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Abstract
Two field experiments were carried out during the two successive winter seasons of 2000- 2001 and 2001 - 2002 at El- Khatara Experimental Farm, Fac. Agric., Zagazig University. This study was about the response of onion crop to nitrogen and potassium rates (60 kg N + 75kg K20, 80 kg N + 100 kg K20 and 100 kg N+ 125 kg K20/fed.) fertigation compared to soil application. It aimed also to study the effect of water quantity (1500, 2500 and 3500 mJ/fed.) combined with the above mentioned N + K20 rates under sandy soil condition. The results, generally, indicate that fertigation method significantly increased plant height, number of leavesl plant, dry weight of root, leaves, bulb/plant, chlorophyUs and carotenoids concentration in leaves tissues, total uptake ofN, P and K as well as yield and its components, i.e., total, marketable, exportable and grades (1 and 2) compared to soil application method. Addition of the highest dose of combined N + K20 (100 kg N + 125 kg K20/fed.) and the two high water quantities (2500 or 3500 m 3 Ifed.) being the best treatments which significantly increased all the above mentioned studied parameters, compared to low levels of both fertilizer (60 kg N + 75 kg K20/fed.) and water quantity (l500m3 water I fed.). Water quantity at 1500 mJ Ifed and N+ K20 at 80 + 100 kg/fed recorded the maximum water use efficiency. The best interaction treatments for onion growth and yield were application of 80 kg N + 100 kg K20 and 100 kg N + 125 kg K201 fed. via fertigation and also, application of 2500 or 3500 m3 water I fed combined with 80 kg N + 100 kg K20 and 100 kg N + 125 kg K20 Ifed.