THE SOIL I5 



well when the roots have reached deeper soil. This has fre- 

 quently been found to be the case in Ceylon and elsewhere. 



It is a fact, recognized by agriculturists for centuries, 

 that burning soil adds wonderfully to its fertility. Although 

 this method has been long practised, the reason why increased 

 fertility was assured was not understood. The reason is as 

 follows: The effect of high degrees of heat on the soil is to 

 destroy not only the greatest portion of the bacteria present 

 in the soil but also the whole of certain organisms, called 

 protozoa, which feed on these bacteria. The consequence of 

 the burning of the soil is that after a very short lapse of time 

 beneficial bacteria multiply without hindrance in the calcined 

 soil and its fertility is increased by the increased rate at which 

 nitrates are manufactured by these bacteria. 



What has been termed hot-weather ploughing has been 

 found in some districts of British India to be a means of attain- 

 ing the same results and one which is followed by a great in- 

 crease in the fertility of the soil. 



Where manures are not available, or are expensive, soil 

 burning would give a good start off to young plants. Where 

 plants are difficult to establish from sourness of soil this is an 

 effective remedy. Kilns are not expensive to build, and the 

 total outlay for burning the earth and transporting it would 

 only amount to a few cents per tree, an outlay which would be 

 amply repaid by the rapid growth of the trees and earlier arrival 

 at the tapping stage. 



Some chemists, WTiitney, Cameron and Schreiner among 

 them, have recently brought forward the theory that there is 

 an abundance of plant food in all soils; that all soils are com- 

 posed of practically the same decomposed rocks and are there- 

 fore almost identical in character; and that the soil solutions 

 are the same in all cases. Infertility, it is argued, is due to 

 other causes than lack of nutritive compounds, and arises from 

 the presence of poisonous organic compounds in the root 

 excretions of plants. 



This theory, although perhaps the net is cast too widely, 

 deserves serious examination. Every agriculturist is well 

 aware that certain plants, such as red clover, cannot have two 

 successive crops taken successfully from the same area. Clover- 

 sickness, arising from some poisonous matter supposed by 



