Well-fallowed soil is in an ideal condition for admitting
oxygen.
If the temperature is right, germination begins by the forcible
absorption of water by the seed from the surrounding soil. The force
of this absorption is very great, ranging from four hundred to five
hundred pounds per square inch, and continues until the seed is
completely saturated. The great vigor with which water is thus
absorbed from the soil explains how seeds are able to secure the
necessary water from the thin water film surrounding the soil
grains. The following table, based upon numerous investigations
conducted in Germany and in Utah, shows the maximum percentages of
water contained by seeds when the absorption is complete. These
quantities are reached only when water is easily accessible:--
Percentage of Water contained by Seeds at Saturation
German Utah
Rye 58 --
Wheat 57 52
Oats 58 43
Barley 56 44
Corn 44 57
Beans 95 88
Lucern 78 67
Germination itself does not go on freely until this maximum
saturation has been reached. Therefore, if the moisture in the soil
is low, the absorption of water is made difficult and germination is
retarded.
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