Management of lucerne in the cool season

Abstract

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.