RETENTION OF WATER. BY MULCHES 



199 



cable, and of giving a few relatively large applications 

 rather than many small ones, in the artificial addition 

 of water. 



Surface evaporation may be reduced in two ways: 

 (1) By the application of some protective covering 

 to the moist soil. (2) By such surface treatment as will 

 reduce the tendency to evaporation. 



95. Mulches. The protective covering constitutes 

 a mulch. That is. a mulch is any material applied to the 



Fig. 62. Two types of soil structure . On the right, compact soil, clue 

 to the use of the roller. On the left, the same soil, loosened at the surface to 

 form a mulch. 



surface primarily for the purpose of preventing evapo- 

 ration. It may at the same time fulfil other useful 

 functions, as keeping down weeds and maintaining a 

 more uniform soil temperature, but its primary use is 

 to prevent evaporation. Of course, in so far as the 

 growth of weeds is prevented, moisture loss from that 

 source is eliminated, and at the same time plant food 

 is conserved for the regular crop. 



Mulches are of two sorts: (1) Foreign material 



