106 SCIENTIFIC REPORTS OF THE AGRICULTURAL RESEARCH 



nitrogen; this substance has a decided retarding effect upon 

 nitrification. Acidification of the filtrate from the above 

 yielded a white crystalline substance soluble in dilute acids 

 and containing rather more than 4 per cent, of nitrogen: 

 this substance was found to increase the rate of nitrification 

 in Omelianski solution. 



Phosphate requirements of soil bacteria and their 

 relation to plant growth. A series of experiments deal- 

 ing with this subject was initiated; the results so far 

 obtained do not suggest that solubilization of tricalcic soil 

 phosphates by bacterial action is sufficient in amount to pro- 

 duce a surplus supply of soluble phosphate for the direct use 

 of higher plants, but rather that the bacteria dissolve only 

 sufficient for their own requirements. It seems clear, how- 

 ever, that such important fertilizing bacterial actions as 

 nitrification depend for their occurrence in any useful 

 degree upon proper supplies of phosphatic bacterial food, 

 and it is also clear that carbonic acid resulting from bac- 

 terial action in the soil will in course of time solubilize 

 sensible quantities of mineral phosphate. 



Biological analysis of soils. Numerous samples of soil 

 were analysed by the method elaborated in this laboratory , 

 much useful information has been obtained in this way as to 

 the close relation between bacterial activity and soil fer- 

 tility. Application of the method to reh soils in the Pun- 

 jab was found of great value by the Agricultural Chemist 

 to the Government of the Punjab, whose assistant had been 

 trained in its use in this laboratory. It is to be hoped that 

 the untimely death of Mr. Barnes, whose criticism and 

 advice in connection with the chemical methods involved 

 were of great value to me, will not prevent a continuation 

 of this enquiry. 



Familiarization with the use of the method forms a use- 

 ful preliminary training for students in this Section. 



G-reen-manuring. Field experiments on the modified 

 method of green-manuring devised in this laboratory, have 

 been continued in collaboration with the Imperial Agricul- 

 turist on the farm, and also in the bacteriological area. 



