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

Abstract

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 N 2 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 N 2 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 (P<0.05). Cowpea fixed (54.19 KgNha -1), groundnut (39.16 KgNha -1) and bambara groundnut fixed (28.42 KgNha -1). Cultivation of Bornoji red cowpea variety with application of 40 KgPha -1 would improve the soil N status.