92 DRY LAND FARMING 



and cultivator when applied to such crops as corn and 

 potatoes. The cultivation also seeks the destruction of 

 weeds, which will sap moisture from the soil more com- 

 pletely when they are allowed to grow numerously than 

 any other agency. So valuable and so effective are these 

 methods of maintaining soil moisture that in dry areas 

 they are practised on crops by growing them in rows 

 though not usually grown thus, as alfalfa for instance, 

 in order to make such cultivation possible. When ap- 

 plied to small grains, however, the yields have not been 

 found sufficient to justify the practise. 



Shading the soil and thus protecting it from evapo- 

 ration may be incidental or it may be designedly done. 

 It is incidental when it is the result of crop growth, as 

 when it is furnished by the cereals when too advanced 

 in growth to admit of harrowing them longer, by corn 

 and other cultivated crop's when the plants have attained 

 a considerable size, and by the high-cut stubbles of ma- 

 ture grain that has been harvested. It is done through 

 design when the soil or the crop is strewn with straw, 

 manure or some other substance. Such a method of pre- 

 venting the escape of moisture has been found effective 

 in a considerable degree when applied to orchard and 

 other trees, and even to grass lands. The reduction of 

 evaporation by a broad-leafed crop, as corn, when well 

 grown, is very considerable. 



Loss of soil moisture by transpiration. Soil mois- 

 ture may be lost, as previously intimated, in three ways, 

 viz.: (1) by leaching; (2) by evaporation, and (3) by 

 transpiration. The loss by leaching, as has been shown, 

 seldom occurs in dry areas. The loss by evaporation, of- 

 tentimes serious, has just been discussed. The loss by 

 transpiration through the leaves of plants is several 

 times greater than the loss that usually occurs by evapo- 

 ration. 



