Yield and Yield Components of Rapeseed as Influenced by Water Stress at Different Growth Stages and Nitrogen Levels

Irrigated rapeseed (Brassica napus L.) cultivation is currently expanding in rotation with winter cereals in Iran where its reproductive growth is often exposed to water deficit in many parts, particularly in the south. A two growing seasons (2006-2008) field experiment was conducted at the Experimental Research Center, Shiraz University to study the effects of water stress at different growth stages [Normal irrigation at all growth stages (control), water stress at flowering, at pod development and at seed filling stages] and nitrogen (N) levels (0, 75, 150 and 225 kg ha ) on yield and yield components of rapeseed (Telayeh cultivar). The design was split -1 plots arranged in randomized complete block with four replications. Full irrigation and the highest N level had the highest plant height, number of branches per plant, pods per plant, seed and oil yields. However, increased N levels decreased seed oil content and had no significant effect on 1000-seed weight. Flowering was the most sensitive stage for water stress damage resulting a drastic reduction in seed and oil yields by 29.5% and 31.7%, respectively. Pods per plants was the most sensitive yield components to water stress during reproductive growth in both year and it had the highest significant positive correlation with seed and biological yields. The seed and oil yields of the 1 season were more than the 2 season due to favorable weather conditions for st nd growth. Overall, supplying sufficient water to rapeseed crop, particularly at flowering and pod formation, in comparison with 225 kg ha of N fertilizer are important to produce higher yields. -1