Effects of sowing time, N and P fertilizers on seed yield, oil and protein production in canola

It is just a few years that canola (Brassica napus L.) is grown in Kerman Province, Iran, and little information is available on its response to nitrogen (N) and phosphorous (P) fertilizers. Therefore, a 2-yr field study as a split plot design was conducted at Shahid Zendehrooh Education Center in Kerman, investigating the influence of two sowing dates, early to late Oct. (main plots) and N and P fertilizers (sub-plots) in 3 replications. Canola was sown after barley and alfalfa in 1st and 2nd year of sowing respectively. In early Oct sowing of 1st yr, N and P fertilizers were applied at 300 and 50 kg ha-1 rates for a seed yield of 3.4 t ha-1. Results indicated that in the 2nd year, alfalfa had enriched the soil with N; therefore, for a seed yield of 3.9 t ha-1 in early Oct. sowing, 200 kg N ha-1 was applied while 300 kg N ha-1 reduced the seed yield. Delaying sowing reduced total N concentration in young leaves while decreased seed, oil and protein production. It could be concluded that sowing date, fertilizers application according to soil test results and planting canola after a legume were factors affecting optimum canola yield.