293 



In addition to the advantages of improved physical 

 texture in both cases, there is no doubt, in the light of 

 recent discoveries, that the well known effect of this 

 burning was partly due to the partial sterilization of the 

 soils which subsequently increased the bacterial flora. 



This no doubt occurs to a considerable extent v;hen 

 virgin jungle is felled and burnt in countries such as the 

 Federated Malay States, as, although probably in some 

 parts the beneficial and other bacteria are completely 

 killed by the high temperature on the surface, the tempera- 

 ture at a depth of say one foot would be only sufficient 

 to partially sterilize the soil and thus give rise to the 

 benefits of such a process. Clay soils are improved to a 

 remarkable extent by liming — the effect being principally 

 an improvement of the texture of the soil. 



The finer soil particles are coalesced by the addition oi 

 lime and lime salts and become flocculated into large 

 particles, so that such soils after treatment become more 

 open in textur^", retain less water, which is often a desi- 

 deratum in this country, particularly in flat lowlying lands. 



(A simple experiment nan be easily carried out to 

 demonstrate this flocculating efl'ect of lime on colloidal 

 clay particles. Two tall glass cylinders are taken and in a 

 separate vessel a mixture of clay and water is made. The 

 supernatant liquid from this mixture is then decanted into 

 the two cylinders — the liquid contains only the finest clay 

 particles which remain suspended in the water, for the most 

 part for an indefinite length of time. If a trace of lime, 

 slaked or quicklime or a solution of lime water be added to 

 one of the cylinders, the whole of the clay particles sus- 

 pended in the cylinder will quickly fall as a sediment to 

 the bottom of the liquid leaving a clear liquid above. 

 This experiment is simple and elementary but very 

 instructive). 



Clay soils after treatment with lime are more easily 

 cultivated and do not crack or cake when dry. 

 (c) Sandy Soils: — Although it may appear somewhat paradoxi- 

 cal, lime has also a beneficial action on light sandy soils, 

 rendering them more cohesive by cementing the loose 

 particles together. This is easily understood when we 

 consider the use of lime as a binding agent in the prepara- 

 tion of mortar. 



General Effects of Lime. 



The general effects of the application of lime can be conveniently 

 classified as follows : — 



1. Mechanical or Physical. 



2. Chemical. 



3. Biological. 



