Conserving Soil Moisture. 



187 



It should be understood, however, that if the water 

 reservoirs had been much farther below the surface of the 

 soil, and below the mulch, the mulches would have been 

 more effective as well as less water would have been lost 

 from the unmulched cylinders. 



218. Frequency of Cultivation May Make Mulches More 

 Effective. When a fresh mulch is formed upon the surface 

 of a well moistened soil the first effect of the stirring is 



IT 





B 



FIG. 5$. Apparatus for measuring the relative effectiveness of mulches. 



to increase the rate of evaporation from the field, on ac- 

 count of the much larger surface of wet soil which is ex- 

 posed to the air. This greater loss of water, however, is 

 largely from the stirred soil. If dry winds and sunny 

 weather follow the formation of the soil mulch it soon 

 becomes so dry that but a relatively small amount of wa- 

 ter can pass up through it. On the other hand if a series 

 of cloudy days follow, when the rate of evaporation 

 must be small even from firm wet soil, and if at the same 

 time the soil below the mulch is quite moist, so much water 

 may pass up into the mulch as to nearly saturate the 

 lower portion of it and to cause the kernels to be drawn 



