N2 Fixation by Grain Legume Varieties as Affected By Rhizobia Inoculation in The Sandy Loam Soil Of Sudano-Sahelian Zone of North Eastern Nigeria.

Rhizobium – legume symbiotic association contributes considerable amount of N in tropical soils. However, low rainfall and high temperature in Sudano-Sahelian region of Northeastern Nigeria may affect the Rhizobial population in the soil. Therefore, the influence of Rhizobia inoculation on N2 fixation by cowpea (Vigna unguiculata (L.) Walp.), groundnut (Arachis hypogaea L.) and bambara groundnut (Vigna subterranean L.Verdc.) was evaluated under field condition in Maiduguri. The seeds of the crops were inoculated with their Rhizobium strains and grown for 50 days, after which they were harvested and the amount of N fixed was measured. The results showed that rhizobia inoculation increased the amount of N fixed by 46% over the control. Cowpea differed significantly (

Effect of Phosphorus Fertilizer on Nitrogen Fixation by Some Grain Legume Varieties in Sudano – Sahelian Zone of North Eastern Nigeria

Nitrogen fixation by grain legumes contributes N to tropical soils. But in Sudano – Sahelian region of North-eastern Nigeria, low phosphorus content of the soil may restrict rhizobia population and legumes root development, which in turn, can affect their N2 fixing potential. A two- years field experiment was conducted at the Department of Soil Science Teaching and Research Farm University of Maiduguri North-eastern Nigeria during 2005 and 2006 cropping sessions to evaluate the influence of phosphorus (P) on N2 fixation by groundnut ( Arachis hypogaea L. ), cowpea (Vigna unguiculata L. ) and bambara groundnut (Vigna subterranean L. ). The legume crops and a sorghum variety (Paul Biya) were applied 0, 20 and 40 Kg Pha-1 and grown for 50 days, after which they were harvested and the amount of N fixed was determined. P fertilization significantly increased the amount of N fixed by the crops. Application of 40 KgPha-1 increased N fixation in cowpea, groundnut and bambara groundnut by 378, 169 and 138% respectively, over the control. Cowpea differed significantly from groundnut and bambara groundnut in the amount of N fixed (