Soil Regulates Circulation of Water on the Planet Earth - Soil: The Skin of the Planet Earth - page 140

Fig. 10.6 Soil water content profi les due to redistribution at the end of infi ltration. This time is
denoted by time zero, t 0 , when the depth of infi ltration front is denoted by z f . Then there is no water
infl ow at the soil surface, but the water content is decreased since the top wet part is drained and
the water from this drained part fl ows downward to the originally dry subsoil. The volume of
drained water from the infi ltration I d equals the volume of water wetting the soil below the infi ltra-
tion front I w , i.e., the volume of water in redistribution. All is valid provided that evaporation from
the soil does not exist. Here again t 0 < t 1 < t 2
time of those fi rst studies at the end of nineteenth century, the term “capillary capac-
ity” was also used; see also Sect. 9.1 . There were relatively simple methods on how
to determine the value of “fi eld” or “capillary” capacity in the laboratory on undis-
turbed core samples having a volume of about 100-200 cm 3 . Soil samples, each
kept in a rigid cylinder, were fi rst completely saturated with water and subsequently
drained either on a thick layer of dry sand or on multiple fi ltering paper. The amount
of water retained after such a simple drainage procedure was considered a reliable
measure of fi eld or capillary capacity. Since the empirically found rough estimate of