EFFECT OF GRAZING INTENSITY AND NUMBER OF GRAZINGS ON HERBAGE PRODUCTION AND SEED YIELDS OF TRIFOLIUM-SUBTERRANEUM, MEDICAGO-MUREX, AND ORNITHOPUS-COMPRESSUS

The impact of grazing intensity and number of grazings was assessed on the growth and seed production of 5 annual pasture legumes [Trifolium subterraneum var. subterraneum cv. Karridale, var. brachycalycinum cv . Clare, var. yanninicum cv. Trikkala; Medicago murex (murex medic) cv . Zodiac; Ornithopus compressus L. (yellow serradella) cv. Avila]. The re were 7 grazing treatments: an ungrazed control; and 2 grazing inten sities (light and heavy), each for 3 periods of grazing (winter, winte r-early spring, winter-late spring). Tethered sheep in small experimen tal plots were used to provide controlled herbage removal across all c ultivars through winter and winter-spring grazing. This grazing system resulted in significantly different levels of herbage being present i n the light and heavy grazing treatments following each grazing period . Grazing had variable effects on seed production: less-than-or-equal- to 35% increase for Trikkala, and no significant effect for Karridale. Both cultivars continued growth and seed production late in the seaso n after grazing pressure was removed on 8 November. Seed yield of Clar e was reduced by 46-49% by heavy grazing treatments. Seed yield of mur ex medic was not significantly affected by grazing, while that of serr adella was reduced by 30-55% by grazing late in the season. The seed y ield responses show that cultivar and species responses to grazing may be highly variable. Under favourable spring conditions, Trikkala, Kar ridale, and murex medic can be grazed heavily until late in the season without adversely affecting seed yield, whilst Clare and Avila cannot .