MOISTURE IN THE SOIL 69 



use of this principle when he places a layer of leaves over 

 strawberries, potatoes, or any crop that he wishes to keep 

 well supplied with moisture. He calls such a layer of 

 leaves a mulch, which simply means a cover to protect the 

 soil against evaporation. The farmer cannot afford to 

 place layers of leaves over his fields, but he can afford to 

 make a mulch by using material that is already there. 

 He can make a mulch of the soil itself, provided the top 

 layer can be made loose and dry. How this is done will 

 be learned in the next chapter. 



EXERCISE. Repeat with several soils the " dripping test " given in 

 the second paragraph (p. 65). Which of these soils is least in need of 

 artificial drainage? 



NOTE TO THE TEACHER. If practicable, let pupils weigh cans of 

 two different soils, before adding 

 water and after dripping ceases. 

 How much water does each re- 

 tain? Emphasize the difference 

 in the water-holding power of the 

 two soils. If possible, compactly 

 fill two lamp chimneys, or bottles 

 with the bottoms off, with rather 

 dry soil, one a coarse sand, and 

 the other a clay (Fig. 46). Tie FJG ^*^ HOWING THE !^HT TO 

 cloth over one end of each to re- WH ICH MOISTURE RISES IN DIFFER- 

 tain the soil. Several hours be- EN T SOILS 



fore class time, set both in a basin Qn left> coarse . grained so il; on right, 

 in which the water is kept about fine-grained soil, 



an inch deep. Notice difference 



in height to which capillary moisture rises in each. Crosby's Exer- 

 cises 31, 33, 40, 41, will further impress these principles. 



