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)

 

No. OF Trials

Water used per Ton of

Dry-Matter

Water Used

Dry-Matter per Acre

Acre-inch of Water per Ton of

Dry-Matter

(King)

   

tons

in.

tons

 

Barley ....

5

464.1

20.69

5.05

4.096

Oats ....

20

503.9

39.53

8.89

4.447

Maize ....

52

270.9

15.76

6.59

2.391

Clover . .

46

576.6

22.34

4.39

5.0899

Peas ....

1

477.2

16.89

4.009

4.212

Potatoes .

14

385.1

23.78

6.995

3.339

Average . .

 

446.3

23.165

5.987

3.939

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)

Water In The Soil 14

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 Ton

Tons of Water Lost

Acre-inch of Water Lost

Clover Hay...............................

1560

13.7

Air-dried corn fodder...............

570

5.0

Oats and straw..........................

1200

11.0

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)

Lawes and Gilbert England

Hellriegel Germany

WOLLNY

Germany

King Wisconsin

Beans .

214

Beans

262

Maize

233

Maize . .

272

Wheat . .

225

Wheat . .

359

Millet . .

416

Potatoes

423

Peas .

235

Peas .

292

Peas .

479

Peas .

447

Red clover .

249

Red clover .

330

Rape

912

Red clover .

453

Barley

262

Barley .

310

Barley .

774

Barley . .

393

   

Oats

402

Oats . . .

665

Oats . . .

557

   

Buckwheat.

371

Buckwheat.

664

   
   

Lupine . .

373

Mustard

843

   
   

Rye .

377

Sunflower .

490

   

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.