The effect of spring grazing management on yield, animal liveweight gain and root reserves of lucerne (Medicago sativa L.).

Lucerne (Medicago sativa L.) is a common pasture legume grown in New Zealand. Rotational grazing is recommended for ensuring stand production and persistence. However, during lambing set stocking ewes and lambs is the preferred management practice. Two grazing experiments were conducted to quantify the effect of spring grazing management treatments on animal and plant production with emphasis on the amount and composition of perennial (crown and root) dry matter. Rotationally grazed plots had an average yield of 15 t DM/ha. Mean annual liveweight production was reported as 1702 kg LW/ha/yr for all stock which grazed lucerne under a rotational regime for the 2010/11 season. Set stocked and semi set stocked mean annual liveweight production was 1452 and 1355 kg LW/ha/yr, respectively. Plant population was found to be 205/m² under in lucerne semi set stocked in spring. Water soluble carbohydrates in the crown portion of the root were higher under rotational grazing at 145 kg/ha. Values for set stocked and semi set stocked grazing were also different with 110 and 122 kg/ha for each treatment respectively. Set stocked and semi set stocked lucerne had liveweight production comparable to rotational during spring, however the management practices resulted in reduced perennial root reserves, and suggested reduced persistence of the stand in the long term.