The effect of time of planting and nitrogen fertilizer on yield attributes of Brassica oilseed crops in the Ord River Valley

Abstract

At Kimberley Research Station in the 1962 dry season, two varieties of Brassica ca.mpe.rtris and one of B. juncea were sown under irrigation at four dates from May 1 to July 2 with six nitrogen fertilizer treatments. Seed yield was reduced with later date of sowing. There was a small linear response to nitrogen fertilizer up to 80 lb an acre nitrogen. Applying half the nitrogen at sowing and half at budding showed no advantage over applying all the nitrogen at sowing. Oil content was also reduced with later date of sowing. Nitrogen fertilizer at the highest level reduced oil content slightly. Although seed and oil yield were highest at the first sowing, dry matter and nitrogen yield of tops were highest at the second sowing. The fall in seed and oil yield with later date of sowing appeared to be associated more with rising temperature during the seed maturation period than with general vegetative performance.