Response of Brassica napus to rates and time of nitrogen application

Estudou-se, em 1983, na serra do sudeste do Rio Grande do Sul, o efeito de doses crescentes de N no rendimento de grãos e nos teores de óleo e proteína da colza (Canola), cv. CTC-4. As doses de zero, 50, 100, 150 e 200 kg de N/ha foram distribuídas em blocos ao acaso, com seis repetições. Houve resposta da colza a 100 kg de N/ha. Em 1984, devido a fatores ambientais, mudou-se o esquema experimental para parcelas subdivididas, com quatro repetições. As doses de N aplicadas foram: toda a dose na semeadura e 1/3 na semeadura + 2/3 aos 30 e 60 DAE, compondo as parcelas; e as doses de zero, 60, 120 e 180 kg de N/ha, compondo as subparcelas. Houve resposta a 100 kg de N/ha, aplicadas em 1/3 na semeadura mais 2/3 aos 30 DAE. As maiores doses de N homogeneizaram o florescimento a partir dos 43 dias de idade na cultura semeada em agosto. O teor de óleo nos grãos decresceu linearmente com o aumento das doses de N, e os teores de proteína bruta aumentaram.A field trial was conducted, in 1983, in the southeast region of Rio Grande do Sul, Brazil, to evaluate the effect of rates and time of N application on grain yield, oil and protein content of colza (canola) cv. CTC-4. Five rates of N - zero, 50, 100, 150 and 200 kg - were evaluated in a randomized complete block design with six replications. Colza yield responded to 100 kg of N/ha. In 1984, the doses and time of N applications were changed. Zero, 60, 120 and 180 kg of N/ha dose were applied; treatments being: a complete dose incorporated to the soil at planting and 1/3 at planting plus 2/3 at 30 and 60 days after emergence. Time of application (main-plots) and doses (sub-plots) of N were tested in a randomized complete block design with four replications. In the two seasons grain yield was higher when 1/3 of 100 kg/ha of N was incorporated to the soil at planting and 2/3 top dressed 30 days after emergence in the dry season; in the rainy season, the applications of 1/3 at planting followed by top dressing of 2/3 at 60 days after emergence was more efficient. A general decrease in the oil content, and an increase in the protein content were observed with increasing of the doses of N. The blooming date of colza was influenced by the N doses