Effect of Phosphorus Fertilisation on Legume Nodule Formation and Biomass Production in Mount Kenya Region

ABSTRACT The response of legumes to the application of phosphorus was tested in the upper midland 3 agro-ecological zone in a humic Nitisol at Karurina Location of Embu District in the central Kenya region. The legumes tested were Mucuna pruriens, Canavalia ensiformis, Glycine max, Crotalaria ochroleuca and Lablab purpureus. A split plot design was used in which 17 kg/ha phosphorus was applied to half of the plot and the remainder was planted without any P. Nodulation and biomass assessment were conducted at the respective flowering stages for each of the legumes tested. The results revealed that all legume species tested formed effective nodules at either the tap root or the lateral roots. Crotalaria showed the highest level of nodule formation whereas Canavalia formed one or no nodules per plant. Mucuna showed the highest level (4.13 t/ha) of biomass accumulation while Canavalia gave the lowest (0.56 t/ha) amount of biomass. Addition of phosphorus did not affect nodulation or biomass accumulation in any of the legume species tested.