SOIL WATER 



87 



Exercise IV. — Water-holding capacity of soils. 



Materials. — Same as in Exercise III. 



Procedure. — When Exercise III is complete, cover chimneys and 

 allow all the free water to drain away. Then weigh the chimneys 

 and wet soil. The increased weight is water retained. Calculate 

 the percentage of water retained by each soil based on the weight 

 of the original sample. 



Write out a full description of the experiment and the points 

 of importance that it shows. 



Exercise V. — Moisture conservation by means of a soil mulch. 



Materials. — Three tumblers, one of which should be one inch 

 shorter than the other two, moist soil, dry clay loam and dry sand, 

 torsion balance. 



Procedure. — Fill the short tumbler level full with a well-mixed 

 moist soil. This is to serve as the unmulched treatment. Place 



CLAY LOAM MULCH 



5ANDY LOAM MULCH 



NO MULCH 



I 



MOI5T50IL 



MOIbT SOIL 



riOI6T50IL 



Fig. 18. — Tumblers filled with equal quantities of a moist soil and pre- 

 pared for a demonstration of the effectiveness of mulches in the conserva- 

 tion of moisture. Losses of moisture by evaporation are measured by weigh- 

 ing the tumblers. 



exactly the same amount of moist soil in each of the other tumblers 

 as is used in the shorter one, compacting to within one inch of the top. 

 On the surface of one place one inch of dry clay loam and on the 

 other one inch of dry sand. Weigh the tumblers now fully prepared. 



Set tumblers in a place of uniform temperature and weigh daily 

 for a week. The loss of weight each day is moisture. Tabulate 

 data and draw curves. 



Explain the significance of the results obtained. 



