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Abstract
The effects of nitrogen on yield, 1000-seed weight, oil percentage, and percentages of major fatty acids of the biennial rape seed variety Rangl. were determined in three field trials sown at Lincoln on 23 March 1966, 15 April 1966, and 19 April 1967. Nitrogen was broadcast as granules of ammonium nitrate + lime at rates of 0, 39, or 78 lb N per acre in autumn or in spring, and at 39 lb in autumn and 39 lb in spring. The effects of disulfoton, a granulated systemic insecticide, at 2 lb active ingredient (a.i.) per acre on these characters were investigated in the trial sown in 1967.
Nitrogen at 39 lb and 78 lb per acre increased seed yields from 310 lb per acre to 700 lb and 1,250 lb per acre respectively in the first trial, and from 1,640 lb per acre to 2,390 lb and 2.710 Ib per acre respectively in the second trial. There were no significant differences between autumn and spring applications of N. There were no significant effects from N in the third trial.
Five weeks after sowing, aphid numbers were considerably lower on disulfoton plots, but at the end of June all aphids had died on both disulfoton and untreated plots. Disulfoton had a significant effect on plant size and increased seed yield from 1,680 lb to 2,540 lb per acre. Differences due to infection with the aphid-transmitted cauliflower mosaic virus and turnip mosaic virus may have been the cause, although no outward virus symptoms were detected.
There were no significant effects of nitrogen or disulfoton on 1000- seed weight oil percentage, and percentages of palmitic, oleic, linoleic, eicosenoic, and erucic acids. The percentage of linolenic acid appeared to be slightly decreased by nitrogen in the first trial.
In 1968–69 disulfoton gave a significant increase in seed yield of Moana rape; there were no significant differences between rates of 1 lb and 2 lb a.i. per acre.