This investigation was carried out during two successive winter seasons of 2007 / 2008 and 2008/ 2009 at Moshtohor Experimental Farm , Faculty of Agriculture, Benha University to study the effect of applying different nitrogen sources at the recommended dose of N, i.e., mineral nitrogen (ammonium sulphate) and organic nitrogen (biogas manure) and their combination as well as two potassium fertilizers in the form of potassium sulphate as soil addition and potassium oxide as foliar application, either single or in combination with others or with nitrogen sources on plant growth, yield and its components, as well as chemical constituents of onion plant parts (Allium cepa L.) cv. Giza-20.
Obtained results indicated that, using nitrogen fertilizer in the form of 50% mineral –N +50% organic –N recorded maximum values of plant growth characters, expressed as plant height, number of leaves/plant, fresh and dry weight of leaves and bulbs, plant fresh and dry weight, neck and bulb diameter, bulbing ratio, percentage of total N, P and K in leaves and bulbs, bulb yield and its components i.e., average bulb weight, total, marketable and exportable yield . It increased the nutritive value of bulb expressed as N, P, K and T.S.S. percentage compared to the other tested treatments.
Application of potassium as 24 kg K2O/fed as(potassium sulphate)as soil application plus 2% potassium oxide as foliar application being the best treatment which led to the vigor plant growth, higher minerals content of leaves and bulbs, heaviest bulb yield and the best physical and chemical proprieties of bulbs.
It could be concluded that using 50% mineral-N +50% organic-N in combination with 24 kg K2O/fed as soil application+2% potassium oxide as foliar spray proved to be the most effective treatment to obtain vigor plant growth, highest total, exportable (grade 1and 2)and marketable(grade 1,2and 3) of yield /feddan and the best quality of onion bulbs as well as lowering cost production and it may be a way to reduce the environmental pollution.