Abstract

                                Greenhouse study was carried out on sandy clay loam soil (Typic Haplustall) of Coimbatore. Tamil Nadu to determine the amount of nitrogen fixed from the atmosphere by different species of Acacia by various methods by the application of nitrogenous and phosphatic fertilizers in combination with N. fixing organisms. The accuracy of various methods of N, fixation were evaluated and the results predicted that 'A' value technique was comparatively best suitable method for tree crops closely followed by dilution method. Among the four Acacia species. A. nilotica derived maximum amount of nitrogen from the atmosphere followed by 4. planifrons due to the application of " N urea (75%) + SSP (100%)+ Rhizobium + VAM.

Key words : Atmospheric nitrogen fixation, Different methods. Acacia species