Influence of P Fertilization on Biological Nitrogen Fixation in Herbaceous Legumes Grown in Acid Savannah Soils from the Tabasco State, Mexico

gThe use of leguminous plants in the agricultural systems of the humid tropics is an alternative means for providing N to soils considered unfertile and marginal. The objective of this study was to assess the biological nitrogen fixation (BNF) in the symbiosis Rhizobia-herbaceous legumes (Mucuna deeringiana, Canavalia ensiformis, Vigna umbellata, Cajanus cajan, Dolichos lablab, Arachis pintoi and Crotala-riajuncea) grown in acid soil amended with P fertilizer by the 15N-isoto-pic dilution technique (“A”-value) using maize, Brachiaria spp. and no nodulating common bean as reference crops. Results indicate a positive effect of P-fertilizer on parameters associated with BNF and biomass accumulation. The legumes Cajanus cajan and Canavalia ensiformis showed good performance in terms of dry weight of nodules (C. cajan = 758 and C ensiformis = 500 mg nodules plant−1 with 49 and 56 nodules plant−1, respectively) at flowering stage, and BNF (C. cajan = 170 and C ensiformis = 366 kg N ha−1 cycle−1) when 8...