320 MAN'S USE AND CONSERVATION OF SOILS 



warm up quickly in the spring and dry out rapidly after 

 long wet spells. When humus and plant food in the form 

 of manure are added, these soils are especially adapted 

 for growing early crops and crops that do not require a 

 great deal of moisture, such as grapes. The " Fresno 

 Sand " of California and the sandy coast plains of the east- 

 ern United States are soils of this kind. 



LUMPY SOIL 

 The result of cultivating at the wrong time. 



In clay soil the particles are extremely small, as are also 

 the spaces between the particles. Water is therefore taken 

 up very slowly. It is, however, held tenaciously. Because 

 so much heat is absorbed in raising the temperature of the 

 soil water and in evaporating the water that slowly rises 

 to the surface, clay soils are cold. 



When clays become wet, they are very sticky and cannot 

 be worked. When they dry, they become very hard and 

 crack. If cultivated at the wrong time they break into 

 hard lumps and render further cultivation difficult. The 



