IX.] ACTION OF LIME 261 



formed attacks the zeolites and replaces calcium by- 

 potassium, thus the potash is precipitated and lime 

 salts go into the drainage water ; when lime is applied 

 to the land the process is reversed and potash goes into 

 solution as bicarbonate. 



This may again be seen in the results quoted in 

 Table LXXX. of the application of lime to the 

 Rothamsted grass plots : on Plot 8, where potash 

 had not been used previous to the application of 

 the lime there is little or no increase of yield, because 

 there were no reserves of potash to be set free. That 

 lime acts in this fashion may also be inferred from 

 its beneficial effect upon clovers and other leguminous 

 plants in a mixed herbage, or by the remarkable 

 power of basic slag to promote the growth of white 

 clover in a pasture where it was formerly dormant 

 Other phosphatic manures have often little effect in 

 such cases, so that free lime in the basic slag, by- 

 liberating potash, is evidently as important a factor in 

 the growth of the clover as the phosphoric acid. If the 

 basic slag is applied to a soil poor in potash it has 

 little effect, and again after two or three applications 

 to grass land it ceases to show its previous beneficial 

 action upon the clover, because the readily attackable 

 potash in the soil has all been brought into solution 

 and a direct application of potash salts becomes 

 necessary. 



The fact that a solution of calcium bicarbonate will 

 react with the potash-containing double silicates in the 

 soil, so as to bring some of the potash into solution, is 

 only a particular case of a more general proposition, 

 which is applicable to any soluble salt brought into 

 contact with the zeolites. Whatever the salt may be, 

 if its base be one normally found in the zeolite, e.g., 

 either sodium, potassium, calcium, or magnesium, it will 



