Effect of high lucerne (Medicago sativa L.) sowing rates on establishment year yield, stand persistence and forage quality

The effect of very high sowing rates on establishment year dry matter (DM) yield and stand persistence of irrigated lucerne (Medicago sativa L.) was studied. Two cultivars ('Peace' and 'Apollo II') were sown in 1986 at two row spacings and six sowing rates from 5.6 to 50.4 kg ha(-1). Established seedling density (S-d) increased linearly with sowing rate(R):S-d = 24.1 R. Establishment year DM yield increased at sowing rates from 5.6 to 16.8 kg ha(-1), levelled off as sowing rate increased to 33.6 ka ha(-1), and then decreased as sowing rate increased further. Thus, there was a broad optimum sowing rate that gave a maximum sowing year DM yield. Percent plant survival to the third year (1988) decreased with increasing sowing rate so that plant densities became similar for sowing rates greater than 16.8 kg ha(-1). Within the range 5.6 to 16.8 kg ha(-1), increasing sowing rate increased stand persistence measured as 1988 plant density; however, a corresponding increase in DM yield was not obtained. For all full-production years, DM yield was independent of sowing rate. Sowing rate did not affect three chemical measures of forage quality.