98 THE PEOPLE'S FARM AND STOCK CYCLOPEDIA. 



loam, a sandy loam, or a sand. When humus predominates 

 largely it is called muck or bog soil. 



Sand. Perfectly pure quartz sand furnishes nothing for 

 the sustenance of the plant. Some sands contain valuable 

 mineral substances, which, in the laboratory of the soil, are grad- 

 ually fitted for the use of the plant. Any kind of sand, if 

 present in due proportion, is a valuable constituent in soil. It 

 causes the soil to grow warm readily in the spring; it favors 

 the escape of surplus water; it makes the soil porous, thus per- 

 mitting the roots of plants to permeate it readily in search of 

 food; it admits air to the soil, so essential for the chemical 

 changes; it makes the soil easy to work. Excess of sand is a 

 disadvantage. From its tendency to acquire heat, it may cause 

 the roots to perish in hot weather; it is liable to permit too 

 much of the water to escape in a dry season ; it is liable to 

 permit the water to pass through it so readily that the most 

 valuable fertilizing elements will be leached out. Soils that are 

 defective in this respect are called " leachy." Sandy soils usu- 

 ally respond very promptly to the application of fertilizers, but 

 the effect is usually short lived. Of all soils, sand has the least 

 power of retaining moisture and elements of fertility. 



Clay. The presence of this substance in large proportion 

 in a soil, renders it " retentive," by which is meant that it has 

 the power of retaining whatever is added to it, whether water or 

 manure. Clay soils are generally "strong " soils, and wear well. 

 They are less likely to be injured by bad treatment than other 

 soils, and are more readily restored, after having been " run 

 down." A soil containing excess of clay, however, is apt to be 

 heavy to work, difficult to drain, and " bakes " badly. 



Humus. The partially decayed vegetable matter to which 

 this name has been applied, is one of the most valuable con- 

 stituents of any soil. An artificial soil can be made which will 

 support plant life perfectly, and which contains no humus, but 

 practically all fertile soils contain humus, and the proportion of 

 this substance is sometimes the measure of their fertility. It 

 not only contains all the soil elements needed for plant life, 

 but it also contains carbon, or charcoal, in large proportion. 



