So vitally important is a permanent soil mulch for the conservation for plant use of the water stored in the soil that many attempts have been made to devise means for the effective cultivation of land on which small grains and grasses are growing.  In many places plants have been grown in rows so far apart that a man with a hoe could pass between them.  Scofield has described this method as practiced successfully in Tunis.  Campbell and others in America have proposed that a drill hole be closed every three feet to form a path wide enough for a horse to travel in and to pull a large spring tooth cultivator’ with teeth so spaced as to strike between the rows of wheat.  It is yet doubtful whether, under average conditions, such careful cultivation, at least of grain crops, is justified by the returns.  Under conditions of high aridity, or where the store of soil-moisture is low, such treatment frequently stands between crop success and failure, and it is not unlikely that methods will be devised which will permit of the cheap and rapid cultivation between the rows of growing wheat.  Meanwhile, the dry-farmer must always remember that the margin under which he works is small, and that his success depends upon the degree to which he prevents small wastes.

Dry-farm potatoes, Rosebud Co., Montana, 1909.  Yield, 282 bushels per acre.

The conservation of soil-moisture depends upon the vigorous, unremitting, continuous stirring of the topsoil.  Cultivation! cultivation! and more cultivation! must be the war-cry of the dry-farmer who battles against the water thieves of an arid climate.

CHAPTER IX

REGULATING THE TRANSPIRATION

Water that has entered the soil may be lost in three ways.  First, it may escape by downward seepage, whereby it passes beyond the reach of plant roots and often reaches the standing water.  In dry-farm districts such loss is a rare occurrence, for the natural precipitation is not sufficiently large to connect with the country drainage, and it may, therefore, be eliminated from consideration.  Second, soil-water may be lost by direct evaporation from the surface soil.  The conditions prevailing in arid districts favor strongly this manner of loss of soil-moisture.  It has been shown, however, in the preceding chapter that the farmer, by proper and persistent cultivation of the topsoil, has it in his power to reduce this loss enough to be almost negligible in the farmer’s consideration.  Third, soil-water may be lost by evaporation from the plants themselves.  While it is not generally understood, this source of loss is, in districts where dry-farming is properly carried on, very much larger than that resulting either from seepage or from direct evaporation.  While plants are growing, evaporation from plants, ordinarily called transpiration, continues.  Experiments performed in various arid districts have shown that one and a half to three times more water evaporates from the plant than directly from well-tilled soil.  To the present very little has been learned concerning the most effective methods of checking or controlling this continual loss of water.  Transpiration, or the evaporation of water from the plants themselves and the means of controlling this loss, are subjects of the deepest importance to the dry-farmer.