6o 



THE PHYSICAL PROPERTIES OF SOILS 



ELEVENTH EXERCISE 



EFFECT OF MULCHES UPON THE RATE 



OF EVAPORATION 



Mulching the soil either by earth mulches (tillage) 

 or by artificial mulches (straw or 

 manure) is the most effective means 

 of conserving soil moisture. 



Fill five galvanized iron cylinders 

 (T) to within one-half inch of the 

 top with the same soil, compacting 

 uniformly. Fill the water-jackets 

 and apply pressure until the mois- 

 ture appears on the surface of each 

 soil. Remove the water from the 

 jackets and treat the surfaces of the 

 cylinders as follows: 



/ 



i 



MULCH CYLINDER 

 Sectional View 



No. I — No treatment. 



No. 2 — Cultivate one inch deep each day. 



No. 3 — Compact the surface. 



No. 4 — Remove the surface inch of soil and 

 replace with sand. 



No. 5 — Remove the surface inch of soil and 

 replace with cut straw. 



Care must be taken to have the finished surface of 

 the soil in all of the cylinders at exactly the same dis- 

 tance below the rim, and to expose all of the cylinders 

 to the same atmospheric conditions. 



