Management of lucerne in the cool season

The performance of dormant and winter-active lucerne (Medicago sativa L.) cultivars was compared under sheep grazing in 2 experiments during the cool season. The objectives were to define the cool season management required for winter active cultivars in sheep farming systems. The 'winter-active cultivars Matador and Rere yielded 1760 and 1220 kg DM/ha compared with 890 and 760 kg from Wairau and Saranac respectively in mid-winter, while the reverse occurred in spring when dormant cultivars yielded 50% more than the winter active. This was related to differing levels of non-structural carbohydrates in roots, which had declined to insignificant levels in Rere and Matador by early spring. June grazing increased spring yields of Wairau by 35% due to control of overwintering aphids, but reduced yield of Rere by 25% due to effects on root reserves. Early September grazing greatly - reduced subsequent lucerne yields at late October and early December grazings, and increased the content of weeds. Our findings show that if farmers graze winter-active lucerne with sheep in winter the advantage in production disappears in spring. Cool-season management which combines the use of dormant and winter-active lucernes is discussed. Keywords winter-active lucerne, dormant lucerne, cool-season grazing, root reserves, lucerne grazing management