46 Alfred J. Ewart : 



exhausting action on the fertility nf the soil, especially in 

 regions with a high rainfall. 



Quicklime is often stated to ha"ve a special power of burning out 

 humus from the soil, especially if applied at the rate of one or 

 more tons per acre. This is quite incorrect as regards the 

 ordinary uiode of application of lime in Agriculture. Quick- 

 lime from the kilns, if directly put into the soil, would be rather 

 injurious thaai useful, since all lumps of any size would retain 

 their causticity in the soil long enough to delay seeding, and by 

 their local action would result in very patchy cultivation. In 

 ordinary practice, to secure fine subdivision and even distribu- 

 tion, lump lime must be allowed to slake in heaps on the sur- 

 face, which, when the lime has crumbled down, can be scattered 

 and harrowed in. Dui'ing this process the whole or the grearter 

 part of the lime is converted into carbonate of calcium by the 

 carbon dioxide of the air and soil. The presence of a carbonate 

 of an alkaline base or alkaline earth is one of the conditions 

 for the continuance of the nitrification of humus in the soil, 

 the nitrous and nitric acids produced displacing the carbon 

 dioxide from the carbonates in the soil. In this way the ac- 

 cumulation of acid, which is fatal to further nitrification, is 

 prevented, but it must be remembered that strong alkalies 

 like quicklime are very nearly as injurious to the nitrifying 

 ■and other soil bacteria as are free mineral acids. Hence we 

 should expect to find that the direct application of quicklime 

 would, for a time at least, result in a lessened bacterial oxida- 

 tion of the humus in the soil, as is in fact shown by the follow- 

 ing results, giving the percentages of humus by weight in the 

 dried soil of the various plots at three depths, at the beginning 

 and close of the exoeriments : — 



