Lime and Potash 291 



They are the seat of desirable bacterial changes which, 

 in their turn, like the hypothetical Philosopher's Stone 

 of the Middle Ages transmute the valueless into the 

 valuable. 



Lime as an indirect source of potash. — The beneficial 

 effect of lime on heavy soils is frequently ascribed to 

 its action as an indirect source of potash. The hme crowds 

 out the potash froni its insoluble combinations and ren- 

 ders it available. It must not be supposed, however, that 

 the formation of available potash in the soil is due en- 

 tirely to the action of lime on the potash minerals. Bac- 

 terial life plays an important part in that it furnishes 

 the carbon dioxid important in the weathering processes. 

 In the presence of carbonate of lime and of carbon dioxid, 

 the insoluble sihcate of potash is gradually converted 

 into carbonate of potash and also into other compounds 

 of the latter. It will be seen, therefore, that appHcations 

 of lime to the soil add to its available potash by direct 

 action on the insoluble potash minerals, as well as 

 by encouraging the growth of decay bacteria and the 

 production of larger quantities of carbon dioxid. 



Humus in relation to soil-potash. — In this relation, 

 humus plays fully as important a part as it does in the 

 case of phosphoric acid. Large quantities of readily 

 decomposable organic materials are essential in the 

 profitable utilization of the soil-potash. Indeed, the 

 influence of humus and of decay bacteria is, in some 

 respects, more important. From the standpoint of 

 insoluble potash locked up in the soil, it seems legitimate 

 for the farmer to employ every means at his command to 

 secure larger returns from it without much fear that 



