Effect of time of application and amount of nitrogen fertilizer on seed yield and concentration of oil in canola (Brassica napus)

ABSTRACTThe seed (grain) yield increases (responses) and concentration of oil in seed responses of canola (Brassica napus L.) to applications of fertilizer nitrogen (N), as urea (46% N), was measured in eight field experiments in south-western Australia (SWA). Nitrogen was applied at five different times of application, either at sowing or at three to four weekly intervals until 12–16 weeks (0, 3, 6, 9, 12 or 0, 4, 8, 12, 16) after seedling emergence. Canola, sown in late May to early June, was grown on a range of soil types in different locations of SWA. The greater the amount of N applied and the closer N was applied to the sowing of the canola seed usually gave the largest seed yield increase at both higher rainfall sites (> 500 mm) and lower rainfall sites (<350 mm). Maximum seed yield of canola were reached within nine weeks after seedling emergence. The exception was for a sandy soil (Fluventic Lithic Xerochrept; Brown Tenosol) at Narrogin where applications of N at six, nine, or 12 weeks after emer...