INFLUENCE OF POSTHARVEST RESIDUE MANAGEMENT AND CULTIVAR ON TILLER DYNAMICS AND SEED YIELD IN TIMOTHY

Timothy (Phleum pratense L.) is a bunch-type cool season perennial gra ss species grown in Manitoba primarily for seed production. The object ives of this study were to determine the effect of post-harvest residu e management (straw removal-SR, straw and stubble removal-SSR and fall burning-Burn) on tiller production, yield components and seed yield o f five timothy cultivars (Basho, Climax, Goliath, Hokuo and Salvo), an d to better understand the association between yield components and fi nal seed yield in timothy crops grown in the dry subhumid region of th e Canadian prairies. Two experiments were conducted over four producti on seasons at Arborg, MB and one production season at St, Claude, MB. Tiller number per m(2) in spring (TS) and at harvest (THV) were measur ed in 1990 at St. Claude and in 1990 and 1991 at Arborg. Residue manag ement (RM) treatment ranking for TS was Burn < SR < SSR, but tiller se nescence and compensatory mechanisms resulted in equivalent THV values across all RM treatments. The number of seed-bearing tillers m(-2) at harvest was also unaffected by RM. Seed yield was unaffected by RM in all instances, except at Arborg in 1989 where a significant RM x cult ivar interaction was observed. The basis of the interaction was the gr eater sensitivity of Hokuo to the Burn treatment. Cultivar differences for seed yield were relatively consistent over years and between the two experiments, with Climax always ranking in the high yielding group and Salve with the low yielding group. Based on analysis of yield com ponents, it appeared that RM most affected early season growth (i.e. T S), while cultivar most affected later season growth (fertile tillers per unit area, seed yield per fertile tiller (SYFT)). Seed yield diffe rences were most closely associated with SYFT (r(2) = 0.97*) across c ultivar treatments.