290 Bacter a in Relation to Country Life 



from rocks poor in potash are usually deficient in this 

 constituent. 



All soils contain their potash chiefly as silicate, an 

 inert substance insoluble in water. Because of its in- 

 solubility, it offers scarcely anything to the growing crops 

 in the absence of conditions favoring its decomposition. 

 Instances are not uncommon in which clay soils con- 

 taining 30,000 to 40,000 pounds of potash per acre to 

 a depth of one foot are markedly benefited by appli- 

 cations of 100 or 200 pounds of muriate of potash. This 

 may be readily understood from the fact that the in- 

 soluble silicate of potash is weathered very slowly under 

 ordinary soil conditions. 



Potash and the weathering process. — The weathering 

 process may be naturally so slow as to furnish available 

 potash enough only for a very meager harvest. The 

 farmer has it in his power, however, to hasten the weath- 

 ering process by the frequent stirring of the soil and by 

 the addition to it of large quantities of organic matter. 

 In either case, he unconsciously or.consciously encourages 

 the development of soil bacteria, the decay of humus, 

 the formation of carbon dioxid, and the decomposition 

 of the inert silicate of potash. As in the case of phos- 

 phoric acid, the carbon dioxid becomes the key that 

 helps to unlock the great stores of inert plant-food, — • 

 the key furnished by the busy hosts of bacteria working 

 in the dark recesses of the soil. 



What has been said of the insoluble soil-phosphates 

 ho.'ds good also in the case of the silicates of potash. 

 The soii-humus and the materials that go to make it, 

 attain a striking importance when viewed in this light. 



