In these gulfs of moving unseen forms nitrification proceeds, and the rounds of life go on unceasingly.
"The Holy Earth"
L. H. Bailey
For the present, space is taken only to emphasize the value of decaying organic manures in the important matter of making plant food available; and attention is also called to the fact that the decomposition of the organic matter of the soil-including both fresh materials and old humus-is hastened by tillage and by underdrainage, which permit the oxygen of the air to enter the soil more freely, oxygen being a most active agent in nitrification and other decomposition processes of organic matter, as well as in the more common combustion of wood, coal, and so forth.
"The Farm That Won't Wear Out"
Cyril G. Hopkins
The need of nitrogen for grass in the early spring, before nitrification in the soil is active, is an illustration.
"Crops and Methods for Soil Improvement"
Alva Agee