Hopkins in his study of the soils of Illinois
has repeatedly observed, in connection with certain soils, that
where the land is kept fertile, injury from drouth is not common,
implying thereby that fertile soils will produce dry matter at a
lower water-cost. The most recent experiments on this subject,
conducted by the Utah Station, confirm these conclusions. The
experiments, which covered several years, were conducted in pots
filled with different soils. On a soil, naturally fertile, 908
pounds of water were transpired for each pound of dry matter (corn)
produced; by adding to this soil an ordinary dressing of manure'
this was reduced to 613 pounds, and by adding a small amount of
sodium nitrate it was reduced to 585 pounds. If so large a reduction
could be secured in practice, it would seem to justify the use of
commercial fertilizers in years when the dry-farm year opens with
little water stored in the soil. Similar results, as will be shown
below, were obtained by the use of various cultural methods. It may
therefore, be stated as a law, that any cultural treatment which
enables the soil-water to acquire larger quantities of plant-food
also enables the plant to produce dry matter with the use of a
smaller amount of water.
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