INSTITUTE, PUSA, TOR 1917-18 123 



with the formation of C0 2 ; there is a positive 

 relation between the amounts of C0 2 thus 

 formed and the solubilization of phosphate 

 in the soil, but this varies with the character of 

 the latter. 



(2) Addition of soluble phosphate increased the 



ammonification rate in all the soils examined. 



(3) Addition of phosphate in many cases diminished 



the nitrification rate, apparently owing to the 

 disproportionate increase in non-nitrifying 

 organisms. The final result over long periods 

 of time in most cases showed no increase in the 

 total nitrate formed. 



IV. Indigo. 



The experimental factory referred to in the previous 

 annual report came into use at the beginning of the current 

 year (July 1917), and although its working was seriously 

 handicapped by the over-maturity of the plant, many valu- 

 able and interesting observations were made during the 

 short manufacturing season remaining. It is impossible 

 here to give any detailed account of the results obtained 

 which will form the subject of a full report shortly to be 

 issued as a memoir of the Department; the following 

 general summary will give some idea of the conclusions 

 arrived at and of the lines of further work made necessary 

 by the character of the results obtained. 



Inoculation with specific bacterial cultures. In the 

 previous year's report of this Section it was shown that 

 good reasons existed for believing that yield of indigo in 

 the process of manufacture depended in the first place upon 

 the completeness of bacterial hydrolysis of the indican con- 

 tent of the leaf; that this was determined by the presence 

 or absence of sufficient numbers of specific bacteria, and 

 that variations in yield between individual factories prob- 

 ably depended mainly upon the character of the bacterial 

 flora of the steeping vat, this being again determined by 

 that of the water supply. This contention was fully sup- 



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