A field experiment was conducted in two successive seasons 2001/2002 and 2002/2003 in a sandy calcareous soil at west Samalout, EL-Minia Governorate, to study the effect of applying organic and inorganic nitrogen fertilizers as chicken manure (18.5% N and 30% water content ), ammonium sulfate ( 20.6% N) and their combination on growth parameters         (plant height , bulb diameter , total fresh and dry weight of onion bulb after 100 days of transplanting ), bulb total yield of onion (Allium cepa L) and its N, P and K content . The two single sources of nitrogen fertilizer and their combination were application at five levels that are equal of nitrogen value . 1- Chicken manure was applied at levels of 0.0 , 5.0 , 10.0, 15.0 and 20.0m3 / fed ., that equal of 0.0 , 2.0 , 4.0, 6.0 and 8.0 ton / fed., respectively . 2- Ammonium sulfate was applied at levels of 0.0, 37.0 , 74.0 , 111.0 and 148.0 kg N / fed .  3- Their combination at  levels of nitrogen value :- 1  ton of chicken manure +18.5 kg N of ammonium sulfate / fed.  2 ton of chicken manure+ 37.0 kg N of ammonium  sulfate / fed  3 ton of chicken manure+55.5 kg N of ammonium sulfate/fed.  4  ton of chicken manure+ 74 kg N of ammonium sulfate/ fed. The results indicated that the application of organic , inorganic nitrogen fertilizer and their combination. at different levels significantly increased some growth parameters (plant height, and  fresh and dry bulb weight) after 100 days of transplanting. The total yield and average weight of 10 bulbs also significantly increased with applying different levels of chicken manure and N fertilizer compared with control treatment.  The application of chicken manure, ammonium sulfate and  their combination at different levels significantly increased N, P and K concentration and uptake by onion plants at harvest. Moreover, the increases in the nutrient concentration and uptake by onion due to the application of these sources of nitrogen fertilizers followed the trend of ammonium sulfate + chicken manure > ammonium sulfate alone > chicken manure alone) . Generally the results showed that the addition of 6 to 8 ton of chicken manure with 60 to 70 kg N / fed. as ammonium sulfate recommend to increase the yield of onion and the uptake of nitrogen, phosphorus and potassium by onion