46 



now cultivating the flat bottom of the great Karoo lake, 

 and here and there they come upon these restricted deposits 

 of calcareous sinter, very convenient for either building or 

 mariurial purposes. It is a pity that similar stores of lime 

 do not exist all over the Colony. 



51. We have spoken of lime as a plant-food. No very 

 large quantity is required, but there must be some. Given 

 this small quantity, the remaining function of lime in the soil 

 is something quite different. It sets up a chemical action, 

 setting free in a soluble and available condition materials 

 which existed in the soil, for instance, potash and phos- 

 phoric acid, but in an insoluble form, incapable of absorp- 

 tion by plants. There is plenty of potash in soils derived 

 from a granitic base, but it is locked up in combination with 

 silica. A generous application of lime combines with the 

 silica and sets free the potash. The case is much the same 

 with insoluble phosphates. Then it has a remarkable effect 

 in assisting the nitrification of all organic manures added 

 in the usual way. Also upon soils of a more or less com- 

 pact clay its mechanical effect is very remarkable. It has 

 a peculiar power of altering that mechanical condition of 

 clay which makes it what is termed colloidal, that is, plastic 

 and impervious to water. This condition is, for cultivation, 

 about the most unpromising that there can be. It is 

 scarcely possible to do anything with such earth by ordinary 

 means. The only method is thoroughly to incorporate with 

 it heavy dressings of lime and establish reliable drainage 

 along the natural water-table. The result is that the clay 

 becomes, as it is termed, " flocculated," or collected into 

 little clots, around and between which moisture and air can 

 intervene. Thus, and thus only, can plastic clay be con- 

 verted into cultivable soil. 



52. Turning back to the analysis of fruit-ash, it will be 

 seen that the proportion of lime is considerable, amounting, 

 in the apple, to 63 per cent., in the orange to 22 per 

 cent, and in the plum to 10 per cent. Now all of this 

 large amount has to be given to the trees. It is therefore 

 a safe thing to be fairly liberal with lime top-dressings 

 to most orchards which have not a calcareous subsoil. 

 That is to say^ the only soils where lime freely used will 

 not be materially beneficial are those whose texture is 



