Cultivars of Canola Respond Similarly to Applied Nitrogen in N-Deficient Soils of South Western Australia

ABSTRACTSix cultivars of canola (Brassica napus L.) were grown with six levels of applied nitrogen (N) fertilizer (Urea 46% N) at six locations in south Western Australia (SWA) during 2010 and 2011. The aim of the experiment was to determine if the seed yield (SY) increase (response) of the canola and associated herbicide technologies were different to applied N. Open Pollinated (OP) and hybrid cultivars of associated herbicide technologies (Triazine Tolerant, TT; Roundup Ready, RR; Clearfield, CL) were used. Varieties had large SY differences with no N applied. Generally, RR hybrid of 2011 tended to have the highest SY, except for Katanning 2011 where several varieties obtained the same SY. The average amount of N required for 90% of the maximum SY was 113 kg N ha−1 and economic breakeven N rates were less than or equal to 100 kg applied N ha−1. The average rate of return on investment in fertilizer N was a $1.60.In 4 out of 6 experiments RR hybrids had the highest oil concentration with no applied N. Ni...