20 



BULLETIN OF 



Massachusetts Board of Agriculture. 



SOIL EXHAUSTION. 



By Gko. E. Stone, Ph.D., Pro/etsvr of Botany, ifassachutetts Agricultural College. 



The problem of soil exhaustion is one which the farmers of 

 Massachusetts have been brought face to face with for many years. 

 The land in this State having been deforested a number of times, 

 and having been under cultivation or utilized for agricultural 

 purposes for many generations, the primitive soil conditions, with 

 their original storehouse of available plant food, have been to a 

 large extent modified. The two factors that exert an influence on 

 the soil are its chemical composition and its physical properties. 

 These two factors are intimately connected, and, in general, one 

 cannot be modified without changing the other. The chemical com- 

 position of the soil is fully as important for plant growth as its 

 physical properties. The soil, however, may contain tons of plant 

 food which are not available. On the other hand, the physical 

 properties of the soil should be such that they are adapted to the 

 plant in order that normal root respiration can take place. 

 Unless the physical conditions are adapted to the plant require- 

 ments the amount and kind of available plant food exert very 

 little influence in the growth of plants. Many plants, however, 

 possess a wide range of adaptability and are not restricted to a 

 definite soil texture. In some cases it is also essential that the 

 particles of soil be of sufficient size, that their arrangements 

 should be of a certain order, so that air spaces of a definite size 

 are formed which are adapted to the particular plant under culti- 

 vation. It is, therefore, not only the size of the particles but their 

 arrangement which determine the physical properties of the soil. 

 The water-retaining capacity of the soil is also dependent upon 

 its physical properties. A light sandy soil from Cape Cod pos- 

 sesses a water-containing capacity equal to 35 per cent, while the 



