Yield and composition of red clover treated with growth regulators in early spring

Abstract

AbstractThe effect of growth regulators on the yield and quality of red clover (Trifolium pratense L.) was assessed in two growing seasons. An early‐flowering cultivar (Florex) and a late‐flowering one (Altaswede) were treated with the growth regulator, daminozide butanedioic acid [mono (2,2‐dimethylhydnizide)] or mefluidide [N‐(2,4‐dimethyl‐5{[(trifluoromethyl)sulphonyl]amino}phenyl) acetamide], either in early (mid‐May) or late (late May) season and at low rate [daminozide, 4kg active ingredient (a.i.) ha−1; or mefluidide, 0·13 kg a.i. ha−1] or twice the low rate (high rate), and compared with no treatment. Red clover yielded two‐ to three‐fold more dry mater (DM) in the first than in the second harvest, and growth regulator treatments did not redistribute yields more evenly between the two harvests. Growth regulator effects on the yield and composition of red clover were mainly confined to the first cut herbage. Daminozide increased first‐cut and annual yields of DM and in vitro digestible DM (TVD); the latter was increased particularly for Altaswede, as compared with the untreated red clover. Mefluidide decreased first‐cut yields of DM and IVD for Florex only, but the annual yields for both cultivars were unchanged by this treatment. Changing the rate or time of growth regulator application did not affect DM or IVD yield in red clover. The treated red clover contained less water‐soluble carbohydrate in the first cut than did the untreated crop. The high rate of daminozide, when applied early, decreased neutral detergent fibre and increased IVD contents in the first‐cut red clover compared with the other combinations of rate and time. Altaswede produced as much DM annually and had a higher IVD content than Florex when these cultivars were cut on common dates, twice during the short growing season in Atlantic Canada.