Two field experiments were carried out at the Experimental Station of National Research Centre at Shalakan during the 1998 and 1999 growth seasons to study the response of cowpea plant to different levels of chemical and bio-nitrogen fertilizer . Every experiment included 9 treatments , which were the simple combination between 3 chemical nitrogen fertilizer , i.e. 0 , 50 and 100 kg/fed. and 3 levels bio-nitrogen fertilizer , i.e. 0 , 25 and 50 g/kg seeds . The important results could be summarized as follows : chemical nitrogen fertilization at rate of 100 kg as ammonium sulphate gave the best growth characters of plant . The suitable economic level of biogen is (a bio-fertilizer contain a large number of fixation bacttaria) for cowpea plant is 50 g/kg seeds , where the best growth characters were gained . The heaviest total dry weight of whole plant and its  different parts were obtained by adding nitrogen at rate of 100 kg/fed. in the form of ammonium sulphate with treating cowpea seeds by biogen at level 50 g/kg . seeds . The heaviest yield of dry seeds resulted from cowpea plants which received nitrogen at rate of 100 kg/fed. as ammonium sulphate . The heaviest total dry seeds yield as kg/fed. with best quality were resulted with adding 100 kg/fed. of chemical nitrogen fertilizer and with treating cowpea seeds before sowing by biogen at 50 g/kg of seeds .