236 THE FARMER OF TO-MORROW 



able to go even farther than this demand. 

 They are able to prove that plants actually at- 

 tain their best growth at these figures. 



Potash at 25 parts per million and phos- 

 phoric acid at 10 parts is not only a sufficient, 

 but an optimum concentration. The tables 

 (Bulletin 70, Bureau of Soils) on page 237 

 illustrate the point. 



In connection with these tables it should be 

 explained that the solutions used contained 

 soluble salts of the three elements in distilled 

 water nitrogen, potash and phosphoric acid. 

 Where only two of these salts were used it was 

 found in many cases that the plants attained 

 as great a growth as where the optimum quan- 

 tity of the missing element was added. This 

 would seem to nullify the results, except for 

 one interesting fact developed that plants 

 grown without any one of the three elements, 

 but with a sufficiency of the other two, de- 

 veloped peculiar pathological qualities that 

 would not be tolerated in actual farming con- 

 ditions. 



From the table showing results with potash 

 it would appear that the best results in grow- 

 ing seedlings was attained when the nutrient 

 solution contained between 24 and 32 parts of 

 potash to the million. 



