Nitrification potential, dehydrogenase activity and microbial biomass in an argiudol soil cultivated with wheat under two tillering methods

Abstract

The purpose of this work was to analyze the dynamics of soil biomass and its activity in a soil fertilized with N andcultivated under conventional or zero tillage systems. The soil under conventional tillage had larger biomass than underzero tillage but, in this latter condition, it was further increased by the N-fertilization. Dehydrogenase activity inthe soil was identical under both management systems suggesting similar levels of activity. In addition, fertilizationdid not modify the nitrogen mineralization capacity of the soil. Only the addition of calcareous NH4NO3, a fertilizerthat releases nitrogen much faster than urea, resulted in the immobilization of nitrogen during wheat tillering, whereasurea did not alter soil N mineralization. The lack of a significant biomass response to tilling practices was reflectedby the wheat biomass and grain yield, that was the same under both tilling systems. Only the total N content of wheatwas higher under zero tillage than under conventional management, although this did not result in an increment ingrain yield.