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PRINCIPLES OF AGRICULTURAL CHEMISTRY 



If we assume that in the production of one gram of dry matter 

 500 grams water are transpired, we can calculate the concentration 

 of the absorbed water required to give the average composition of 

 various plants. This has been done and the results are in the 

 following table : 



If we compare this table with the preceding, we find that the 

 soil moisture does not contain enough phosphoric acid. In only 

 three of the soil series is even the maximum content of phos- 

 phoric acid sufficient for the requirements of any of the plants 

 (except sugar cane). The minimum content of the soil moisture 

 in potash falls below the concentration required, but the maximum 

 of all series of soils is above the maximum requirements of the 

 plants given above. 



Investigations were made by King 1 upon the water-soluble salts 

 of the soil, and the yield of corn and potatoes on eight types of 

 soil in North Carolina, Maryland, Pennsylvania, and Wisconsin. 

 He concludes that "there is a well-marked tendency for larger 

 amounts of water-soluble salts to be removed by the methods 

 adopted from the soils upon which the crops have made the 

 largest yields." The water-soluble material was estimated to the 

 depth of four feet. The addition of fertilizers was also found to 

 increase the water-soluble salts, and where determined under large 

 and under small plants in the same field, differences were also 

 1 Bulletin 26, Bureau of Soils. 



