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NOTE. The student practices described in this laboratory manual are 

 the result of five years' experience by the authors in conducting classes in 

 a course of study in soil fertility. With some modifications the usual 

 chemical methods are employed, specific chemical directions being com- 

 monly based upon those adopted by the Association of Official Agricultural 

 Chemists. Otherwise these practices were originated in this University. 



The increasing number of students in this institution, and the fact that 

 some other institutions also desire to use our manual, induced us to put 

 it in printed form. 



Suggestions from other teachers of soil fertility regarding possible im- 

 provements in the manual will be gladly received. 



THE AUTHORS. 



College of Agriculture, University of Illinois, 

 Urbana, 111., July, 1905. 



