NOTES AND ABSTKACTS. 



565 



than pure water. Rich soils are less favourable to germination than 

 poorer. — F. J. G. 



Soil, The Effect of Partial Sterilization of, on the Production 

 of Plant Food. By Dr. E. J. Russell and Dr. H. B. Hutchinson (Jour. 

 Agr. Sci. iii. (1909) 2, pp. 113-144; 2 plates).— The hypotheses which 

 have been put forward to account for the increased yield following 

 partial sterilization of the soil are briefly reviewed and the authors' own 

 work fully detailed. 



It is found that there is a rapid increase in the amount of ammonia in 

 soils partially sterilized either by heat or by volatile antiseptics such as 

 toluene. This increase of ammonia is due to a slight extent, in the first 

 place, to the heating, but the subsequent rapid production to the growth of 

 micro-organisms. There is also an increase in the amount of the unstable 

 nitrogen compounds, but the humus appears to be little affected. There 

 is, if anything, a slight increase, rather than a decrease. 



The nitrifying organisms are destroyed below 95° 0., and by means of 

 treatment of the soil with toluene, and the soil is rendered unsuitable for 

 their growth. There is therefore no gain in the quantity of nitrates. 

 Neither does there appear to be any gain in the total amount of nitrogen, 

 but rather a small loss in the partially sterilized soil as compared with 

 the untreated soil. 



The authors conclude that the increase in ammonia is due not to the 

 removal of any ammonia-devouring agent, but to an increased production 

 of ammonia, for when small quantities of ammonia are added to the soil, 

 they are always recovered either as ammonia or nitrate. 



Bacteria increase very rapidly in the partially sterilized soil and at the 

 same time the ammonia greatly increases, the production of ammonia 

 thus appearing to be connected with the increase in numbers of micro- 

 organisms. Further, the increased production of ammonia appears to be 

 due rather to the increased numbers of germs than to any marked change 

 in the bacterial flora, and the conclusion is reached that there is in the 

 untreated soil a factor which limits the multiplication of bacteria, and 

 this factor is destroyed by partial sterilization ; this factor may be 

 reintroduced by the addition of untreated soil. Search revealed the 

 presence of large organisms such as infusoria, and amoebae and to these 

 is ascribed the role of limiting the increase in the number of bacteria in 

 untreated soil, (1) by actually devouring the bacteria, or (2) by competing 

 with them for food, and from their comparatively large size they must 

 prove very active competitors. 



Thus partially sterilized soils supply, not nitrates, but ammonia 

 and other nitrogen compounds to plants, and it must be assumed that the 

 plants are able to absorb and utilize these nitrogen compounds. 



The paper details the methods of experiment and the results obtained, 

 and must be consulted for these. — F. J. G. 



Solanum etuberosum. By C. T. Druery (Gard. Mag. No. 2908, 

 July 24, 1909, pp. 574). — The results of cultivation of this potato for the 

 last twenty years seem to prove that though in many ways very similar 

 to the common potato it is persistently resistant to disease. The seed 



