We now turn to its beneficent aspect, its use in peace.
III
FEEDING THE SOIL
The Great War not only starved people: it starved the land. Enough
nitrogen was thrown away in some indecisive battle on the Aisne to save
India from a famine. The population of Europe as a whole has not been
lessened by the war, but the soil has been robbed of its power to
support the population. A plant requires certain chemical elements for
its growth and all of these must be within reach of its rootlets, for it
will accept no substitutes. A wheat stalk in France before the war had
placed at its feet nitrates from Chile, phosphates from Florida and
potash from Germany. All these were shut off by the firing line and the
shortage of shipping.
Out of the eighty elements only thirteen are necessary for crops. Four
of these are gases: hydrogen, oxygen, nitrogen and chlorine. Five are
metals: potassium, magnesium, calcium, iron and sodium. Four are
non-metallic solids: carbon, sulfur, phosphorus and silicon. Three of
these, hydrogen, oxygen and carbon, making up the bulk of the plant, are
obtainable _ad libitum_ from the air and water.
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