There is no good reason, therefore, for believing that the precipitation of successive seasons may not be added to water already stored in the soil.  King has shown that fallowing the soil one year carried over per square foot, in the upper four feet, 9.38 pounds of water more than was found in a cropped soil in a parallel experiment; and, moreover, the beneficial effect of this. water advantage was felt for a whole succeeding season.  King concludes, therefore, that one of the advantages of fallowing is to increase the moisture content of the soil.  The Utah experiments show that the tendency of fallowing is always to increase the soil-moisture content.  In dry-farming, water is the critical factor, and any practice that helps to conserve water should be adopted.  For that reason, fallowing, which gathers soil-moisture, should be strongly advocated.  In Chapter IX another important value of the fallow will be discussed.

In view of the discussion in this chapter it is easily understood why students of soil-moisture have not found a material increase in soil-moisture due to fallowing.  Usually such investigations have been made to shallow depths which already were fairly well filled with moisture.  Water falling upon such soils would sink beyond the depth reached by the soil augers, and it became impossible to judge accurately of the moisture-storing advantage of the fallow.  A critical analysis of the literature on this subject will reveal the weakness of most experiments in this respect.

It may be mentioned here that the only fallow that should be practiced by the dry-farmer is the clean fallow.  Water storage is manifestly impossible when crops are growing upon a soil.  A healthy crop of sagebrush, sunflowers, or other weeds consumes as much water as a first-class stand of corn, wheat, or potatoes.  Weeds should be abhorred by the farmer.  A weedy fallow is a sure forerunner of a crop failure.  How to maintain a good fallow is discussed in Chapter VIII, under the head of Cultivation.  Moreover, the practice of fallowing should be varied with the climatic conditions.  In districts of low rainfall, 10-15 inches, the land should be clean summer-fallowed every other year; under very low rainfall perhaps even two out of three years; in districts of more abundant rainfall, 15-20 inches, perhaps one year out of every three or four is sufficient.  Where the precipitation comes during the growing season, as in the Great Plains area, fallowing for the storage of water is less important than where the major part of the rainfall comes during the fall and winter.  However, any system of dry-farming that omits fallowing wholly from its practices is in danger of failure in dry years.

Deep plowing for water storage