The Effect of Phosphorus on Nodulation, Growth and Dinitrogen Fixation by Beans

Abstract

The effect of phosphorus on nodulation, dry matter yield and dinitrogen fixation (as determined by the 15N technique) of bean plants (Phaseolus vulgaris) was evaluated in a field experiment at three growth stages. Application of phosphorus increased nodule mass, dry matter yield, nitrogen yield and dinitrogen fixation at all the three stages (i.e. flowering, pod-filling, and physiological maturity) but the effects of phosphorus were more pronounced at the flowering and pod filling stages. The highest dinitrogen fixation was recorded within the pod filling stage where phosphorus was applied. The results clearly demonstrate that availability of phosphorus can be an important factor in symbiotic biological nitrogen fixation by beans. For these studies the best sampling time appears to be within the pod-filling stage. A biological approach in solving phosphorus problems in symbiotic biological nitrogen fixation by grain legumes is suggested.