and Oregon commercial meadow foxtail (Alopercurus pratensis L.) were each grown alone or in binary mixture with Peace alfalfa (Medicago sativa L.), Dawn alsike clover (Trifolium hybridum L.), or Cree birdsfoot trefoil (Lotus corniculatus L.) for three production years under three management systems: two cuts with no nitrogen (N) fertilizer; two cuts with 150 kg ha−1 N fertilizer; and four cuts with 150 kg ha−1 N fertilizer. With two cuts per year and no N fertilizer, herbage productivity of each grass was greater when the grass was grown in association with alfalfa than when grown alone, with alsike clover, or with trefoil. With N fertilization, herbage productivity was reduced by cutting more than twice per year, the magnitude of the reduction being smooth bromegrass > meadow bromegrass > timothy > meadow foxtail; yields of smooth bromegrass were almost halved whereas those of meadow foxtail were virtually unaffected, and this effect was consistent for each companion legume treatment. Under conditions of non-limiting soil-N, herbage productivity and N concentration were controlled more by the adaptation of each grass, and its response to frequency of cutting, than by species composition of the seeding mixture. Without supplemental N fertilizer, alfalfa was the most suitable companion legume to enhance the agronomic performance of each of the four grasses. Key words: Forage, nitrogen, cutting frequency, simulated grazing, grass-legume mixtures