A^. 



JOMALOFAGRIQlTimiSEARCH 



Vol.. XVI Washington, D. C, January 13, 1919 No. 2 



NITRATES, NITRIFICATION, AND BACTERIAI. CONTENTS 

 OF FIVE TYPICAL ACID SOILS AS AFFECTED BY LIME, 

 FERTILIZER, CROPS, AND MOISTURE _ 



By H. A. NoYES, Research Associate in Horticultural Chemistry and Bacteriology, and ^^ ' -, 



S. D. Conner, Associate Chemist in Soils and Crops, Purdue University Agricul- ^^■TAt 



iural Experiment Station ''v 



INTRODUCTION 



The decay of organic matter and the transformation of nitrogen from 

 one chemical combination to another were known and studied long be- 

 fore bacteria were isolated. These phenomena were attributed to purely 

 chemical agencies until the discovery of the function of soil bacteria 

 proved them to be almost entirely due to microorganic life. Most in- 

 vestigations in soil bacteriology have dealt with either the products of 

 bacterial activities without reference to the number of organisms present 

 or with only an enumeration of the bacteria present in the soil. This 

 paper presents the results of an investigation taking into consideration 

 both nitrates and bacterial numbers, as well as a correlation of the two, 

 under certain specific conditions. 



HISTORICAL REVIEW 



NITRIFICATION 



The difficulties attendant upon keeping an adequate supply of avail- 

 able nitrogen in the soil are so great that those bacterial activities which 

 have to do w^ith nitrate formation are important and have been ex- 

 tensively studied. As early as 1660 Digby (2)^ mentioned the value of 

 nitrates in agriculture. He attributed the growth of plants to the "nu- 

 tritional and attractional " powers of a "nitrous salt." Many agricul- 

 tural writers of the early part of the nineteenth century followed the 

 lead of Liebig, who claimed that nitrogen was not needed as a soil amend- 

 ment. In 1856 Boussingault and Ville {8) independently published 

 experimental results which proved that nitrates are markedly beneficial 

 to plant growth, but it was not until 21 years later that Schloesing and 

 Miintz {22) demonstrated that nitrification in the soil was due to .organ- 

 ized ferments and does not take place in the absence of these ferments. 



1 Reference is made by number (italic) to "Literature cited, p. 41-42." 



Journal of Agricultural Research, Vol. XVI No. 1 



Washington, D. C. Jan. 13, 1919 



qx Key No. Ind.-s 



(27) 



