Biological nitrogen fixation of acacia drepanolobium

Abstract

To establish whether Acacia drepanolobium nodulates with indigenous rhizobia, 4 factorial experimental design was conducted under glasshouse conditions in soil collected from 3 sampling sites: black cotton, transition and red soil. The collection of soil and glasshouse experiments were conducted at Mpala eco-zone, Laikipia District, Kenya. This design allowed one to examine statistically the main effects of canopy distance, soil type, soil treatment and the interaction between these 4 factors. In each of the 3 example sites, soil was randomly sampled from 2 collection areas: below and away the canopies of A. drepanolobium. Each soil type was subjected to 4 treatments: Control, fertilization, sterilization and a combination of sterilization and fertilization. A. drepanolobium nodulated with rhizobia but the level of nodulation varied with soil type, soil treatment, canopy distance and the interaction between these 4 factors. Black cotton soil collected a way (3 meters) from the A. drepanolobium canopies had the highest nodulation.