Influence of Inorganic Nitrogen on Nitrogen Fixation by Legumes as Revealed by N15¹

Synopsis N 15 ‐labeled fertilizer was used to determine the ratio of absorption of fixed vs. applied nitrogen by two legumes. Seedlings of both Ladino clover and alfalfa as well as established Ladino clover plants absorbed applied N fertilizer. Nitrogen fixation was reduced by nitrogen application, with the degree of reduction being definitely related to the amount of nitrogen applied.