86 



ELEMENTS OF AGRICULTURE 



orated. Any loose mulch, like straw, on the surface of 

 the soil will accomplish this purpose. The capillary water 

 moves very slowly through dry soil, so that one of the 



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Fio. 44. Footprints kept moist and dark-colored by the rise of 

 capillary water 



best methods for preventing the evaporation is to form 

 a dust mulch on the surface. One of the great benefits 

 of cultivation is the formation of this dust mulch. When 

 possible, the soil should be cultivated after every rain as 

 soon as it is in proper condition for working. This culti- 

 vation will break up the crust, break the capillary connec- 

 tion, and prevent much of the evaporation. At the same 

 time it leaves the soil in a loose condition, ready for the 

 absorption of the next rain. 



When a moist soil is stirred, evaporation will first be 

 increased, but as the loose soil becomes dry it acts as a 



FIG. 45. A foot print. The particles are kept closer together and therefore 

 hasten the rise of water 



mulch to check evaporation. Hence, if rains are frequent, 

 cultivation may keep the soil drier. 



In most of the United States, the rainfall during the 

 growing months is not sufficient for the production of 



