Dry matter production of Lucerne (Medicago sativa L.) under rotational grazing at Ashley Dene

Abstract

Lucerne (Medicago sativa L.) is a key legume for dryland farming systems in New Zealand. This experiment compared dry matter production of seven lucerne cultivars across six paddocks in a rotationally grazed system. Differences were observed in the dry matter production across the entire experiment. ‘Kaituna’ and ‘Stamina 5’ produced total annual yields of 13.3 t DM/ha, compared with 11.4 t DM/ha from ‘Runner’. Season had the greatest influence on yield, with the 48% of annual production occurring in spring. Timing of grazing also impacted on dry matter production. In the first rotation Paddock 6 was grazed 28 days after Paddock 1, thus accumulated a further 2.9 t DM/ha. Paddock 6 also had a greater plant available water capacity (PAWC) than Paddock 1, which created a 1.5 t DM/ha yield difference. The greatest influence on cultivar differences was winter dormancy. ‘Stamina 6’ was more winter active (dormancy rating 6), thus was the highest yielding cultivar in the beginning of spring (3.2 t DM/ha). ‘Runner’ was a winter dormant cultivar (dormancy rating 3), thus produced 2.4 t DM/ha in the first rotation. The average nitrogen content of the cultivars was greatest for ‘Stamina 5’ (544 kg N/ha) and lowest for ‘Rhino’ (503 kg N/ha). It was concluded that ‘Kaituna’, ‘Stamina 5’ or ‘Stamina 6’ could be sown as their winter activity ensured they had greater production in early spring and autumn. These three cultivars had an average nitrogen content of 3.3% and an ME content of 10.4 MJ ME/kg DM. The timing of grazing of the first stand should not be delayed as the impact on the quality of the last stand in the rotation is a serious consequence of this.