

SOIL FERTILITY 

 LABORATORY MANUAL 



BY 



CYRIL G. HOPKINS, PH.D. 



PROFESSOR OF AGRONOMY IN THE UNIVERSITY OF ILLINOIS 



AND 



JAMES H. PETTIT, PH.D. 



ASSISTANT PROFESSOR OF SOIL FERTILITY IN THE UNIVERSITY OF ILLINOIS 



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GINN AND COMPANY 



BOSTON NEW YORK CHICAGO LONDON 



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