The phenomenon of nitrification (see BACTERIOLOGY, AGRICULTURE and MANURE), i.e.
This result is partly due to their period of accumulation and growth extending even months after the period of collection by the ripening cereals has terminated, and at the season when nitrification within the soil is most active, and the accumulation of nitrates in it is the greatest.
Several conditions must be fulfilled before nitrification can occur.
In summer, when the temperature is about 24° C. (75° F.), nitrification proceeds at a rapid rate.
The presence of a base such as lime or magnesia (or their carbonates) is also essential, as well as an adequate degree of moisture: in dry soils nitrification ceases.