Influence of Urease and Nitrification Inhibitors on Ammonium and Nitrate Supply and the Soil Microbial Population in Western Canadian Soils
Luca, C., J. Germida, J. Schoenau and P. Qian. 2004. Soils and Crops Conference Proceedings
Abstract
Improving nitrogen use efficiency and limiting losses of N from the soil system is important both
economically and environmentally. This study assessed the potential of using a urease inhibitor,
Agrotain, or a nitrification inhibitor, nitrapyrin, to create a slow release effect similar to that
found in sulfur coated urea in Western Canadian soils of the Brown and Black soil zones. The
nitrapyrin significantly reduced the cumulative NO3-
supply to the point of inhibition of
nitrification for 21d in the Brown soil, but had little effect on the Black soil. Nitrapyrin had little
effect on the supply of NH4
in both soils. The Agrotain had some effect on NO3-
- supply and
significantly reduced the NH4
supply for 14d in the Brown soil. Differences between the two
soils were consistent with results in other studies and attributed to pH and organic matter content
differences. The total heterotrophic and Nitrosomonas microbial populations were enumerated
using spread plates and most probable number assays. It was concluded that Agrotain had little
effect on the microbial population, where as nitrapyrin reduced Nitrosomonas populations and
increased total heterotrophic counts in both soils. Similarity between the results in this study and
the literature suggest that the soils in Western Canada have similar responses to inhibitors as
those characterized by the literature. Therefore, whether improved nitrogen use efficiency from
the use of inhibitors in wheat in Western Canada would be large enough to justify the used of
inhibitors will depend on whether local soil properties are conducive to promote volatilization,
leaching and denitrification losses of N.
Key Words
Agrotain®, nitrapyrin, ammonium and nitrate supply, Nitrosomonas
