POTASSIUM SALTS 63 



Burnt lime is much more powerful in its action than 

 chalk or marl ; it should be used with discrimination, 

 lest the humus of the soil be unduly diminished. 

 Heavy clays, or soils rich in humus, are those most 

 benefited by burnt lime. In reclaiming peat bogs lime 

 is of the highest value. The acid humic matter of 

 the peat is neutralised by the lime, and the conditions 

 thus made suitable for the oxidation of the nitrogenous 

 organic matter and the production of ammonia and 

 nitrates. Lime prepared from magnesium limestone 

 (dolomite) is apparently of less value as a manure than 

 that made from normal limestone. 



The general effect of lime is to render available the 

 plant food already in the soil, without itself supplying 

 any significant amount ; liming cannot, therefore, be 

 successfully repeated except at considerable intervals. 



Potassium Salts. — These salts are obtained from 

 Stassfurt and Leopoldshall in large quantities; they 

 form a thick deposit overlying an enormous mass of 

 rock salt. The commonest potassium salt employed 

 as manure is kainite ; it is usually considered to 

 consist of sulphate of potassium, sulphate and chloride 

 of magnesium, and chloride of sodium. Kainite will 

 contain about 12' 5 per cent, of potash. Commercial 

 sulphate of potasskcm will contain 50— 52 per cent., the 

 commercial chloride (or muriate), 52 — 58 per cent, of 

 potash. 



Kainite, common salt, and other salts of potassium 

 and sodium are antiseptics, and consequently hinder 

 the decay of organic matter. They may be used to 

 prevent the decomposition of animal manure in the 

 stable or manure heap, but should not be sprinkled on 



