Soil fertility is the capacity of soil to supply essential nutrients and water to plants in adequate amounts and proportions for optimum growth and yield. Leguminous trees and shrubs can enhance soil fertility by adding N through N2 fixation and recycling nutrients through pruning. Therefore, this study assessed the nutrients of some nitrogen fixing trees and shrubs’ foliage in Federal University of Agriculture, Abeokuta, Nigeria with the view of assessing their potentials for incorporation into agroforestry system. The selected leafy biomass for this study is of Parkia biglobosa, Leucaena leucocephala, Gliricidia sepium, Cajanus cajan, Piliostigma thonningii, and Jatropha curcas. The data were analyzed using analysis of variance (ANOVA), and means were separated using Fisher's Least Significant Difference (LSD) at P = 0.05. For the results, G. sepium was observed to have significant higher values (27.68 g kg-1 and 9.66 g kg-1) of nitrogen and organic carbon, lower values (2.87 g kg-1, 138.00 g kg-1, 2.01 g kg-1, 1.04 g kg-1, 1.54 g kg-1, 201.20 g kg-1, and 187.80 g kg-1) of carbon to nitrogen ratio (C: N), lignin (L), lignin to nitrogen ratio (L: N), polyphenol to nitrogen ratio (PP: N), lignin plus polyphenol to nitrogen ratio (L+PP): N, acid detergent fibre (ADF) and cellulose respectively. The results also revealed that G. sepium, among other species, had highest values (27.68 g kg-1, 306.78 mg kg-1, 3167.01 C mol kg-1, and 461.38 C mol kg-1) in nitrogen, phosphorus, potassium, and magnesium respectively. The correlation coefficients of these essential nutrients were in a state of dynamic equilibrium. In conclusion, G. sepium contains a superior chemical composition and primary and secondary nutrients that can promote rapid decomposition of the leaves and higher release of nutrients. Therefore, it is recommended for soil replenishment and crop improvement strategies.