Organic matter, heterotrophic activity, and NO. consumption in soils

When the effect of water content was minimized, soil CO2 evolution and soil organic matter content were good predictors of aerobic NO. uptake rate constants across a wide range of soil types. Field manure application to a Gleysol stimulated NO. uptake rate constants and lowered NO. compensation points compared to unfertilized or NH4NO3-fertilized soil. This effect lasted for months after manure application. In a laboratory experiment, addition of manure reduced the NO. efflux associated with nitrification of NH4Cl fertilizer, and manured soils had a greater capacity to remove NO. from polluted air. Evidence is presented that these observations result from NO. oxidation during heterotrophic microbial activity in soil.