4 6 



PARA RUBBER. 



MECHANICAL COMPOSITION. 



The Heneratgoda soils are light brown sandy loams in a 

 good mechanical condition, though the retentive power of mois- 

 ture is rather poor. The organic matter, although about normal 

 for the district, must also be considered poor. There is a fair 

 supply of nitrogen. The mineral plant food is generally poor, 

 there being only a small quantity of available potash and only a 

 trace of available phosphoric acid. The soils are both very sour. 



It is of very little practical value to the rubber planter to tell 

 him what mineral plant-food constituents are present in his soil ; 

 what it is necessary for him to know is the amount of plant foods 

 that is available in a soluble state. These foods must be in 

 such a condition as to be soluble in the sap of the root cells ; 

 this is only approximately equivalent to the amount of mineral 

 constituents which a i per cent, solution of citric acid is cap- 

 able of rendering soluble and not that rendered soluble by strong 

 mineral acids. 



The study of what may be termed the biological condition of 

 soil is of primary importance in modern scientific agriculture, and 

 it is one with which the up-to-date planter must sooner or later 

 be called upon to grapple. The amount of available plant food 

 in the soil is very largely influenced by the number of nitrifying 

 bacteria present. The nitrogenous compounds of organic 

 matter which are present in most soils are, under favourable con- 

 ditions, acted upon by bacteria which secrete a peptonising 

 ferment and change them into ammonia, and ultimately to 

 nitrates, in which condition they form a soluble plant food. The 

 essential requirements for the life and multiplication of soil 

 bacteria are air, moisture, and heat. Sour, water-logged land 



