Seasonal growth of lucerne (Medicago sativa) under rainfed conditions in south east Australia: Variation of experimental and commercial cultivars sourced from Australia and China

Seed distributors market lucerne to farmers based on the supposed winter activity of those cultivars. This study determines the amount of between-cultivar variation, in cultivars available to farmers, in annual dry matter production and seasonality of that dry matter production when grown in dryland grazing areas of south east Australia. Forty-seven cultivars of lucerne, that spanned the range of winter activity ratings, were defoliated every 6 weeks for a period of nearly four years at two contrasting dryland sites. At each site, annual and seasonal dry matter growth was measured over three yearly periods. The variation between cultivars was examined using models with random between-cultivar effects. At both sites and in most years, within the Australian commercial cultivars, the higher (97.5% quantile) annual growth cultivars had about 20–30% greater annual growth than the lower (2.5% quantile) annual growth cultivars. Whilst variation between cultivars in seasonality of growth was statistically detectable, the main feature was the small magnitude of this between cultivar variation. We suggest that dryland farmers in temperate regions (similar to south-east Australia) should make purchasing decisions of lucerne cultivar based on annual production, pest and disease resistance, persistence and grazing tolerance, and mostly ignore differences in seasonality of production.