Soil Organisms concerned in Nitrogen Cycle. 



521 



effect due to the natural acidity of the peat. The various soils were 

 incubated precisely as before, and at the end of 28 days it was found that 

 tbe nitrate-content of the soil containing bacterised peat had approached 

 very near to the maximum quantity shown in the previous experiment. 

 These two samples of soil were accordingly leached with distilled water, as 

 described above, to remove the accumulations of nitrate. The nitric nitrogen 

 which they contained was then estimated before they were re-incubated, and 

 the figures obtained are shown in the following Table : — 



Table VIII. 





Nitrate content (parts per million — mean of three determinations). 



Originally. 



After 

 7 days. 



21 days. 



28 days. 



35 days. 



47 days. 



54 days. 



1. 





70 



72 



86 



92 



105 



136 



156 



2. 





67 



68 



86 



95 



112 



140 



163 



3. 



Soil + raw peat 



66 



73 



77 



84 



79 



81 



59 



4. 



64 



76 



80 



89 



80 



80 



66 



5. 



Soil + carbonated peat 



61 



81 



98 



108 



136 



143 



173 



6. 



67 



84 



92 



99 



142 



167 



186 



7. 



Soil + bacterised peat 



59 



90 



356 



460 



94 



158 



195 











leached 



















= 37 









8. 



» >> >j 



60 



110 



380 



450 



101 



174 



213 













leached 



















= 62 









9. 



Soil + stable manure . . . 



65 



65 



71 



78 



89 



101 



128 



10. 



)> )> j) 



60 



64 



80 



85 



89 



109 



116 



It is evident from the results so far given that the addition of bacterised 

 peat to the soil results in an enormous accumulation of nitrate, which would 

 naturally be removed fairly rapidly by any growing crops. The figures in 

 the above Table also indicate that the introduction of the chemically 

 produced humate results in a slight increase in nitrate production, while the 

 addition of opening material in the form of raw peat and stable manure 

 tends rather to depreciate than increase the rate of nitrification in the soil. 

 The causes of this depreciation were not further investigated, since it had no 

 particular bearing upon the work. 



There is one other important factor which must be taken into considera- 

 tion in connection with the rapid nitrification in soils containing bacterised 

 peat. It is well known that this material contains a certain amount of 

 soluble nitrogen in the form of ammonium humate, and the question arises 

 as to whether this ammonia is merely being nitrified at a normal rate, or 

 whether any stimulation of the soil organisms is taking place in addition. 



