510 Miss F. A. Mockeridge. Effects of ' Auximones on 



quantity of the normal material containing living organisms, the remaining 

 two portions serving as controls. A similar experiment was also arranged 

 with a clay soil. When three samples had been taken from each for 

 analysis of their nitrogen content, all the soils were placed in large glass 

 bottles loosely corked, so that they could be well shaken daily to ensure 

 aeration, and were placed on top of an incubator kept at 26° C, the 

 average temperature of the soils being about 20-22° C. The moisture 

 content was kept as uniform as possible, and after two weeks' incubation 

 the soils were again sampled, the total nitrogen being determined by the 

 Kjeldahl process. The results obtained were : — 



Table I. 



1. Soil alone 



2. „ „ 



3. Soil + sterilised 



bacterised peat 



4. >) n 



5. Soil + normal bac- 



terised peat 



Original nitrogen 

 content (mgrm. N per 

 100 grin. soil). 



Soil A, 

 Loam. 



Soil B, 

 Clay. 



Nitrogen content after 

 two weeks (mgrm. N 

 per 100 grm.soil). 



Soil A, 

 Loam. 



Soil B, 

 Clay. 



220 





295" 





224 



-224 



306 



,300 



227 





299 





229 





299 ~ 





224 



► 226 



302 



-299 



225 





296 





362 





465 





372 



■368 



462 



► 460 



371 j 





454 





375 ' 





464' 





368 



■ 370 



468 



► 465 



368 





462 





368 





458' 





360 



>364 



464 



► 462 



365 





465 





364 





466" 





371 



>369 



458 



>460 



372 





457 





236] 

 230 \ 235 

 238 J 

 237 1 

 241 I 239 

 240 I 

 410 



403 \ 404 

 400 J 

 398 | 

 405 U01 

 400 J 

 424] 

 430 U27 

 428 J 

 432] 

 428 \ 431 

 434 J 



313] 

 320 >318 



322 J 

 316 ] 



323 I 319 

 319 J 

 513] 

 509 U08 

 502 J 

 504] 

 514 U09 

 §10 J 

 527 ] 

 522 \ 524 

 524 J 

 526 



518 J- 520 

 517 



Gain in two weeks 

 (mgrm. N per 

 100 grm. soil). 



Soil A, 

 Loam. 



11 



13 

 36 

 31 

 63 

 62 



Soil B, 

 Clay. 



18 

 20 

 48 

 44 

 62 

 60 



The three analyses of each soil gave results which approximated very 

 closely to the mean, and therefore, in the following Tables of soil analyses, 

 only the mean of the three determinations will be given in each case, in 

 order to avoid unnecessary figures. The maximum deviation from the mean 

 for nitrogen fixation was +6. 



It is thus apparent that the addition of bacterised peat has increased 

 the activities of the nitrogen-fixing organisms already in the soil, quite apart 

 from any bacteria introduced. This result may have been due to (1) the 

 physical effect of the organic matter in improving the aeration of the soil, 

 and thus facilitating the activities of the aerobic bacteria ; (2) the effect of 



