252 



Soluble Humua and J'roductivotcus 



Table X. 



Experiments on the rate of nitrate production in the soil. These were 

 made with Untreated and Extracted Allotment Soils respectively, and 

 they involved periodical determinations of nitrate, ammonia, and 

 numbers of bacteria. Chalk was added to replace the carbonates 

 removed during extraction, and a third set was put up consisting of 

 extracted soil plus carbonate, seeded with 0-5 per cent, of untreated 

 soil to replace the bacterial flora that might have been de.stro3'ed by 

 the acid and alkaU treatment. Estimation.s were made at the start, 

 after one week, after three weeks, and after a considerable period. 

 The soils were stored in bottles, and the moisture content adjusted to 

 appraximately 16 per cent., this being known as favourable for bacterial 

 action. Table XI shows the changes that occur. 



It will be seen that the formation of nitrate is less marked in the 

 treated soils, and that ammonia tends to occur in (juantity and to 

 persist, whilst the untreated soil contains only the normal three or 

 four parts per million. Further, while the numbers of bacteria in the 

 untreated soil are iHirnial throughout- -about 20 millions per gram 

 downwards — the numbers in the extracted soils are initially very low, 

 then become abnormally high and remain above the usual level ; there 

 is however no corresponding increase in the production of ammonia 

 and nitrate. This is very similar to the result obtained by W. Buddin^ 

 on treating soils with non-volatile antiseptics. Sowing the extracted 

 soil with bacteria from untreated soil causes no marked difference in 

 the results. 



' Journal of AfjrHuHtiral Science, 1914. vi. ]i|i. 417—151. 



