262 Fertilizers 



should be particularly rich in the mineral elements, phos- 

 phoric acid and potash. An application of 500 pounds 

 of a mixture containing 



Nitrogen 2% 



Available phosphoric acid 6% 



Potash 8% 



would provide an abundance of food, even should un- 

 favorable conditions intervene, but when grown on light, 

 unmanured soil without sod, a larger amount of nitrogen 

 should be used in connection with the minerals. An 

 application of 25 pounds of nitrogen, 35 of phosphoric 

 acid and 50 of potash is as small a fertilization as should 

 be recommended on soils of this character, since a yield 

 of 10 tons to the acre, containing 25 per cent of dry matter, 

 which is only a fair crop, would remove 60 pounds 

 of nitrogen, 25 of phosphoric acid and 70 of potash. 

 Hence, very large increases in yield could not be expected 

 from smaller dressings, unless conditions were absolutely 

 favorable throughout the entire period of growth. The 

 nitrogen, as in the case of field corn, may be derived from 

 organic sources, as the season of growth is the same, 

 the summer, which is the most favorable for encouraging 

 a rapid change of the organic nitrogen into the soluble 

 nitrates. The phosphoric acid should be in large part 

 derived from superphosphates, though since the season 

 of growth and the character of the crop and of its cultiva- 

 tion are conditions all of which favor a rapid change of 

 insoluble into available forms, a portion may be sup- 

 plied by ground bone or tankage. The potash may be 

 kainit or muriate, though if kainit is used, it should 

 be broadcasted and well worked into the soil before 

 planting. 



