LUCERNE GRAZING MANAGEMENT .1. EFFECT OF GRAZING DURATION ON HERBAGE ACCUMULATION

Irrigated 'Wairau' lucerne (Medicago sativa L.) was grazed with sheep during summer and autumn, using two grazing durations of 3 and 12 days. Similar spelling periods to the early flower stage of growth occurred between successive grazings. This was carried out over two grazing and regrowth cycles. Weekly measurements of regrowth following grazing showed that for both cycles, regrowth in the early stages was more rapid following a 12-day grazing duration than following a 3-day grazing duration. The superiority developed initially was maintained until the early flower stage. Yields of herbage were 4170 and 2435 kg dry matter (DM)/ha for regrowth periods following grazing for 12 days. Corresponding yields following grazing for 3 days were 4000 and 2350 kg DM/ha. Crown shoot and bud counts following the second grazing showed that the faster initial regrowth was a result of a greater number of new shoots ready to begin extension growth, despite some of the new shoots being damaged by grazing in the latter stages of a 12-day grazing duration. The significance of these findings in the grazing management of lucerne is discussed, and is compared with findings from simulated grazing studies. For simple lucerne management systems a duration of 10-12 days may be otpimal, but this will vary with stage of maturity at the start of grazing.