90 REPORT OF THE AGRICULTURAL RESEARCH 



certain biological processes necessary for fertility, to as- 

 certain approximately the organic manures most suitable 

 for application, with the important reservation that the 

 sample experimented on may not be truly representative of 

 the area to be treated; this source of error is greatly mini- 

 mised by the use of large samples and the introduction of 

 the method of using soil media in place of inoculating 

 liquid media with small samples of soil; thus in the old 

 method one gram of soil was generally used as inoculum 

 and the biologic activity of the soil as a whole was judged 

 therefrom, whereas in the method now used, estimations 

 of nitrifying and ammonifying capacity and efficiency, 

 and general biologic activity, are made with samples vary- 

 ing from 400 grams to 1,200 grams. 



III. — Special Enquiries. 



(1) Sewage Farms. — At the request of the Principal of 

 the Agricultural College, Nagpur, a series of investiga- 

 tions was commenced with a view to determining the effects 

 of the application of sewage upon the biological condition 

 of the soils of the College Farm. I visited Nagpur and 

 inspected the farm soils and the sewage installation, and 

 discussed with Mr. Allan and Mr. Plymen, the general 

 arrangement of the experimental plots to be put under 

 treatment. An arrangement was made for sending periodic 

 samples to Pusa for examination, and at the same time Mr. 

 Plymen agreed to carry out chemical analyses to determine 

 nitrate at Nagpur. 



(2) Rice. — An experiment was arranged to determine 

 the effect of soil toxins upon the growth of the rice plant; 

 this was in connection with the work of the Imperial 

 Mycologist upon the ' Ufra ' disease of this crop, 

 as it was considered possible that the incidence of this 

 disease might depend upon adverse soil conditions- Rice 

 was grown in pots in soil to which large quantities of mus- 

 tard cake were added, it having been found that the initial 

 stages of decomposition of this manure give rise to bodies 

 which are toxic to plants. The pots were arranged so that 



