276 SOILS: PROPERTIES AND MANAGEMENT 



the same time it would become puddled on wetting — 

 certainly a very undesirable condition. As a matter of 

 fact, efficient mulches are not in a dust form, but are 

 granulated and much looser than could be obtained were 

 they finely divided. It is evident that the term " dust 

 mulch " is incorrect and should be superseded by " soil 

 mulch," a figure of speech which more exactly expresses 

 the true field conditions. 



194. Formation of a mulch. — It has already been 

 stated that a mulch should be formed as quickly as 

 possible. This would not be such a factor were the 

 mulch adjusted only once in a season. It is necessary, 

 however, especially in humid regions, to re-form a mulch 

 every week or ten days. The cutting-down of formation 

 losses therefore becomes important. In general the 

 mulch should be made just as soon after a rain as it is 

 possible to work the land, since the most rapid evapora- 

 tion occurs during the few hours immediately after a 

 rain, when the soil is very moist. Even after light showers 

 the soil should be quickly cultivated, since the rain may 

 have established a capillary communication with the 

 surface and thus provided for a rapid loss of the water 

 already conserved by previous work. Under arid con- 

 ditions, where the atmosphere is dry and hot and in free 

 circulation, the surface soil is quickly dried out after a 

 rain. This drying takes place so rapidly that the capil- 

 lary films quickly become so thin that movement is 

 stopped and no more water is brought to the surface. 

 The soil may be ever so hard and compact, but as long 

 as it is kept dry it very effectively conserves the moisture 

 below. The more rapid the loss, the more quickly will 

 the mulch condition be created,, and therefore the less the 

 total loss of water is likely to be. This has been demon- 



