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The chemical and biological effects of the action of lime on soils 
are closely connected, since the biological effects are productive of 
changes in the chemical compounds present in the soil. 
These effects are general, to a greater or less extent, for all types 
of soil. 
1, Mechanical effects of lime on soils— The first of these has been 
sufficiently dealt with above in discussing the application 
of lime to peaty, clayey and light sandy soils. 
2. Chemical effects of lime on soils.- — Lime acts directly as a plant 
food, some plants requiring comparatively large quan- 
tities; — one of its principal functions appears to be to 
strengthen the woody portions of trees. 
The effect, however, of lime as a . direct plant food is of minor 
importance as compared with its indirect action on soils, due to its 
action as a base. 
It acts indirectly by. rendering available the dormant fertility of 
all soils. It liberates potash from the insoluble silicates with which 
it is combined. Quicklime or slaked lime is preferable to lime-stone 
for this purpose. It also assists the decomposition of organic nitro- 
genous matter, when not present in excessive quantity, and is thus 
especially beneficial in this respect on peaty soils. 
It corrects soil acidity which is generally harmful to vegetation. 
Many coarse grasses, sedges and other weeds which only flourish on 
acid soils disappear after the application of lime. 
It also renders phosphoric acid available by liberating it from 
its combination with iron and alumina with which phosphoric acid 
must be usually combined in the laterite soils in this country. 
It is also essential after the application of repeated dressings of 
other manures such as Ammonium sulphate, Kainit and Superphos- 
phates, the accumulated effects of which are to produce acidity. Thus 
in general the application of artificial manures necessitates a cor- 
responding increase in the application of lime. 
Biological effects of Lime: — The biological effects of lime on 
soils, as stated before, are intimately connected with the chemical 
effects. 
It is essential to the successful action of nitrifying bacteria, to 
combine with the nitric acid produced by these bacteria. It generally 
assists other fermentative actions in the soil, since those which 
are of benefit only occur in the presence of some base such as lime, 
whereas deleterious fermentation changes occur in sour soils in which 
nitrogen is actually liberated and escapes into the atmosphere. 
Another important function is its inimical action on a number of 
fungoid root diseases', the particular instance in connection with the 
cultivation of para rubber trees being its action on Fomes semitostus. 
