THE SOIL 13 



warmth, acted as a trap to hold the moisture. Now of course 

 a farmer cannot set a trap of planks over his fields, but he 

 can make a trap of dry earth, and that will do just as well. 

 When a crop like corn or cotton or potatoes is cultivated, 

 the fine, loose dirt stirred by the cultivating plow will make a 



FIG. 7. APPARATUS FOR TESTING RETENTION OF WATER BY 

 DIFFERENT SOILS 



mulch that serves to keep water in the soil in the same way 

 the plank kept moisture under it. The mulch helps to ab- 

 sorb the rains and prevents the water from running off the 

 surface. Frecjuent cultivation, then, is one of the best pos- 

 sible ways of saving moisture.^ Hence the farmer who most 

 frequently stirs his soil in the growing season, and espe- 

 cially in seasons of drought, reaps, other things being equal, 

 a more abundant harvest than if tillage were neglected. 



