SEEDBED PREPARATION FOR RAPESEED GROWN ON FALLOW AND STUBBLE

Abstract

Seedbed preparation (SP) systems for Brassica napus and B. campestris cultivars grown on both tilled fallow and on barley stubble were evaluated for 3 yr on Melfort silty clay soil to determine whether the number of tillage operations could be reduced without adversely affecting yield. On fallow, treatments including spring tillage increased the risk of drying out of the seedbed, thereby, delaying crop development and reducing yield. In 1985, this practice delayed maturity by 2.8 d and reduced yield by 225 kg ha−1. In those instances where there were significant differences, SP treatments without spring tillage gave highest yields. Leaving cereal stubble standing over winter to trap snow and incorporating trifluralin in the spring delayed rapeseed maturity by 1.2 d on average. Yield of Tobin rapeseed was unaffected by SP treatment, but the yield of OAC Triton and Westar was highest when tillage was reduced, trifluralin incorporated in the fall and a herbicide used for preseeding weed control in the spring. Direct drilling of OAC Triton gave similar yields to reduced tillage, but this practice resulted in lowest yields of Westar.Key words: Rapeseed, tillage, seedbed, Brassica spp.