Developing a technique to quantify heterotrophic and autotrophic nitrification in acidic pasture soils.

摘要

A series of laboratory incubation experiments were conducted on soils from Maindample and Ruffy in northeast Victoria and from Whittlesea in the Plenty Valley, north of Melbourne, Victoria, Australia, to develop a technique for quantifying both autotrophic and heterotrophic nitrification in acidic pasture soils. The use of a specific inhibitor of the autotrophic ammonium oxidizers (N-serve) did not completely inhibit autotrophic nitrification in its commonly recommended concentrations (10 and 20 micro g g-1 soil) in these soils. The N-serve concentration, which completely inhibited autotrophic nitrification, was found to be 60-80 micro g g-1. Varying soil types, pHs, and organic-matter contents affected the optimum dose of N-serve required for complete inhibition of autotrophic nitrification. Mixing the inhibitor with the soil after application was also important for immediate inhibition of autotrophic nitrification. Using N-serve in combination with 15N-labeled glycine in the Maindample soil showed that heterotrophic organisms were using the organic route for nitrification, and N-serve did not affect heterotrophic nitrification. A lag of 12 to 24 h in complete inhibition of autotrophic nitrification by N-serve may have occurred suggesting nitrification studies using N-serve should include pre-incubation of the soils with N-serve for at least 1 day.