88 



WATER IN SOILS 



very heavy packers, rain water will be prevented from percolating 

 so readily and much of the rainfall may thus be held among soil 

 particles within a few inches or a few feet of the surface. Such 

 management of arid soils is known as " sub-surf ace packing." 

 The packers used for this purpose are heavy roils of some form 

 with a rough surface. Three main types are in use: Some have a 

 number of heavy cast wheels with tluted rims ; some have a number 

 of heavy cast wheels with V-shaped rims; some have ribbed sur- 

 faces made with iron pipes or bars. 



CONSERVATION OF MOISTURE 



Since much of the rain water which falls in a given region is 

 lost by surface run-off, or by evaporation, and by rapid percola- 



FIG. 67. The Acme harrow is a good clod crusher. When the soil surface becomes pulver- 

 ized the moisture is conserved. 



tion; and since there is much suffering from droughts, even in 

 humid regions, it is essential that every practical means be used 

 to save the moisture which falls during wet seasons. Among the 

 sources of loss of moisture which are largely within] the control 

 of the farm manager, are: (1) evaporation through baked and 

 crusty soils; (2) run-off is increased by bad management; (3) the 

 growth of weeds; (4) reduction of the humus content of soils; (5) 

 failure to loosen packed soils; (6) failure to pack loose soils; (7) 

 failure to check winds. 



