Biomass Production, Tissue Nutrient Concentration, and N2-Fixing Potentials of Seven Tropical Leguminous Species

Abstract

Two pot experiments were conducted in the screenhouse of Forestry Research Institute of Nigeria, Ibadan (7° 30′ N and 3° 54′ E), southwestern Nigeria, to assess seven nitrogen-fixing shrub and tree legumes (NFTs) for their biomass production, N2-fixing potentials, and tissue nutrient concentration in two soil types. The purpose of the study was to identify an NFT that has the greatest potential for agroforestry alley cropping system and biochar production for sustainable soil productivity and crop production. The results indicated that plant growth rate, biomass production, and N2-fixing potential of the plants differed significantly with plant species but not with soil types, while the concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) in plant tissues, in most cases, varied significantly with plant species, plant parts, and soil types. Total biomass was greatest for Gliricidia sepium in both Ultisol and Alfisol, whereas Acacia auriculaeformis produced the smallest biomass in both soils. Gliricidia sepium and Leucaena leucocephala had the least %NdfF (percent N derived from fertilizer), 4.8 and 4.2, respectively, in the two soils, whereas Faidherbia albida and Acacia auriculaeformis had the highest %NdfF of 9.6 in the Ultisol and 7.4 in the Alfisol respectively. Significant negative correlations were established between plant biomass and %NdfF in the Ultisol (−0.888**) and Alfisol (−0.898**). Based on total biomass, shoot N concentration and %NdfF, the NFTs were ranked with Gliricidia rated highest in the two soils as having the greatest potential for alley cropping and biochar production, closely followed by Leucaena, while Acacia auriculaeformis had the lowest potential in both soil types.