15 



does not give as clear indications with pasture soils as it does with 

 arable soils. 



The rate of formation of ammonia and nitrates, which appeared 

 to he the determining factor, is under investigation in our laboratory. 



INVESTKiATIONS ON SICKNESS IN SOIL. 



This series of investigations deals with the remarkable falling 

 off in productiveness of soils kept well moistened, warmed, aerated 

 and supplied with organic matter, i.e., under conditions favourable to 

 the development of micro-organisms. It is difficult to account for 

 this result on the old view that the useful plant-food making bacteria 

 are the only active micro-organisms in the soil. On the other hand, 

 our new view that detrimental organisms are also present readily 

 explains the observed facts. Since the detrimental organisms are 

 more easily killed than the useful ones, it follows that partial steri- 

 lisation should be an effective method of dealing with such soils, and 

 experiments have fully borne out this conclusion. 



I. E. J. Russell and J. Golding. ''Sewage Sickness.'' 



Journ. Agric. Science, 1912. 5, 27 — 47. 



An extension of the experiments review^ed in the last Report. 

 It is shown that two factors come into play : a falling off in the rate 

 of percolation due to physical causes and a falling off in bacterial 

 activity due to an abnormal development of the detrimental factor. 



II. E. J. Russell and F. R. Petherbridge. ''Sickness 



in Glasshouse Soils.'' Journ. Agric. Science, 1912. 

 5, 86—111. 



The "sickness" that speedily supervenes in glass houses run at 

 a high pitch (such as cucumber houses) and less slowly in houses 

 run at a lower pitch (such as tomato houses) is traced to two causes : 

 an accumulation of various pests, and an abnormal development, 

 especially in cucumber houses, of the factor detrimental to bacteria. 

 The properties of this factor show that it is identical in character 

 with that present in normal soil and in sewage sick soil, and strongly 

 indicate its biological nature. No evidence of a soluble toxin could 

 be obtained. Partial sterilisation was found to be a satisfactory 

 method of treatment. 



III. E. J. Russell and F. R. Petherbridge. "Partial 



Sterilisation of Soil for Glasshouse Work." First 

 Report, Journal of the Board of Agriculture, 1912. 18. 

 Second Report {ibid), 1913. 19. 



These Reports are intended for practical growers and deal with 

 the application of partial sterilisation methods to sick soils. 



OTHER PUBLICATIONS. 



Besides the papers just described, the following have been 

 written by members of the Staff: — 



Winifred E. Brenchley. " Weeds, tlieir Peculiarities and 

 Distribution." Science Progress, 1912. 23. 



"Weeds in Relation to Soils." Journ. Board of Agric. 

 April, 1912. 



