90 DRY LAND FARMING 



The measures that may be adopted to prevent or 

 at least to lessen the escape of soil moisture include the 

 following: (1) The maintenance of a dust mulch on 

 land that is being fallowed; (2) the stirring or cultivat- 

 ing of the soil that has been sown or planted, and (3) 

 the artificial shading of the soil. 



A dust or soil mulch is a dry layer of earth cover- 

 ing the surface of the soil. It is formed by pulverizing 

 the surface after the land has been plowed. It may also 

 be formed by discing stubble land in the autumn or 

 spring, and by stirring fall-plowed land in the early 

 spring, that has settled upon itself. The implement 

 chiefly used in making it is the spike-tooth harrow, but 

 on cloddy soils the aid of the roller or the planker may 

 be called in. On hard surfaces the disc should precede 

 the harrow. The process is frequently spoken of as sum- 

 mer tillage. The depth of the mulch is from 2 to 3 

 inches. The fineness of the same is dependent to some 

 extent on the character of the soil. On some soils, espe- 

 cially those that are granular, it does not readily become 

 too fine. On others, as fine clays, the excessive use of 

 the harrow may make the soil so fine that it is not readily 

 penetrated by rain. In clay soils covered with a dust 

 mulch, the loss by evaporation is greater than in those 

 covered by a mulch of coarse particles, as coarse sand, 

 for the reason that water climbs more readily in fine than 

 in coarse soil particles. 



Rain is the chief agent in destroying the efficiency 

 of the dust mulch. It does so: (1) by tending to restore 

 the pore connections between the dust mulch and the 

 soil below, and (2) by the numerous cracks which fol- 

 low in many soils from -the rapid drying of a more or 

 less impacted surface. It is greatly important that the 

 soil mulch shall be renewed after rains, and especially 

 after heavy rain in many of the soils of the west. The 

 aim should be to make such renewal at the most pro- 



