Phulai (Acacia modesta) is a widely distributed species in northern Pakistan. It has high forage and fuel wood value. Its nitrogen contributing potential to soil was studied at Lohi Behr Range. Soil samples were taken under and outside of the canopy of phulai trees at various depths. Significantly higher nitrogen content was observed under the canopy. A general trend of decreasing nitrogen with depth was found. Two soil series did not show much difference in nitrogen content. Key words: Phulai, Soil, Nitrogen Fixation, Legumes.