Nitrification and nitrifying organisms in some Quebec soils.

The formation of nitrates in soil, under favourable conditions as to moisture, temperature, and aeration is a reaction well known and frequently studied. The bodies yielding nitric acid in the soil are, firstly, the various nitrogenous organic substances which arise from the decay of vegetable or animal matter; and secondly, ammonium salts, either produced in small quantity during the decay of organic matter, or carried to the soil by rain, or in some cases, applied as fertilizers. A further source of the nitrates contained in the soil is to be found in the free nitrogen of the atmosphere, but of any supply of this source, other than the ready-formed nitric acid contained in rain, and the nitrogen fixed by the nitrogen-fixing organisms, there is at present no substantial proof.[...