YIELD RESPONSE OF RAPESEED TO ROW SPACING AND RATES OF SEEDING AND N-FERTILIZATION IN INTERIOR ALASKA
The effects of row spacings, seeding rates, and N-fertilization rates on yield of Candle, a cultivar of Brassica campestris L., were studied for 2 yr in interior Alaska. Rows were spaced at 18 and 36 cm. Seeding rates were 3, 7 and 13 kg ha−1. Fertilizer N was broadcast at 0, 55, 90, 125, 160 and 195 kg ha−1. Seed yield was not significantly affected by row spacing in either year of the study. Seeding rate did not significantly affect yield in 1978. In 1979, however, an interaction was detected between seeding rate and N-fertilization rate. During this year of abnormally high precipitation, when no N was applied, stands seeded at 3 kg ha−1 produced higher yields than those seeded at higher rates. With an initial N application of 55 kg ha−1, yields decreased from stands seeded at 3 kg ha−1, while yields from those seeded at 7 and 13 kg ha−1 increased. Nitrogen fertilization had a significant effect on yield in both 1978 and 1979. Regression equations from both years (with the exception of that for the 3 kg ha−1 seeding rate in 1979) predicted maximum yields from N applications between 89 and 105 kg ha−1.Key words: Rapeseed, row spacing, seeding rate, nitrogen fertilization, yield