Evaluation of nitrogen nutrition of canola (Brassica napus L.) in Gorgan area, Iran

In order to study the effect of agricultural management on nitrogen nutrition index of canola، a field experimental was conducted in 2010. Experiment was carried out as a nested completely randomized design with three replications. In this field experiment، 15 canola fields were comparatively studied in three levels of management (optimum، middle، weak) in Gorgan area، Iran. Sampling was performed at four stages and characteristics including plant density and height، leaf area index، dry weight، total nitrogen percent، biological yield and harvest index were measured. Also، nitrogen nutrition index was determined at stem formation، flowering and carpetbag stages. The results showed that all the studied management levels and farms within each level were significantly different from nitrogen nutrition index point of view. Positive significant correlation between nitrogen nutrition index with seed and biological yeild at yellow bud stage revealed the importance of nitrogen sources access at flowering and seedbag filling stages. Although nitrogen nutrition index was higher in optimum level of management than in the middle and weak ones، but during growing season and in all management levels، the index was less than 1 that indicates nitrogen deficiency. Thus، it could be concluded that nitrogen is a limitation factor in canola production in Gorgan area، Iran.