510 SOILS: PROPERTIES AND MANAGEMENT 



nitrogenous fertilizers. A few such tests, in which nitrate 

 of soda and ammonium sulfate are used as a basis for com- 

 parison, are given in the table below, the statement being 

 in terms of percentage availability when nitrate of soda 

 is taken as one hundred. The experiments quoted were 

 conducted by Wagner and Dorsch, 1 by Johnson, Jenkins, 

 and Britton, 2 and by Voorhees and Lipman. 3 



Percentage Availability of Fertilizer Nitrogen 



One difficulty in drawing conclusions from these experi- 

 ments is that the substances grouped under the same 

 name are not always identical in the method of their 



1 Wagner, P., and Dorsch, F. Die Stickstoffdiingung der 

 Landw. Kulturpflanzen, Erstes Teil. Berlin. 1892. 



2 Johnson, S. W., Jenkins, E. H., and Britton, W. E. Experi- 

 ments on the Availability of Fertilizer-Nitrogen. Connecticut 

 Agr. Exp. Sta., 21st Annual Rept., Part 4, pp. 257-277. 1897. 



3 Voorhees, E. B., and Lipman, J. G. Investigations Rela- 

 tive to the Use of Nitrogenous Materials, 1898-1907. New 

 Jersey Agr. Exp. Sta., Bui. 221. 1909. 



