72 -R. GREIG-SMITH. 



to soil. The farmer rarely puts raw manure into the soil, 

 and if green manuring is employed, time is given for it to 

 ferment before the crop begins to grow. What holds for 

 complex manures, also holds for simple carbohydrates such 

 as starch. Unless time is given for this to decay, the crop 

 is injured. The injurious effect of adding sugar to soil has 

 been noted by several investigators, 1 by some of whom it 

 is ascribed to the loss of combined nitrogen by denitrifica- 

 tion, although Lipman 2 has shown that the addition of 

 glucose, or other organic matter, depresses the crop even in 

 the presence of an excess of fertilising material containing 

 nitrate. Indeed nitrates were found in the tissues of the 

 impoverished plants. Some reason other than denitriflca- 

 tion must therefore be found to account for the crop 

 depression. 



The addition of an excess of bulky fertiliser, such as 

 farmyard manure, has been found to diminish the crop 

 and at the same time to lessen the bacterial counts. 3 The 

 reason for this is obscure, although some light is thrown 

 upon the .matter by the work of Temple, 4 who showed that 

 the sterilisation of raw manure increases the bacteria in 

 the soil, as well as the general fermentable activity. The 

 work points to the destruction by heat of depressing sub- 

 stances or toxins in the raw manure. 



From what has been done, the inference appears to be 

 that, easily fermentable organic matter in the soil gives 

 rise to an undesirable fermentation, with the production of 

 depressing or toxic substances, and time must be allowed 

 for these to decay or the crop will suffer. 



Bacteria, 'while growing in soil bring about the decay of 

 the organic matter, and in doing so cause the liberation 



1 Munter and Eobson, Cent. Bakt. 2 te, 39, 419. 



2 N. J. Ag. Expt. Stn. Eept. 257. 



3 Brown, Cent. Bakt. 2 te, 39, 523. 

 * Ibid., 34, 204. 



