PHYSICAL COMPOSITION AND CLASSES OF SOILS 



93 



a soil and its physical analysis, is shown by the analyses of typical 

 Maryland subsoils published by Whitney. 1 



PHYSICAL ANALYSES OF MARYLAND SUBSOILS. 



The early market garden soil contains nearly 73 per cent. sand. 

 It has little power of retaining water and is therefore warm and 

 dry. It produces vegetables about ten days earlier than any other 

 soil in Maryland. 



The market garden soil contains more fine sand and more clay. 

 It is more productive but later in maturing spring crops than the 

 soil named above. It is superior to the first soil for peaches, 

 small fruit, and autumn crops. 



The tobacco soils contain 10 to 20 per cent, clay, the lighter 

 soil yielding a smaller crop but a better quality of leaf. The 

 wheat soils are somewhat heavier. The wheat soil (No. 4) is the 

 lightest soil upon which wheat can profitably be grown in Mary- 

 land. The soil is too light for permanent meadow or pasture 

 and too heavy for the best quality of tobacco. The wheat and 

 grass land is more productive than the wheat soil. The grass and 

 wheat soil is still more productive. 



Similar relations can be traced for other soils, between the 

 physical composition and crops adapted to them. Other factors 

 come into play, however, such as the location of the soil, its 

 depth, and its chemical composition. The physical properties of 

 a soil depend upon other things in addition to its physical com- 

 position, as we shall see. The relation between soil composition 

 and crop adaptation probably depends to a large extent upon 

 1 U. S. Weather Bureau, Bulletin No. 4. 



