522 Miss F. A. Mockeridge. Effects of Auximones on 



In order to put this to the test, an estimation was made of the soluble 

 nitrogen in bacterised peat, and a comparison was then made between the 

 rate of nitrification in soil containing one-tenth of its volume of this material 

 and in that containing an amount of ammonia equivalent to the soluble 

 nitrogen thus introduced, in the form of ammonium sulphate. Portions 

 consisting of 800 grin, of a fresh sample of Chelsea soil were used, and 

 one-tenth of the volume of this of bacterised peat weighed 32 grm., con- 

 taining 40 per cent, of moisture, the actual dry weight of the material 

 introduced into the soil being thus equal to 19 - 2 grm. This contained 

 l - 8 per cent, of soluble nitrogen as ammonia, so that the soluble ammonia 

 introduced was equivalent to l - 63 grm. ammonium sulphate, and this 

 addition was made to each of two portions of soil. All the soils were 

 incubated just as before, and the results obtained were : — 



Table IX. 





Nitrate content (parts per million — mean of three 

 determinations) . 



Originally. 



After 

 7 days. 



14 days. 



35 days. 



49 days. 



1. 



Soil alone 



25 



28 



42 



78 



104 



2. 



Soil + (NH 4 ) 2 S0 4 



27 



29 



40 



82 



110 



3. 



26 



45 



67 



195 



276 



4. 





25 



49 



75 



190 



259 



5. 



Soil + bacterised peat 



20 



54 



210 



480 



524 



6. 





22 



61 



201 



468 



541 



It is evident that the rate of nitrification in soil containing bacterised peat 

 is greater than that in soil containing an equivalent quantity of soluble 

 ammonia in the form considered most suitable for nitrification ; so that it 

 appears probable that, apart from supplying nitrifiable nitrogen, the addition 

 of bacterised peat increases the activities of the soil organisms. That there 

 is some factor in this material which has a beneficial effect upon nitrification 

 in soils, apart from any nitrogen it contains, is shown by the effect of the 

 phosphotungstic fraction upon nitrate formation. Attention has already 

 been drawn to this effect by Bottomley,* but fuller experiments have since 

 been made. To various uniform samples of the same soil were added the 

 phosphotungstic fraction obtained from amounts of bacterised peat equivalent 

 to (a) one-tenth the volume of soil, (b) one-fifth the volume of soil, (c) one- 

 sixteenth the volume of soil, and (d) one-eighth the volume of soil 

 * Bottomley, W. B., ' Boy. Soc. Proe.,' B, vol. 89, pp. 102-108 (1915). 



