Wonder Ngezimana and Gert Andries Agenbag
Canola is becoming a major source of vegetable oil with increasing demand in South Africa, yet low yields are presently experienced in production areas of the Western Cape Province. Crop response to fertiliser applications in field trials under rainfed conditions are often poor, because of a large number of growth factors that may limit growth and yield. To determine how canola responds to nitrogen (N) with no (low) and high sulphur (S) rates under ideal conditions in a controlled environment, a 5 x 2 factorial experiment, with N (0, 40, 80, 120 and 160 kg ha-1 ) and S (0 and 40 kg ha-1 ) fertilisation rates, was conducted. Plants were irrigated with a nutrient solution which contained all nutrients, but with very low N and S contents. Nitrogen application significantly increased leaf area, hence dry mass accumulation and ultimately flowering and pod formation, but high N and S application levels during early growth stages may have a negative effect on growth. Significant interaction between N and S were shown, however the positive effects of S were more pronounced in the reproductive phases. In this experiment, conducted under controlled temperature and watering conditions, but short winter daylight lengths, yield components of canola as measured by the number of flowers and pods at 91 DAP tended to reach a peak at application rates of 120 kg N ha-1 and 40 kg S ha-1 .
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