t deep. If one boring twelve inches deep does not give sufficient
soil make another boring or two close by and put all into the jar.

Take the sample, by whatever method obtained, weigh out ten or twenty
ounces of the moist soil and dry it at a temperature just below 212
degrees. When it is thoroughly dry weigh again. The difference between
the two weights will be the amount of water held by the sample. Now
divide this by the weight of the dry sample and the result will be the
per cent. of water held by the soil.

Several samples taken from different parts of the field will give an
average for the field. Repeat this every week or oftener through the
season and an approximate estimate of the water-holding capacity of
the soil will be obtained and consequently an indication of the crops
to which the soil is best adapted.

EXAMPLE.
Weight of a soil sample, 20 ounces.
When dried this sample weighs 173/4 ounces.
20 - 173/4 = 21/4, the water held by the soil.
2.25 / 17.75 = .12 plus.

This soil held a little over twelve per cent. of water. If this soil
continues to give about the same result for successive tests during
the growing season, the results would indicate a soil adapted to
cotton, late truck or corn.

CHAPTER XVIII

THE AFTER-CULTIVATION OF CROPS

The term "after-cultivation" is here used in referring to those
tillage operations which are performed after the crop is planted.
Synonymous terms are "cultivation," "inter-tillage," "working the
crop."

After-cultivation influences the texture, ventilation, heat, plant
food and moisture factors of fertility, but most particularly the
moisture factor.

Under ordinary circumstances the greatest benefit derived from
after-cultivation when properly performed is the saving of soil water
for the use of the crop.

LOSS OF WATER BY EVAPORATION

Soil water is seldom at rest unless the soil be frozen solid. When
rain falls on a fertile soil there is a downward movement of water.
When the rain ceases, water begins to evaporate from the surface of
the soil. Its place is taken by water brought from below by
capillarity. This is in turn evaporated and replaced by more from
below. This process continues with greater or less rapidity according
to the dryness of the air and the compactness of the soil.

LOSS OF WATER THROUGH WEEDS

We learned in a former chapter that during their growth farm plants
require an amount of water equal t