

METHODS OF CULTIVATION j^g 



This shows a gain of nearly fifty per cent of soil moisture by 

 cultivation. 



Necessity of Adequate Cultivation. It has been very fully 

 demonstrated by California experience that adequate depth of tilth 

 must be attained. The depth of cultivation, or the thickness of 

 the dust-mulch, as some like to call it, must be sufficient to prevent 

 the access of the dry air to the firm soil below. At the East, where 

 they have a moister air, a thin mulch may answer; but in California, 

 with a thirsty air for such a protracted period, there must be 

 deeper tilth. Two or three inches of dust spread over a hard-pan 

 layer, formed in some soils by cultivation, will not retain moisture 

 well in California. The cultivator should go twice that depth, 

 ordinarily, and then the result will be accomplished if it is done 

 frequently enough to prevent the re-firming of the surface by 

 atmospheric moisture or by the rise of moisture from below. The 

 exact significance of depth in the loose, surface layer has also 

 been demonstrated by moisture determination in the subsoil at 

 different points by the California Experiment Station, as follows : 



Percentage of moisture in cultivated loam soil. 



Depth. Niles. Santa Maria. Ventura. 



Three inches 5.4 5.3 8.3 



Six inches 6.3 8.5 9.3 



These may be accepted, probably, as average results : Varia- 

 tion may occur in soils of different characters. The capillarity in 

 a heavy soil is vastly greater than in a light soil. The difficulty of 

 securing a pulverized surface layer is also .greater in the heavy 

 soil. The poorer the pulverization, the deeper the layer must be. 

 Naturally, then, growers' practice will vary. The rule will remain 

 that there must be depth enough to secure effective protection 

 of the firm soil beneath from agencies promoting evaporation. 



Loss of Moisture by Weed Growth. One of the most active 

 agencies for the exhaustion of moisture from the subsoil is the 

 growth of weeds. To cultivate the soil in winter and spring, and 

 then to allow a summer growth of weeds to "shade the soil" is 

 a great error. Although under the cover of rank weeds moisture 

 may appear even at the surface and convey the impression of 

 moisture-saving, the fact is, as fully demonstrated by experience 

 and actual experiment, the moisture in the lower layers of the 

 soil is reduced and trees are thus robbed of their supply. Weed 

 growth must be .resolutely suppressed during the dry season. 



Moisture Storage in the Soil. Conservation of moisture in the 

 soil is not only the surety of the current season's growth and 

 fruitfulness, but is the safeguard against injury from the years of 

 deficient rainfall which occur now and then in California. The 



