الفهرس 
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Abstract
A pot experiment was conducted at the nursery of Experimental Station Farm, Faculty of Agriculture, Mansoura University during the winter season of 2013/2014 to investigate the effect of soil types, organic fertilizers and nitrogen fertilizer levels as well as their interactions on growth and nutrients concentration and uptake by lettuce (Lactuca sativa L.). The effect of soil types (clay and sandy soils) on growth parameters (plant height, fresh weight of plant and dry weight of plant) and chemical analyses (nitrogen, phosphorus and potassium percentages and uptake by lettuce after 70 days from transplanting and available nitrogen, phosphorus and potassium in the soil after harvesting lettuce plants) was significant in the growing season. Concerning to the effect of organic fertilization treatments i.e. farmyard manure (FYM) at the rate of 20 m3/fed and compost at the rate of 15 m3/fed, the obtained results without a doubt show that organic fertilization treatments show significant effect on growth characters (plant height, fresh weight of plant and dry weight of plant) and chemical analyses (nitrogen, phosphorus and potassium percentages and uptake by lettuce after 70 days from transplanting and available nitrogen, phosphorus and potassium in the soil after harvesting lettuce plants) in the growing season. Nitrogen fertilizer levels i.e. control treatment (without nitrogen fertilization), 50 % of the recommended dose (30 kg N/fed) and 100 % of the recommended dose (30 kg N/fed) had a significant effect on growth characters (plant height, fresh weight of plant and dry weight of plant) and chemical analyses (nitrogen, phosphorus and potassium percentages and uptake by lettuce plant after 70 days from transplanting and available nitrogen, phosphorus and potassium in the soil after harvesting lettuce plants) in the growing season. The obtained results indicate that there was a significant effect due to the interaction between soil types × organic fertilizer on fresh and dry weight of lettuce plants, nitrogen percentage and uptake by lettuce plant, phosphorus percentage and uptake by lettuce plant, potassium percentage in lettuce plant at harvest, available nitrogen, phosphorus and potassium in the soil after harvest in the growing season. The highest values of these characters were resulted from planting lettuce seedlings in clay soil along with organic fertilizing by compost at the rate of 15 m3/fed.