I .553 } 



phosphoric acid per acre within a depth of 9'', /. e. *oi per 

 cent, of PgOs soluble in a i per cent, solution of Citric acid 

 and most Indian soils have more than this. Total phosphoric 

 acid may be determined by the use of strong HC1 which dis- 

 solves the whole of lime and phosphoric acid though only a 

 portion (th to T V) f tne potash. A soil containing 700 

 or 800 Ibs. of available P 2 O 5 per acre within the first g" would 

 probably show 2,700 to 3,000 Ibs. of total P 2 O 5 .;; Of [the 700 

 Ibs. of available P2O 5 , a crop of 1,000. Ibs, of wheat or rice per 

 acre removes from the soil only 7 Ibs. of PsOs in either 

 case. The straw in each case removes another 3 Ibs. of 

 P2O 5 which is returned to the soil in one form or another. In 

 the case of paddy 3 Ibs. per acre go to the husk, 4 Ibs. to the. 

 rice and 3 Ibs. to the straw, the total quantity being the same 

 as in the case of wheat, though the outgoings if the husk and 

 the straw are returned to the soil are less in the case of 

 paddy. The gain of phosphoric acid by silt deposition add 

 irrigation is a good deal more than the outgoings and it is 

 only where no silt-deposit or irrigation takes ^placet -that the 

 question of recoupment of phosphoric acid in Indian -soils 

 need be considered. So far phosphatic manures have ;given 

 no decisive results in the experimental farms of : India, and 

 the value of manures should be principally judged;- frorn th$ ; 

 proportion of N they contain. Well-water used for irrjgar v 

 tion purposes is much richer both in phosphoric acid and N 

 than rain or canal water. Rain-water contains no phosphate 

 acid and only 4 parts of N in to million parts. Clear canal 

 water usually contains only 2 parts of N and 10. parts of P^Q^ 

 in 10 million parts and muddy canal -water, 4 parts of ; N:and 

 20 parts of PgOj in 10 million parts, while well-water, may 

 contain 150 parts of N and 100 parts of P^Os in 10 million, 

 parts. 



RRR 



