In the Utah investigations it was found that of the water which fell as rain and snow during the winter, as high as 95-1/2 per cent was found stored in the first eight feet of soil at the beginning of the growing season.  Naturally, much smaller percentages were also found, but on an average, in soils somewhat dry at the beginning of the dry season, more than three fourths of the natural precipitation was found stored in the soil in the spring.  The results were all obtained in a locality where the bulk of the precipitation comes in the winter, yet similar results would undoubtedly be obtained where the precipitation occurs mainly in the summer.  The storage of water in the soil cannot be a whit less important on the Great Plains than in the Great Basin.  In fact, Burr has clearly demonstrated for western Nebraska that over 50 per cent of the rainfall of the spring and summer may be stored in the soil to the depth of six feet.  Without question, some is stored also at greater depths.

All the evidence at hand shows that a large portion of the precipitation falling upon properly prepared soil, whether it be summer or winter, is stored in the soil until evaporation is allowed to withdraw it Whether or not water so stored may be made to remain in the soil throughout the season or the year will be discussed in the next chapter.  It must be said, however, that the possibility of storing water in the soil, that is, making the water descend to relatively great soil depths away from the immediate and direct action of the sunshine and winds, is the most fundamental principle in successful dry-farming.

The fallow

It may be safely concluded that a large portion of the water that falls as rain or snow may be stored in the soil to considerable depths (eight feet or more).  However, the question remains, Is it possible to store the rainfall of successive years in the soil for the use of one crop?  In short, Does the practice of clean fallowing or resting the ground with proper cultivation for one season enable the farmer to store in the soil the larger portion of the rainfall of two years, to be used for one crop?  It is unquestionably true, as will be shown later, that clean fallowing or “summer tillage” is one of the oldest and safest practices of dry-farming as practiced in the West, but it is not generally understood why fallowing is desirable.

Considerable doubt has recently been cast upon the doctrine that one of the beneficial effects of fallowing in dry-farming is to store the rainfall of successive seasons in the soil for the use of one crop.  Since it has been shown that a large proportion of the winter precipitation can be stored in the soil during the wet season, it merely becomes a question of the possibility of preventing the evaporation of this water during the drier season.  As will be shown in the next chapter, this can well be effected by proper cultivation.