The influence of spring nitrogen on yield, yield components and glucosinolate content of autumn-sown oilseed rape (<i>Brassica napus</i>)

SUMMARY The response of low glucosinolate, low erucic acid (double low) cultivars of oilseed rape to spring nitrogen application was examined at Cockle Park, Northumberland in three successive seasons (1987–90). Seed yield and protein content increased in response to increasing nitrogen application. In each season over 85% of the maximum recorded yield was obtained with an application of 150 kg N/ha. In the absence of spring nitrogen, seed yield varied considerably over the three seasons. The variation in seed yield and protein content between 1987/88 and 1988/89 can partly be explained by differences in the availability of soil nitrogen in the different seasons. Seed glucosinolate concentration was significantly increased withnitrogen applications between 0 and 150 kg/ha. Increasing nitrogen beyond 150 kg/ha hadlittle or no effect on seed glucosinolate concentration. The results are examined with reference to the varying effects of increasing nitrogen application rates on seed glucosinolate concentrations reported previously.