Acid phosphates, 196.

Adobe soils, 30.

After-cultivation, 158, 164.
benefits from, 164.
flat, 169.
frequency of, 167.
saves water, 164.
shallow, 15, 167, 169.
time for, 166.
tools for, 167.

Agencies active in making soils, 32.

Agents, with which farmer works, 5.
most important, 6.

Agriculture, foundation facts and principles of, 22.

Air, and the farmer, 5.
in relation to germination, 72.
necessary for root growth, 20.
work of, in making soils, 36.

Albuminoids in plants, 64, 66.

Alfalfa or lucern, 68.
roots, 13.
soils, 29.