Optimal grazing management to achieve high yields and utilisation of dryland lucerne

Abstract

The pre- and post-grazing dry matter yields from six individual paddocks in a grazed lucerne rotation were compared at Ashley Dene, Lincoln University, over 5 years. The mean annual yield was ~12 000 kg DM/ha and unaffected by the rotation order in which paddocks were first grazed in spring. On an annual basis the post-graze residual was about 1000 kg DM/ha lower from Paddock 1 than Paddock 6. First grazing usually occurred with ewes and lambs in the third week of September when the pre-grazing height was 15-25 cm. Rapid spring growth of lucerne meant Paddock 6 was sometimes over 40 cm tall with a pregrazing mass of 4000 kg DM/ha upon first entry 4-5 weeks later. The grazing interval between the first and second rotation in spring was between 29 and 36 days. There was an average 1800 kg DM/ha more on offer in Paddock 6 than Paddock 1 in the first rotation. On average, the ewes and lambs consumed ~2100 kg DM/ ha at ~75% utilisation from each paddock in the first rotation. Weaned lambs offered similar pre-grazing yields consumed less herbage (~1700 kg DM/ha) at ~60% utilisation. A lower pre-graze target for lambs (2000-2500 kg DM/ha) is therefore recommended, particularly if there is no other class of stock available to consume the residual. This may require a quicker rotation with weaned lambs than the 34 days averaged in this study. For ewes and lambs the target of ~3000 kg DM/ha (~30-35 cm pre-grazing height) used for this study seemed appropriate rather than a fixed number of days or particular phenological stage. Keywords: alfalfa, lucerne, Medicago sativa L., rotational grazing, stock class, utilisation