54 PRODUCTIVE FARMING 



so closely as to make the access and circulation of air, heat, 

 and moisture difficult; the soil is, therefore, cold and heavy. 

 It is hard to work, and, unless well drained, crops are likely 

 to suffer both in wet and in dry seasons; in wet seasons 

 because the moisture and air do not pass through it readily 

 and the surplus water does not drain away, and in dry sea- 

 sons because the land becomes so hard as to prevent the 

 growth of roots, and the small amount of moisture in the 

 soil is not available to plants because it does not readily 

 circulate. 



Clay and Sandy Soil Compared. Clay soil is almost the 

 opposite of sandy soil, in many respects. Grains and larger 

 masses of sand do not stick together; if wet and moulded in 

 the hand, they will soon fall apart. Clay may be moulded 

 into any shape, and is sometimes used for making pottery 

 because the particles stick together when moist. Sand, 

 being open and porous, quickly loses moisture and plant- 

 food. Clay is so compact that it retains moisture and plant- 

 food. Sand admits heated air and soon becomes dry and 

 warm; clay admits air more slowly and remains wet and cold. 

 Because of these differences which make sandy soil easy to 

 work and clay soil hard to work, sandy soil is said to be light 

 and clay soil heavy, while in weight a quart cup full of sandy 

 soil is really heavier than the same amount of clay soil. 

 Both are valuable farm soils when supplied with enough 

 plant-food and vegetable mould, or humus. 



EXERCISE. To Show the Difference between Sand and 

 Clay. Use rather pure sand and pure clay. Make a wet 

 ball of each the size of a hen's egg. Place the two wet masses 

 on a board to dry. When dry, examine and note the dif- 

 ferences. . Which ball dried more quickly? Which is harder 

 to work when dry? 



EXERCISE. To Compare the Water-holding Power of 

 Sand, Clay, and Loam. In three boxes about the size of 

 cigar boxes place respectively some sand, clay, and black 



