17 



With this exception, it is generally true that bacterial multipli- 

 cation may go on without increasing the rate of production of 

 ammonia, but an increase in the rate of production of ammonia does 

 not take place without bacterial multiplication. 



The increase in bacterial numbers brought about by addition of 

 bacteria from the untreated soil into partially sterilised soil leads to 

 still further production of ammonia and nitrate, unless too large 

 a quantity of these substances is already present. But the sub- 

 sequent depression in bacterial numbers consequent on the develop- 

 ment of the detrimental organisms is generally (though not always) 

 without effect on the rate of decomposition, apparently because it 

 does not set in until too late. 



VI. "The Partial Sterilisation of the Soil by means of 



Caustic Lime" H. B. Hutchinson. Journal of 

 Agricultural Science, 1913. 5, 320—330. 



When a soil is treated with lime, either in the caustic or mild 

 form, an improvement of its physical condition results; the treatment 

 gives rise to a certain amount of chemical action with a liberation of 

 nutrient substances, and also, by neutralising any acids present, 

 provides a more favourable environment for the various classes of 

 organisms existing in the soil. 



This in itself is not sufficient to account for many of the results 

 that are obtained in practice. Caustic lime has a recognised value 

 as an antiseptic and, when applied to the soil, even in the presence 

 of large quantities of calcium carbonate, has a pronounced effect in 

 disturbing or even destroying the state of equilibrium, normally 

 existing between the micro-flora and the micro-fauna of the soil. 



The action of caustic lime has been found to be intermediate in 

 character between that exercised by volatile antiseptics and the 

 changes induced by high temperatures. In addition to killing many 

 bacteria and causing the death of the larger protozoa, which would 

 appear to exert a depressive action on the growth of bacteria, it 

 brings about a decomposition of the organic nitrogenous constituents 

 of the soil. It is highly probable that these decomposition products 

 serve as nutrients for bacteria and are subsequently resolved into 

 plant food. 



The depression of bacterial activities in soils treated with 

 caustic lime would appear to persist until all the oxide has been con- 

 verted into carbonate ; this is followed by a period of active bacterial 

 growth and increased production of plant food. The inhibitory 

 action of caustic lime on soil bacteria varies w r ith the soil and is 

 possibly governed by the organic matter present. 



In the main, pot experiments give results similiar to those ob- 

 tained in the Laboratory by bacteriological and chemical analyses. 



VII. "The Action of Antiseptics in increasing the Growth 

 of Crops in Soil. E. J. RUSSELL and WALTER 

 Buddin. Journal of the Society of Chemical Industry, 

 1913. 32. 



Chemical substances are now being put upon the market for 

 partial sterilisation of soils, and this paper is intended to afford 

 guidance to the works chemist, who is called upon to supervise the 

 preparation of such materials. Antiseptics may be used in practice 

 in the following cases : — 



V 



