Importance of a moist subsoil

In the consideration of the downward movement of soil-water it is to be noted that it is only when the soil is tolerably moist that the natural precipitation moves rapidly and freely to the deeper soil layers.  When the soil is dry, the downward movement of the water is much slower and the bulk of the water is then stored near the surface where the loss of moisture goes on most rapidly.  It has been observed repeatedly in the investigations at the Utah Station that when desert land is broken for dry-farm purposes and then properly cultivated, the precipitation penetrates farther and farther into the soil with every year of cultivation.  For example, on a dry-farm, the soil of which is clay loam, and which was plowed in the fall of 1904 and farmed annually thereafter, the eighth foot contained in the spring of 1905, 6.59 per cent of moisture; in the spring of 1906, 13.11 per cent, and in the spring of 1907, 14.75 per cent of moisture.  On another farm, with a very sandy soil and also plowed in the fall of 1904, there was found in the eighth foot in the spring of 1905, 5.63 per cent of moisture, in the spring of 1906, 11.41 per cent of moisture, and in the spring of 1907, 15.49 per cent of moisture.  In both of these typical cases it is evident that as the topsoil was loosened, the full field water capacity of the soil was more nearly approached to a greater depth.  It would seem that, as the lower soil layers are moistened, the water is enabled, so to speak, to slide down more easily into the depths of the soil.

This is a very important principle for the dry farmer to understand.  It is always dangerous to permit the soil of a dry-farm to become very dry, especially below the first foot.  Dry-farms should be so manipulated that even at the harvesting season a comparatively large quantity of water remains in the soil to a depth of 8 feet or more.  The larger the quantity of water in the soil in the fall, the more readily and quickly will the water that falls on the land during the resting period of fall, winter, and early spring sink into the soil and move away from the topsoil.  The top or first foot will always contain the largest percentage of water because it is the chief receptacle of the water that falls as rain or snow but when the subsoil is properly moist, the water will more completely leave the topsoil.  Further, crops planted on a soil saturated with water to a depth of 8 feet are almost certain to mature and yield well.

If the field-water capacity has not been filled, there is always the danger that an unusually dry season or a series of hot winds or other like circumstances may either seriously injure the crop or cause a complete failure.  The dry-farmer should keep a surplus of moisture in the soil to be carried over from year to year, just as the wise business man maintains a sufficient working capital for the needs of his business.  In fact, it is often safe to advise the prospective