94 Practical Farming 



with the Ume in the soil and makes the sulphate of Ume 

 or plaster, and in this way is apt to cause an acidity in the 

 soil which is harmful to the prosperity of the microbes 

 that live with clover, and hence harmful to the growing of 

 clover. The notion that acid phosphate carries free sul- 

 phuric acid is generally erroneous, for a well-made phos- 

 phate has the acid completely neutrahzed. There is also 

 a notion which the manufacturers of bone fertilizers have 

 encouraged, that phosphoric acid from bones is better 

 than that from the rocks. Phosphoric acid is always one 

 and the same thing, no matter from what source it comes, 

 and the only difference is in its solubility. That in raw 

 bone is insoluble and also that in the pulverized rock. 

 From bone it will become available more quickly than 

 from pulverized rock, because the bone, if fine, decays 

 more readily, but the most readily available form is in 

 the dissolved rock or acid phosphate. 



Phosphorus, in the form of phosphoric acid, does not 

 leach from the soil as the nitrates will, but is held there 

 till called for by plants. 



Potash is the oxide of potassium, a metal- 

 f P t°"h^^^ ^^^ element, and as we have seen, one of the 

 essentials to plant growth. Formerly most 

 of the potash used was derived from the ashes of hard 

 woods, and these are still a valuable source not only of 

 potash but of lime, and to a more hmited extent of phos- 

 phoric acid. But the supply of ashes is totally insuiSicient 

 for the needs of modem agriculture, and the discovery of 

 potash salts in the salt mines of Germany was of the 

 greatest importance to the farmer. This potash is found 

 as a chloride in what is commonly called the muriate of 



