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in typical alluvial and regur soils the proportion of available 

 phosphates is usually over 'or per cent. Only in two cases he 

 found the proportion less than this. The soils of the Cawn- 

 pore,'Dumraon and Nagpur Experimental Farms contain -05 

 to "09 per cent, of total phosphoric acid, but soil from only one 

 plot in the case of ,the Nagpur and one plot in the case of 

 Dumraon farm showed the proportion of available phosphates 

 to be less than f oi per cent. About Jrd or Jth of the total 

 phosphates is usually in an available form in Indian soils, 

 while in English unmanured soils the proportion of avail- 

 able phosphates is about y^th, and in manured soils, higher, 

 about Jth. 



79. SOz. Like phosphoric acid when sulphuric acid is 

 present in a soil, it always exists in combination with some one 

 or other of the metallic oxides, with which it forms sulphates. 

 There is usually no simple means of determining with which 

 base it is associated, and for purposes of ready expression, 

 its amount is calculated in the form of the anhydride. The 

 majority of Indian soils contain remarkably little sulphate, 

 in no case as much as 'i per cent. An exception occurs in the 

 case of usar soils which are impregnated with sodium sul- 

 phate and sodium carbonate salts. 



80. COz. The determination of this is not of much con- 

 sequence. It usually exists in proportions not sufficient to 

 combine with the lime present and it may therefore be 

 assumed that the COs is present wholly or mainly in combina- 

 tion with lime. 



81. Organic matter and N . As a rule, Indian soils con- 

 tain little organic matter. The loss by heating is often due 

 chiefly to loss of combined water, and a knowledge of the loss 

 by combustion of a soil does not serve as a means of even 

 approximately determining the amount of that most valuable 

 constituent, hurnus. The loss by combustion occurs chiefly 

 where the proportions of iron and alumina are great. The 

 coffee soils of Sheveroys are rich in N and so are some soils 



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