DRAINAGE, IRRIGATION, AND DRY FARMING 129 



156. Conserving moisture. In dry farming it is necessary to 

 choose a soil that has capacity to absorb water rapidly and to 

 hold it well. A heavy clay soil absorbs water too slowly, packs 

 upon drying, and is so difficult to work that it is unsatisfactory 

 for dry farming. A sandy soil especially when the subsoil is 

 very sandy absorbs water readily, but permits water to percolate 

 so deeply that it passes beyond the reach of the roots of plants. 

 Soils that are shallow or have hardpan layers in the upper 

 subsoil are unsatisfactory because such soils do not permit of 

 deep root growth. An ideal dry-land soil is a sandy or silty 

 loam that has a uniform texture to a depth of from ten to fifteen 

 feet. A soil of this character absorbs water rapidly, retains it 

 well, and permits the roots of plants to grow deeply, all of which 

 characteristics are essential to success in dry farming. 



In handling soils under dry farming two facts should be con- 

 stantly kept in mind : first, during the rainy season the soil 

 should be kept in such condition that the largest possible quan- 

 tity of the rainfall will be absorbed and held by the soil ; and 

 second, the methods of cultivation should be such as to pre- 

 vent as fully as possible the loss of water by weed growth and 

 by evaporation. In the Pacific coast states it is advisable to 

 plow deep in the late fall so that the soil will absorb the rain 

 that falls during the winter months (Figs. 55 and 56). In the 

 Intermountain states the plowing should be done in the early 

 spring, while in the Great Plains states the ground should be 

 double-disked early in the spring and plowed in the early summer. 

 The cultivation following plowing in all areas should be such as 

 will prevent weed growth. The disk and the harrow may be 

 used for cultivation in the Intermountain region, where high 

 winds are not common, but in the Great Plains region, where 

 there is danger of the soil blowing, cultivation should be done 

 with a shovel cultivator, spring-tooth harrow, or other implement 

 that leaves the surface rough and the soil cloddy. 



157. Summer fallow. Where the rainfall is too light to in- 

 sure a profitable crop each season, as is the condition over much 

 of the dry-land region, summer fallowing is practiced. Summer 



