Water occurs in. the soil in three forms: (1) Gravitational or hydrostatic water; (2) capillary water; (3) hygroscopic water.

Amount of water used by various crops in producing a ton of dry-matter (Stevenson)

Water In The Soil

Mean volume of water held by different soils, in laboratory tests in columns 45 inches high, with calculations to field conditions (Lyon and Fippin)

1 Estimated.

Water taken from the soil by evaporation is a loss additional to that transpired by the crop. The following results were secured at the Iowa Experiment Station in an experiment to determine the total amount of water removed from the soil by evaporation and transpiration : —

One inch of water covering an acre of land weighs about 226,875 pounds, or more than 113 tons.

Water evaporated by growing plants for one part of dry matter produced, in pounds (Lyon and Fippin)

Water needed under arid conditions.

Under dry-farming conditions, Widtsoe calculates that

1 acre-inch of water will produce 21/2 bu. wheat 10 acre-inches of water will produce 25 bu. wheat 15 acre-inches of water will produce 371/2 bu. wheat 20 acre-inches of water will produce 50 bu. wheat if all the water could be saved and be fully utilized in plant growth. Under average cultural conditions in arid regions, he concludes that approximately 750 pounds of water are required for the production of one pound of dry matter.