The Physical Character of Soils 35 



Classification similar appearance and texture vary greatly 

 of Soils -j^ |.j^g-j. chemical composition and produc- 



tivity. All through the upland country east of the 

 Blue Ridge Mountains there is found a clay loam of a 

 reddish color, which the soil survey made by the Depart- 

 ment of Agriculture has called Cecil clay, from the fact 

 that it was first noticed in the northern part of Cecil 

 County, Maryland. But it is well known that this Cecil 

 clay is of greatly varying character within limited areas, 

 being far more mellow and tractable in some places than in 

 others, and it varies also in fertiHty and productiveness. 

 Therefore a superficial soil survey, depending on the 

 similarity of appearance, is a poor guide to the character 

 of the soil. The productivity of a soil depends very 

 largely on the ease with which the plant food it contains 

 is dissolved in the soil water, and also on the coarseness or 

 fineness of the particles of which it is made up. A clay 

 soil containing a much larger actual amount of plant food 

 may still be less productive than a soil with much smaller 

 store of food, but which from its mechanical nature al- 

 lows the store to be more easily used by the roots of 

 plants. 



In the physical character of soils, the terms light and 

 heavy have reference to the ease or difficulty of culture 

 rather than to the actual weight; for, bulk for bulk, a 

 "light" sandy soil is really heavier than a "heavy" clay 

 soil. A soil will be termed sandy when 35 to 50 per cent, 

 of its material is made up of coarse grit. In a clay soil 

 the extremely fine particles are in the greatest proportion, 

 even making 95 per cent, in the heaviest clay. Between 

 the sandy soils and the clay are numerous gradations, dis- 



