Effect of seeding rate and nitrogen fertilizer on production of autumn sown rape (Brassica napus) on the Central Tablelands of New South Wales

Abstract

Two factorial field experiments, comparing the effects of a range of seeding rates and levels of nitrogen fertilizer on the winter and early spring yield of rape (Brassica napus CV. Dwarf Essex) sown in early autumn, were conducted in two successive years near Orange (33.2¦S, 149.1¦E), New South Wales. Average annual rainfall is 34 inches and winter mean temperatures range from 42-45¦F. Seeding rates of from 9 to 15 lb an acre and nitrogen fertilizer at 80 lb N an acre at seeding gave near optimum winter and early spring yields. This combination gave a three-fold increase in yield over sowings at 3 lb an acre without nitrogen fertilizer. The responses to seeding rate and nitrogen were independent in winter, but these factors interacted to affect yield in early spring. The dry matter content of rape varied between 11.5 and 19.3 per cent and was generally unaffected by seeding rate, but tended to decrease slightly with increased nitrogen level. Nitrogen percentage, which fluctuated between 2.18 and 3.61, was little affected by increased seeding rate and generally showed a small increase with increasing levels of applied nitrogen.