[ 560 ] 



rated and , ignited in platinum crucibles, and the potash and 

 the phosphoric acid in the residue determined in the ordinary 

 way. 



,915. From a series of experiments Dr. Dyer has conclud- 

 ed, that a soil containing less than *oi per cent, of available 

 phosphoric acid is in need of soluble phosphatic manures, and 

 a soil;containing less than '005 per cent, of potash is similarly 

 in need of soluble potash manures". 



916. It is not of much practical use determining the avail- 

 able nitrates present in the soil, as they vary from day to day 

 specially in the rainy season. It would be of greater import- 

 ance ,to -determine the nitrate-producing power of the soil, 

 but this is not a purely chemical question, but a chemico- 

 physico.-biplogical one, and analysis can be of little help in 

 such a question. Yet the determination of the total Nitrogen 

 by the combustion process is of great value as giving some 

 indication of the permanent value of the soil. It may be 

 assumed, however that all except virgin soils are benefited 

 by the application of soluble nitrogenous manures. 



The percentage of N,P2O 3 and K 2 O in different manures 

 can be. judged from the following table : 



>^ ,: N P 2 5 K 2 O 



(1) Ammonium Sul- 



phate ... 20% Nil Nil 



(2) Sodium Nitrate ... 15^,, Nil Nil 



(3) Potassium Nitrate 



(Crude) ... 2 to 13 Nil 7 to 40 % 



( 4 ) Street Sweeping^. g ; > }- 25 % 



-(5) Fresh Cattle dung 

 (ordinary cultiva- 

 ,. tors') ... -27 (Lime -28%) -18 -30,, 



(6) Well-fed cattle 



dung -35,, 14,, *i8- fl 



-(7) Rotten farm yard 



. . manure .... '9 . '17 n 



-(8):vCattle urine '56 '02 1-13 



