greatest factor in growth of crop, 46.
importance of, 39, 151.
loss of, 53, 155, 157, 164.
loss of by evaporation, 54.
loss of by weeds, 54, 165.
loss of by surface wash, 53.
necessity for, 151.
not enough, 154.
saving, 165.
sources of, 40, 153.
too much, 154.

Soil water influenced,
by cropping, 159.
by harrowing, 101, 103, 158.
by humus, 42, 43, 44, 45, 220.
by plowing, 91, 156.
by ridging, 98, 158.
by rolling, 106, 158.

Sorghum soils, 162.

Soy-bean, as a green manure crop, 189.
growth of roots, 12.

Spade, 90.

Spading, 90.

Spading-fork, 90.