CROPS AND SOIL IMPROVEMENT 



providing moisture, or ease of penetration of 

 plant-roots, or activity of bacteria, or other means 

 that will permit plants to remove what they need 

 for growth. Fertilizers supply fertility directly 

 and indirectly, but it is their direct service in meet- 

 ing a deficiency in plant-food that affords all 

 needed justification for their use by practical 

 farmers. 



Referring to the thirty years' soil fertility ex- 

 periments of the Pennsylvania station, Hunt 

 says that they " show that there is nothing inju- 

 rious about commercial fertilizers. For thirty 

 years certain plats in this experiment have re- 

 ceived no stable manures. No organic matter 

 has been added to the soil except that which was 

 furnished by the roots and stubble of plants grown. 

 These plats are not only as fertile as they were 

 thirty years ago, but they have yielded, and con- 

 tinue to yield, as good crops as adjacent plats 

 which have received yard manure every two years 

 in place of commercial fertilizer." 



Soil Analysis. There is wide misconception 

 regarding the value of chemical analysis of the 

 soil as an aid in making choice of a fertilizer. 

 Analysis has shown that some soil types are rela- 

 tively richer in plant-constituents than are others, 



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