Soils and Soil Management 



63 



three of the cans full to the upper edge with clean, dry sand or other 

 soil. Fill the remaining ones within one inch of the top. Weigh 

 the cans separately when dry, and add the 

 same amount of water to each one and note the 

 weight. Prepare the mulches as indicated below, 

 and weigh again. Set in a convenient place 



Fig. 38. Consuming soil moisture. Loss in seven days: A, packed surface, 

 8^ oz. water; B, fine chopped straw, 2 oz. water; C, covered with loose sand, 

 1 oz. water; D, dust mulch, 3 oz. water; E, young oat plants, 10 oz. water. 



where they will all be exposed to the same conditions. Weigh 

 daily for one week or ten days, and record the loss of weight for 

 each can on the following table. The difference in loss will approxi- 

 mate the power of these separate mulches to retard evapora- 

 tion from the surface. Give all the cans the same exposure to 

 light and wind. 



EFFECT OF MULCHES ON EVAPORATION 



