This book basically based on an applied research whose main objectives were to: 1.To see the effect of different phosphorus levels on growth and nitrogen fixation by mash bean. 2.To determine the optimum level of phosphorus for nitrogen fixation by mash bean. In the course of this research experiment we concluded that N2 fixation capacity and yield components of mash bean were enhanced by the application of phosphorus. Response of mash bean was more pronounced to the highest and medium levels of phosphorus fertilization as compare to low level of phosphorus and control.