Spring growth of lucerne (Medicago sativa L.) after different winter grazing regimes

Abstract

This experiment determined if the removal of basal buds by grazing in autumn/winter affected the timing and amount of lucerne spring growth and development. The experiment was established at Iversen Field Lincoln University, New Zealand, and ran from the 1st of June 2024 to 1st of October 2024 (122 d). Grazing occurred on four dates (1st of June, 3rd of July, 17th of July, or the 1st of August) by mob stocking mixed age Coopworth ewes to simulate a “hard clean-up” winter graze. The start of rapid stem extension in spring occurred at a photoperiod of 10.8 (± 0.2) hours for all treatments. However, shoot biomass differed at each harvest until the 3rd of September. Taproot yield at the final harvest on the 1^st of October was highest in crops grazed on the 1^st of June (3300±124 kg DM/ha) and lowest (1100±124) kg DM/ha) from those gazed the latest on 1st of August. Spring shoot biomass production was unaffected by winter grazing date. However, the ~1000 kg DM/ha lower root yield for lucerne grazed on 1st August, meant the crop would require a longer period of autumn recovery to recharge reserves to maintain stand persistence