FACTORS IN SOIL FERTILITY. 549 



other respects. In England we are obtaining the same sort of 

 results, with the greatly important addition of immunity to rust or 

 high resistance to rust included. The principles involved are sub- 

 jects on which Britishers in both countries may with advantage 

 interchange notes, but it is clearly useless to assume or think that 

 our experiences as regards varieties, or even as regards methods of 

 cultivation, can be of direct service, one to the other. Indeed, I 

 have in recent years, when actuated by the friendliest feelings of 

 sincere regard for Australian correspondents, advised them to try 

 our rejections rather than our successes, for it seems to me the 

 former may perhaps contain something valuable for Australian 

 environments, the latter most probably do not. The problem for 

 all wheat growers remains that we have to find or produce a variety 

 or varieties suitable for the many environments with which each of 

 us has to deal. The quest is long and troublesome, but well worth 

 the support of producers and consumers and of their Governments. 

 The consumer wants a plentiful supply of cheap bread, the pro- 

 ducer a good profit. A rise of price brought about by natural or 

 fiscal means may suit one class, it cannot the other ; whereas an 

 increase in yield resulting from the successful application of the 

 principle I have specified, will suit all, and it is well within the 

 bounds of possibility. 



4.— NEW FACTORS IN SOIL FERTILITY. 



By Dr. GREIG-SMITH, Macleay Bacteriologist to the Linnean Society of New South Wales. 

 (Published in extenso in Proc. Linn. Soc. N.S.W., XXXV., 808). 



[abstract] 



The fertilising effect that follows the treatment of soils with 

 volatile disinfectants, such as carbon bisulphide, ether, chloroform, 

 toluene and benzene and with heat, has been traced to the increased 

 growth of bacteria which ensues after the evaporation of the dis- 

 infectant. It is accepted that the increase in numbers corre- 

 sponds to an increase in the breaking down of the organic matter 

 of the soil, and consequent greater liberation of plant nutrients. 



It is known that the number of bacteria found in normal soils 

 is not the maximum possible ; there is a limiting condition. It 

 has been suggested that the limiting factor may be plant toxins, 

 bacteriotoxins, or phagocytic protozoa. The action of disin- 

 fectants and of heat upon protozoa can be understood, but the 

 behaviour towards toxins is not at all clear. 



The plant toxin idea is an old one, and although it may explain 

 the action of plant upon plant, it can have no bearing upon the 

 increase of bacteria after treatment with a disinfectant. The 

 bacteriotoxin hypothesis has been advanced by Whitney and 

 others in America, and the protozoal conception has been advanced 

 by Russell and Hutchinson. The latter arrived at the conclusion 



