EFFECTS OF TALL WHEATGRASS WINDBREAKS ON HAY PRODUCTION OF 3 ALFALFA VARIETIES AT A SEMIARID LOCATION IN SASKATCHEWAN

Soil water limits alfalfa (Medicago sativa L.) growth in semi-arid sou thwest Saskatchewan. The dry matter yields of three alfalfa varieties with contrasting growth habits were compared when grown between tall w heatgrass [Thinopyrum ponticum (Podp.) Barkworth & D.H. Dewey] windbre aks spaced on 15-m centres, and when grown without windbreaks. Over a 7-yr period, and including the area occupied by the windbreaks, alfalf a yields were 2110 kg ha(-1) dry matter on average. This was 40% more dry matter than from alfalfa grown outside the windbreaks. There were no consistent yield differences between the three varieties, but Beave r, a branch-rooted variety, produced more dry matter than Angus, a tap -rooted variety with fast regrowth potential, and Rangelander, a creep ing-rooted variety, in the years when differences reached significance , and on average over the 7-yr period. Alfalfa regrowth was sufficient for a second cut in 3 of 7 yr. Cultivating to a depth of 35 cm with a Paraplow subsoiler prior to seeding had no effect on hay yields.