Lucerne (Medicago sativa L.) sowing rates were evaluated to determine how environmental conditions affect seedling establishment and plant survival. Lucerne (cv. Peace:, was sown during 1988 at rates ranging from 2.8 to 11.2 kg ha(-1) at one irrigated and two dryland sites (a forest and a mid-elevation grassland site) near Kamloops, British Columbia, Canada. Dry matter (DM) yield was measured for 3 years, and plants were counted to estimate seedling establishment and plant survival. Sowing year DM yield increased linearly with sowing rate at the irrigated and forest sites, but at the mid-elevation grassland site it decreased at sowing rates > 5.6 kg ha(-1). In the first full-production year, DM yield levelled off at sowing rates > 8.4 kg ha(-1) at the irrigated site and was not affected by sowing rate at the forest site. At the grassland site, first full-production year DM yield decreased at sowing rates > 2.8 kg ha(-1). In the second full-production year, there was a linear effect of sowing rate on DM yield at the irrigated site, but it did not affect DM yield at the two dryland sites. At all sites, the percentage of seedlings that survived to the end of the second growing season decreased curvilinearly as seedling density increased. Survival was less at the irrigated site than at the dryland sites. Higher sowing rates are required at irrigated sites than at dryland sites to obtain maximum yield or a required plant population density.
