64 



APPLE GROWING IN CALIFORNIA. 



capillary action, by means of which the soil water is brought to the sur- 

 face and there evaporated, is checked. In other words, the soil is made 

 up of fine particles with spaces in between which become filled with 

 water. As a liquid in a fine tube will always travel upwards and reach 

 a level much higher than outside the tube, so in the soil we find the same 

 tendency, and we may conceive of the water as coming up through 

 myriads of little tubes which remain wide open to the surface unless 

 something is done to interfere with their continuity. Such interference 

 may be brought about by the use of the cultivator during the summer 

 season, when evaporation takes place so rapidly under ordinary condi- 

 tions ; but, as they will soon open up again after disturbance by the cul- 

 tivator, frequent cultivations are necessary, so that as fast as the mois- 



Fig-. 43. Well tilled orchard in Santa Cruz County. (Original) 



ture finds its way to the surface through these tubes, it is checked by 

 again breaking the capillarity. Figs. 42 and 43 show two well tilled 

 orchards in Humboldt and Santa Cruz counties. The ideal condition of 

 the soil to prevent evaporation is that of a dust mulch, which may be 

 maintained by working the soil with some type of harrow or cultivator 

 once a week. Some enthusiastic advocates of clean cultivation have 

 gone over their orchards even more frequently than this. 



Besides being a valuable means whereby moisture may be conserved, 

 cultivation is beneficial in keeping down weeds, and also places the soil 

 in the best possible condition for root development and the resultant 

 tree growth. It is a matter of common observation that orchards to 



