4i6 Biochemical Studies of Heated Solls [Mar. 



a high temperature are favorable to an immediate growth of green 

 plants. 



Bolley^ concludes that the destruction of the spores of disease- 

 prodiicing fungi and bacteria has more to do with the final increased 

 productiveness on heated soils than has either the destruction of 

 bacteria-loving protozoa, as claimed by Russell and Hutchinson, or 

 the increase of soluble matter found by Lyon and Bizzell. There 

 is undoubtedly considerable truth in this contention of Bolley, The 

 authors of the present paper feel that the whole question of the 

 effects of heating soils is a very complex one and one in which the 

 experimenter's Interpretation of results depends upon his training 

 and point of view; whether it be bacteriological, chemical or phyto- 

 pathological. It is very likely that the truth of the matter lies 

 somewhere on the border-lines of the three sciences indicated. 



PRACTICAL ASPECTS OF SOIL " STERILIZATION " 



For some time a f ew gardeners and Aorists have found that heat- 

 ing the soil for the benches of their greenhouses seems to produce 

 better plants, which were also free from the attacks of disease and 

 from competition with weeds. In India, also, the Hindu farmers 

 have long been in the habit of burning brush, cow-dung, etc., upon 

 the surface of the rice seed-beds. They call this process "rab" 

 and all speak highly of its efficacy in producing good crops. Mann'' 

 has discussed this practice and believes there are three main causes 

 for its beneficial results: (i), Favorable changes in the bacterial 

 flora of the soil; (2) organic nitrogenous matter is made more 

 soluble; (3) the physical properties of the soil seem to be improved. 

 Until within a few years the practice of heating soils in agricultural 

 work had but few advocates; but now through the influence of the 

 experiment stations and government bureaus it is being extended 

 and applied in many directions. 



Recently various bulletins and circulars have been published in 

 different states and countries, advocating the " sterilization " of 

 soils by heat, thereby f reeing the crops from fungus and insect pests 

 and also killing the seeds of weed plants. This treatment has been 



•Bolley: Interpretation of results in experiments upon cereal cropping 

 methods after soil sterilization. Science, 33: 229-34. 191 1. 



' Mann : Ann. Report of Dep't. of Agriculture, Bombay, pp. 50-4. 1908-9. 



