Mar. 24. 1919 Ammonification of Manure in Soil 315 



I.— WHAT SOIL ORGANISMS TAKE PART IN THE AM- 

 MONIFICATION OF MANURE ? 



By J. W. Bright 

 INTRODUCTION 



The importance of the ammonification process in the soil has long 

 been recognized, although there has been a tendency on the part of 

 investigators to regard it as secondary in importance to nitrification in 

 soil fertility. Gainey (19), however, has recently claimed that the 

 fertility of a soil is limited by processes which precede nitrification — 

 namely, ammonification — rather than by nitrification itself. 



The present work has been undertaken for the purpose of determining 

 some of the organisms which actually cause the ammonification of 

 manure in soil under natural conditions; to ascertain the extent to which 

 they can carry on this ammonification; and to compare them with other 

 organisms known to possess the power of ammonifying laboratory media. 



A survey of the literature suggests that the active ammonifying organ- 

 isms in the soil are generally spore formers. This idea seems to be based 

 principally upon the conclusion reached by Marchal (j6) that the spore- 

 forming Bacillus mycoides is one of the most common of the soil organ- 

 isms and the one that attacks protein most energetically. It should 

 be noted, however, that he worked with a miscellaneous group of organ- 

 isms and of his eight most important ammonifiers only one, the non- 

 spore-former B. fluorescens liquefaciens , is a typical soil organism. J. G. 

 Lipman (jj) assumed that the spore formers were important ammonifiers, 

 as is evidenced by the fact that he referred to the B. suhtilis group and 

 the streptothrices as being the most prominent ammonifying organisms 

 numerically important in arable soils. Stephens and Withers {48) and 

 C. B. Lipman {32) also assumed this when they decided to use B. suhtilis 

 as the organism with which to do their experimental work on ammoni- 

 fication. 



That this idea is still held by some soil bacteriologists is shown by the 

 fact that in a recent investigation by Neller {39) (an associate of J. G. 

 Lipman), the spore-forming organisms B. suhtilis, B. vulgatus, B. my- 

 coides, and B. megatherium are used to represent "some of the more 

 common species of soil organisms" causing ammonification in the soil. 



While it is undoubtedly true that a great many spore-forming organ- 

 isms are capable of very active ammonification in manured soil, yet 

 there is good reason to doubt their activity under natural conditions. 

 Conn (6) has already pointed out that the spore formers probably exist 

 in the soil almost entirely as spores rather than as vegetative cells and 

 that their status as active ammonifiers in soil is doubtful. He further 

 shows {10) that the non-spore formers not only exist in the soil in great 

 numbers but that one group of them at least have proteolytic powers. 



