SOIL AND FERTILIZERS 297 



are important constituents of good garden 

 soil, but neither is supplied with all the nutri- 

 tive substances demanded by plants for their 

 development. Both are light and porous and 

 are used to mix with stiffer soils to impart to 

 the latter the two qualities for which they are 

 most noteworthy. 



Soils, as they are found in yards, gardens 

 and fields, are mixtures. They partake of the 

 character of one or another of the types ac- 

 cording to which contributes most to the com- 

 position. A sandy soil, for instance, is that 

 in which sand predominates, while a stiff, 

 heavy soil, or clay soil, contains a greater 

 quantity of clay than a well-proportioned soil 

 should contain. These mixtures have in their 

 turn been named. First, there is loam, a soil 

 in which there is from 40 to 60 per cent, of 

 sand and the rest clay. This is the basis. If 

 a loam confains more sand — from 60 to 80 

 per cent. — ^it is known as a "sandy loam"; if 

 it contains less — 20 to 40 per cent. — it is 

 known as a " clay loam." In most instances, 

 some of the sand and clay is replaced by humus 

 and, if the quantity be large, the soil is desig- 

 nated as " black loam." 



Plant food is of three kinds — water, chem- 



