Effect of sowing date and seeding rate on yield and yield components of irrigated canola (Brassica napus L.) grown on a red-brown earth in south-eastern Australia

摘要

Response of canola (Brassica napus) to factorial combinations of five sowing dates and seeding nrates was investigated from 1987 to 1989. The experiments were conducted on red-brown nearths in the Goulburn-Murray Irrigation Region of south-eastern Australia. Crops were sown nat monthly intervals beginning in April each year. In 1987, seeding rates were 4.6, 7.0 and n14 kg ha-', but in 1988 and 1989 the lowest rate was eliminated. The cultivar Marnoo was nused each year and Eureka was included in 1989. nThere was no difference between yields of seed and oil for crops sown in April and May, nbut yields of seed and oil declined when sowing date was delayed beyond May. Oil contents nwere greater than 45% for the April, May and June sowings in 1988 and 1989. In contrast, nseeding rates had no effect on yields of seed and oil. Marnoo produced a maximum seed yield nof 398 g m-2 from the May sowing in 1987, and a minimum seed yield of 172 g m-2 from nthe September sowing in 1988. In 1989, Eureka out-yielded Marnoo in all but the August nsowing. Eureka produced a maximum seed yield of 483 g m-2 from the April sowing and its nlowest seed yield of 315 g mP2 from the August sowing. The number of pods per m2 was nthe major factor responsible for the significant changes in yield in all experiments. Seed yield nwas also strongly correlated (P < 0.01) with biomass, and to a lesser degree, with individual nseed weight in all comparisons with the exception of Marnoo in 1989. nrotations, and (b) the use of mixtures to select medics suitable for such rotations.