50 



MANURES 



Phosphatic Manures. 



Phosphorus is usually supplied as ashes, or in the form 

 of cake or fish manure, but it can be purchased in a more 

 concentrated form as bone meal, bone superphosphate, 

 steamed bones, rock superphosphate or basic slag (Thomas 

 phosphate). 

  Average analyses of these manures are given below : — 



The phosphoric acid in superphosphate is in a soluble 

 form and is therefore considered more valuable. For wet 

 lands, however, it is doubtful whether this is necessary, and 

 bone meal or fish manure are probably better. Steamed 

 bones are rich in phosphoric acid, but have lost a proportion 

 of their organic matter. Thomas phosphate contains a large 

 proportion of lime and is valuable in acid soils, but is heavy 

 and expensive to transport. It should be ground to a very 

 fine powder. 



Potash. 



Potash may be supplied as potassium sulphate, potassium 

 chloride (Muriate of potash), or Kainit. It is not generally 

 considered an important manure for South Indian soils, 

 though if analysis shows less than -25 per cent of total 

 potash in a soil, experiments should be tried with potash 

 manures. Kainit is a mixture of potash and magnesium 

 salts and contains often fairly large quantities of common 

 salt. Its use is practically unknown, most experiments with 

 potash having been carried out with the sulphate. 



