Sod-seeding alfalfa in spring into established crested wheatgrass in southwest Saskatchewan

Abstract

Five experiments were started over a 3-yr period to examine the width of a strip of established crested wheatgrass (Agropyron desertorum (Fisch.) Schult.) that should be killed for reliable establishment of alfalfa (Medicago sativa L.) by sod-seeding in semiarid southwestern Saskatchewan. The value of pruning the grass roots along the edges of the killed area for alfalfa establishment was also examined. When alfalfa seeds were sown in a single row in strips of dead crested wheatgrass, alfalfa establishment improved as the width of the dead strip increased up to 75 cm, the maximum used, because of less competition for moisture and light. Pruning grass roots did not improve alfalfa establishment. Killing the crested wheatgrass in a strip wider than 50 cm favoured weed growth. Annual and biennial weeds were present only in the establishment year, but perennials persisted for the duration of the experiments. Yields of Rangelander, a creeping-rooted alfalfa of mixed ssp. sativa (L.) Lesins & Lesins and ssp. falcata (L.) Arcangeli parentage, and SCMf3713, a tap-rooted ssp. falcata were similar in the seedling and the following year. Etiolated growth of established plants revealed that SCMf3713 had a more persistent recovery characteristic which probably confers survival ability in severe environments. Killing the resident crested wheatgrass benefitted alfalfa establishment, as measured by seedling numbers, growth, seedling and first harvest year yields, and root reserves. Key words: Crested wheatgrass, sod-seeding, alfalfa, Agropyron desertorum, Medicago sativa