Soil Organisms concerned in Nitrogen Cycle. 511 



the soluble humate alone ; (3) the effect of the organic products, other than 

 soluble humate, formed during the bacterisation of the peat. If the first- 

 be the case, then a similar result might be expected upon the addition of 

 raw peat to the soil, if the soil be limed to correct the acidity of the peat ; 

 and, if the second be true, then chemically treated peat should produce a 

 like result. Accordingly, another six portions of soil from each of the same 

 localities were weighed out, two of each being mixed with one part in ten 

 by volume of raw peat and 1 per cent, of their weight of powdered calcium 

 carbonate. Two other portions of each were mixed with one part in ten by 

 volume of peat which had been treated with 2 per cent, of its weight of 

 sodium carbonate, and which was absolutely neutral, while the remaining 

 two portions served as controls. Since the soils already contained sufficient 

 lime, the chalk was added only to those containing raw peat. The soils were 

 sampled, as before, for their nitrogen content, and then placed on top of the 

 incubator at about 20° C. for a fortnight, at the end of which period they 

 were again analysed, with the following results : — 



Table II. 





Original nitrogen 

 content (mgrm. N 

 per 100 grin, soil — 

 mean of three 

 determinations). 



Nitrogen content after 



two weeks (mgrm. 

 per 100 grm. — mean 

 of three 

 determinations). 



Grain in two weeks 



(mgrm. N 

 per 100 grm. soil). 



Soil A, 

 Loam. 



Soil B, 

 Clay. 



Soil A, 

 Loam. 



Soil B, 

 Clay. 



Soil A, 

 Loam. 



Soil B, 

 Clay. 



i. 





220 



300 



230 



318 



10 



18 



2. 



Soil + raw peat ... 



221 



299 



232 



319 



11 



20 



o 



285 



369 



273 



381 



-12 



12 . 



4. 



290 



371 



270 



387 



-20 



16 



5. 



Soil + carbonated 



292 



365 



304 



382 



12 



17 





peat 















6. 





286 



368 



300 



388 



14 



20 



In these soils it is evident that neither the aeration nor the chemically 

 formed soluble humus are capable of producing an effect comparable with 

 that of the bacterised peat. The addition of raw peat appears to result in 

 one case in a loss of nitrogen, while the chemically treated peat does not 

 appreciably affect the nitrogen-fixing organisms. 



These and other results obtained from time to time all tend to show that 

 bacterised peat has the property of increasing nitrogen fixation in soils, 

 independently of the organisms which it contains, and quite apart from any 

 physical effect or any purely stimulating property of the soluble humates 



