This is a refereed journal and all articles are professionally screened and reviewed ORIGINAL A RTICLE Advances in Environmental Biology, 3(3): 337-346, 2009 ISSN 1995-0756 © 2009, American-Eurasian Network for Scientific Information 337 Corresponding Author Ahmed Mohamed Elhasan Rugheim, Faculty of Agriculture, Omdurman Islamic University, Omdurman, Sudan. E-mail: arugheim@gmail.com Effects of Rhizobium and Bacillus Megatherium Var. Phosphaticum Strains and Chemical Fertilizers on Symbiotic Properties and Yield of Faba Bean (Vicia Faba L.) Ahmed Mohamed Elhasan Rugheim and Migdam Elsheikh Abdelgani 1 2 Faculty of Agriculture, Omdurman Islamic University, Omdurman, Sudan. 1 Environment and Natural Resources Research Institute, the National Centre for Research, Khartoum. 2 Sudan. Ahmed Mohamed Elhasan Rugheim and Migdam Elsheikh Abdelgani: Effects of Rhizobium and Bacillus Megatherium Var. Phosphaticum Strains and Chemical Fertilizers on Symbiotic Properties and Yield of Faba Bean ( Vicia Faba L.): Adv. Environ. Biol., 3(3): 337-346, 2009 ABSTRACT A field experiment was conducted for two consecutive seasons to examine the effect of inoculation by different Rhizobium and phosphate solubilizing bacteria strains and their interaction on symbiotic properties and yield of faba bean, and to compare between the effects of chemical fertilizers and biofertilizers. Both Rhizobium and phosphate solubilizing bacteria significantly increased yield and symbiotic properties (nodulation, nodules and shoots dry weight, and plant nitrogen and phosphorus content) of faba bean plants. A synergetic effect was observed when the two types of microorganisms were combined. Comparable increments in yield were obtained resulting from either microbial fertilizers (nitrogen fixing and/or phosphate solubilizing bacteria) or chemical fertilizers (nitrogen and phosphorus fertilizers). Key words: Rhizobium, Bacillus, Vicia faba, nitrogen fixation, phosphorus solubilizing bacteria. Introduction Faba bean ( Vicia faba L.) is one of the most important grain legumes cultivated in the Sudan. It is mainly grown for human consumption and constitutes the main dish in two daily meals. Most of the production in Sudan is concentrated in the Northern and River Nile states [7]. The most limiting nutrients for plant growth and production are nitrogen and phosphorus. In the last few decades the use of nitrogen fertilizer has increased almost ninefold and phosphorus more than fourfold [13]. The increase in use of chemical fertilizers has created environmental problems such as deterioration of soil quality, surface and ground water as well as air pollution, reduced biodiversity and suppressed ecosystem function [13]. The use of biofertilizers is gaining attention to substitute, and supplement these chemical fertilizers. Biofertilizers include mainly the nitrogen fixing, phosphate solubilizing and plant growth–promoting microorganisms. Rhizobium-legume symbioses are the primary source of fixed nitrogen in land based systems, and can provide well over half of the biological source of fixed nitrogen. Inoculation of faba bean with local or introduced cultures of Rhizobium leguminosarum bv. Viceae was found to improve nodulation, plant growth and grain yield in Central Sudan [2]. The use of phosphate solubilizing bacteria as inoculants simultaneously increases P uptake by the plant and crop yield. Strains from the genera Pseudomonas and Bacillus are among the most powerful phosphate solubilizers [10]. The effect of a combined