It is a very common experience, in the
arid region, that great, deep cracks form during hot weather. From
the walls of these cracks evaporation goes on, as from the topsoil,
and the passing winds renew the air so that the evaporation may go
on rapidly. The dry-farmer must go over the land as often as needs
be with some implement that will destroy and fill up the cracks that
may have been formed. In a field of growing crops this is often
difficult to do; but it is not impossible that hand hoeing,
expensive as it is, would pay well in the saving of soil moisture
and the consequent increase in crop yield.
How soil water reaches the surface
It may be accepted as an established truth that the direct
evaporation of water from wet soils occurs almost wholly at the
surface. Yet it is well known that evaporation from the soil surface
may continue until the soil-moisture to a depth of eight or ten feet
or more is depleted. This is shown by the following analyses of
dry-farm soil in early spring and midsummer. No attempt was made to
conserve the moisture in the soil:--
Per cent of water in Early spring Midsummer
1st foot 20.
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