EXERCISE 13 

 SOIL MULCHES 



Object. To determine the amount of water that evap- 

 orates from the soil when cultivated at different depths 

 and when covered with different material. 



Explanation. A soil mulch is any covering placed upon 

 the soil that prevents the evaporation of moisture. There 

 are two kinds of soil mulches, natural soil mulches and arti- 

 ficial soil mulches. An artificial soil mulch is any material 

 such as straw, sawdust, or stones placed upon the soil to pre- 

 vent evaporation, while a natural soil mulch is the loosened 

 surface of the soil itself produced by cultivation. Natural 

 soil mulches are the most practical because they can usually 

 be produced at the smallest cost. Any implement of culti- 

 vation that leaves the surface soil loose and mellow will 

 produce a good natural soil mulch. 



Equipment. 1. Four evaporation cylinders. 



2. A wash pan. 



3. A long-bladed knife or spatula. 



4. Scales weighing to one quarter of a pound and having 

 a capacity of fifty pounds. 



5. A small amount of cut straw. 



Directions. Fill the four evaporation cylinders to within 

 one inch of the top with fine air-dried loam soil. 



Fill the water-supply tubes on the cylinders with water. 



53 



