258 SOILS AND MANTJKES 



safety. It may be sown broadcast without much risk 

 of injuring the plants by contact with the leaves. It is 

 a very suitable form of nitrogenous manure for turnips 

 and potatoes. Owing to its relatively slow action it is, 

 perhaps, more suitable than nitrate of soda for these 

 crops, but not for mangolds. 



It is applied at the rate of from 1 to 2 cwts. per acre, 

 but the smaller quantity will generally be found sufficient 

 for ordinary purposes. 



Sulphate of ammonia, it has been said, may be safely 

 mixed with acid manures, such as superphosphate, dis- 

 solved bones, etc., but must not be mixed with lime, 

 manures, such as basic slag, which contain lime, or 

 alkaline substances like wood ashes, etc. It reacts with 

 these substances and gives off ammonia. 



Other Ammonium Salts. Chloride or muriate of 

 ammonia, NH 4 C1, has been used as manure, but not 

 often, because it costs more per unit of ammonia and is 

 no better than, if as good as, the sulphate. It is more 

 concentrated contains 31*78 per cent, of ammonia and 

 is more readily soluble in water. Chlorides have an in- 

 jurious effect on many crops, but the small quantity in 

 an ordinary dressing of the ammonium salt is not notice- 

 ably harmful. 



Other salts, such as ammonium nitrate, ammonium 

 phosphate, etc., though theoretically very desirable, are 

 never used as manures. The fertilising ingredients they 

 contain can be obtained more cheaply in other forms. 



Soot. Soot, the condensed smoke of coal fires, consists 

 mainly of carbon in a state of very fine division. It con- 

 tains, however, a certain amount of sulphate of ammonia, 

 and for manurial purposes may be regarded as a very 

 impure form of that substance. The proportion of 

 ammonia is naturally very variable, but usually amounts 

 to between 4 and 5 per cent., which is equal to about 



