aided by plowing, 146.
aided by lime, 146.
conditions favorable to, 146.

Nitrifying germs, 144, 145.

Nitrogen, 66.
added to the soil by legumes, 68.
grown on the farm, 68.
in humus, 167.
in soils, 67, 148.
in plants, 66, 67.
in fertilizers, 192.
loss of, 67.
sources of, 171.

Nitrogen-fixing germs, 144.

Non-leguminous green manure-crops, 191.

Norfolk sand, 28.


Oats, soil for, 29.

Object of this book, 3.

Odorless phosphate, 198.

Oil in plants, 64, 66.