HOW MOISTURE IS CONSERVED 81 



soil has less capillarity than a heavy one. A sandy soil has less than 

 a clay, but both lose water by surface evaporation until, in an arid 

 climate, plants will die of thirst unless they be by nature drought 

 resisting. Garden vegetables are not of that character; in fact 

 quite the reverse. Consequently some means must be adopted to 

 prevent the moisture which is rising in the soil from reaching con- 

 tact with the outer air. This can be done by placing a covering 

 upon the compact portion of the soil so that the air shall not have 

 free access to it. Covering with a sufficient amount of almost any 

 coarse material, such as is commonly known as a mulch, will answer. 

 But the use of coarse manure or rotten straw or sawdust or any- 

 thing of that sort, is troublesome and expensive and otherwise 

 objectionable, although, it has an acknowledged place in garden 

 practice, as will be shown later. 



The Earth Mulch. California practice has made the widest 

 application of the truth that a finely pulverized surface layer of 

 sufficient depth is an effective mulch. Pulverizing the soil widens 

 the distance between its particles and consequently destroys its 

 capillarity until by the action of moisture, either in the form of 

 liquid or vapor, it becomes again compacted to a degree which re- 

 stores its power to transmit moisture. The cultivator has it then 

 within his power to spread a mulch and check evaporation simply 

 by fine and frequent pulverization of the surface layer by cultivation. 

 It is this ability which enables the California horticulturist to trans- 

 form the lower layers of his soil into a reservoir, and to profit by 

 the natural tendency of the moisture to rise in the compact soil until 

 it reaches the point where the pulverized layer checks its advance. 

 This practice makes possible an achievement which seems almost 

 incredible to workers in humid climates, viz. : the growing of a 

 succulent crop from seeding to harvest without the use of a drop 

 of water either by rain or irrigation, and it is this practice, coupled 

 with the deeper rooting habit of plants which is induced by it, which 

 enables our trees and field crops to grow thriftily and produce 

 heavily during months of drought, while a few weeks of drought 

 bring distress to plants in humid climates. 



But the pulverized surface layer must do more than arrest the 

 capillary rise of moisture before it reaches the surface : it must check 

 it at a point out of reach of the free entrance of air to the loose, 

 layer, consequently the degree of pulverization and the depth of 

 the loose layer are factors to be carefully observed. It is not enough 



