Effect of Nitrogen Fertilizers on the Nitrogenase Activity and Rhizosphere Microflora in Enterolobium timbouva Mart

Enterolohium timbouva Mart. Seedlings raised under pot culture conditions were given different nitrogen treatments viz. 20, 40, 60, 80, and 100 kg per ha in three equal splits at fifteen days interval after 50 days of sowing. Two controls without N aplication one with sterile (NO-1) and another with normal (NO-2) soils were also maintained simultaneously. Periodical samplings for nodule growth, nitrogenase (Acetylene reduction) activity and rhizospbere microflora was taken after every fifteen days interval after the application of the last nitrogen dose i.e. 85, 100, l15, 130 and 145 days after sowing. Among different N treatments, maximum and minimum nodule fresh and dry weights and nitrogenase activity was observed at N-40 and N-1OO respectively as compared to control in all the five growth stages. However. An increase in the rhizospbere microftora (bacteria and fungi) was observed with the increase in the nitrogen doses.