Using different nitrogen and compost levels on lettuce grown in coconut fiber

The present investigation was conducted for two seasons (2006 and 2007) into white polyethylene container filled with coconut fiber, to study the effect of three nitrogen levels (50, 100 and 150 ppm) applied by fertigation system and three compost levels (0, 2 and 4% by volume). Lettuce plant (Lactuca sativa L.) with two types' iceberg and romaine lettuce were transplanted in October to study the effect of treatments on vegetative growth, nutrients content (nitrogen, phosphors, potassium, calcium, magnesium and nitrate) as well as total yield. The experimental design was a split- plot with three replications. The obtained results indicated that the increasing nitrogen level up to 150 ppm significantly increased plant height, number of leaves per plant, dry weight and yield. Compost at 4% gave the highest vegetative growth and yield comparing with the other treatments. The highest nitrogen level (150 ppm) combined with compost 4% increased significantly vegetative growth and total yield of lettuce. On the other hand, 50 ppm nitrogen gave the highest nitrogen use efficiency (NUE) and the least value of nitrate content in leaves followed by 100 ppm.   Key words: Lettuce, polyethylene container, nitrogen use efficiency, coconut fiber, nitrate.