Phosphorus as a Soil Preserver 



When the University of Illinois thrashed its wheat on 

 an experiment field in McLean county, agricultural his- 

 tory was made. Upon the plots on which phosphorus 

 was one of the fertilizing ingredients the crop was more 

 than doubled, a record believed to be without precedent. 

 In the plots in which the phosphorus treatment bore a 

 part the average yield was more than fifty-eight and a 

 half bushels an acre, an average gain of thirty-four and 

 a half bushels an acre, which was mainly brought about 

 by phosphorus fertilizer. 



In these experiments the standard application of phos- 

 phorus in steamed bone meal has been at the rate of 

 twenty-five pounds an acre for each year in the rotation. 

 When raw rock phosphate is used about three times as 

 much is applied, which adds three times as much phos- 

 phorus to the soil but at about the same cost for the 

 bone. After two or three rotations the amount of rock 

 phosphate to be applied will be reduced to one-third of the 

 present applications. 



"The key to permanent agriculture is phosphorus," 

 said Dr. Hopkins. "To maintain or increase the amount 

 of phosphorus in the soil makes possible the growth of 

 clover and the consequent addition of nitrogen from the 

 inexhaustible supply in the air, and with the addition of 

 decaying organic matter in clover residues and in manure 

 made in large part from clover, hay and pasture and 

 from the larger crops of corn which the clover helps to 

 produce, comes the possibility of liberating from the im- 

 mense supply in the soil sufficient potassium, when sup- 



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