THE CONTROL OF SOIL MOISTURE 283 



crop suffers. The amount of moisture conserved by a 

 mulch will usually keep the plant growing normally 

 through such periods, while crops on soils not so treated 

 may suflfer greatly. The tiding of crops over short periods 

 of light rainfall is the chief function of mulches in humid 

 climates. 



200. Other practices affecting evaporation losses. — 

 Although the control of water by mulches is such an 

 important consideration, other means of checking losses 

 are available. These may be grouped under five heads : 

 (1) fall and early spring plowing, (2) rolling, (3) shelters, 

 (4) level cultivation, (5) plants. 



201. Fall and early spring plowing. — Fall and early 

 spring plowing owe much of their efficiency to the con- 

 servation of moisture effected through the creation of a 

 mulch over the surface. Fall plowing may be practiced 

 for a number of reasons, but in regions of deficient rain- 

 fall, particularly in winter, the conservation of the mois- 

 ture in the soil at the close of the growing season is an 

 important consideration. This practice is well adapted 

 to those soils in semiarid sections that do not blow too 

 badly when fall-plowed, and where the winter rain is 

 not sufficient to saturate the soil. If the soil is left in 

 the bare, hard condition resulting from the removal of 

 a crop of maize, wheat, or barley, a large quantity of 

 water may be lost by evaporation during the fall months. 



For the average farmer in humid regions where the 

 winter rainfall is sufficient to saturate the soil, early 

 spring plowing, coupled with tillage, is very important. 

 Not only may moisture be conserved, but the soil is 

 worked at the stage when it yields most readily to pul- 

 verization. Fallow land, and bare stubble land of fine- 

 textured soil, are most benefited, since they become 



