[ 522 ] 



dilute solutions of carbonate of potash, carbonate of soda 

 'and carborate of ammonia favour nitrification, but if the solu- 



2 *3 



tions are more concentrated than - - or ^ they check the 



1,000 1,000 



action of the ferment. If chloroform, CS 2 , or Phenol is passed 

 through soil, nitrification is arrested, owing to the death of the 

 organisms; continual drying of soils at iooC also prevents 

 nitrification. When urine of animals is allowed to ferment, in 

 considerable quantities, an undue proportion of ammonium 

 carbonate is evolved and nitrification is checked. The popular 

 belief that urine is injurious to land and that it burns up plants 

 is therefore correct, though diluted it is such a valuable 

 manure. In recommending the use of urine to cultivators the 

 necessary caution should be always given. The nitric fer- 

 ments find a fit soil in well-rotted manure which is not too 

 wet. More than three-fourths of the value of dung depends 

 upon the N. it contains. 



. 834. The quantity of saltpetre annually exported from 

 India is nearly 600,000 mnds. valued at over 40 lakhs of 

 rupees. Most of this goes to Great Britain and the U. S. A. 

 for the manufacture of gunpowder. It is more satisfactory to 

 use this manure in a comparatively pure form (say, of 5 to 6 

 per cent, refraction, which costs in Calcutta about Rs. 5-8 to 

 Rs. 6 per maund), than crude saltpetre which may contain 

 30 to 50 per cent, of foreign matter. 



835. Notwithstanding the potentiality of soils for accumu- 

 lating nitrates under specially favourable circumstances, the 

 application of manures to soils has for its chief object addition 

 of N. in an available form. In estimating the value of manu- 

 res in a practical manner, NH 3 , PaOs and K 2 O may be 

 valued at 6as., $as. and 2as. a Ib. respectively. NH 3 

 is valued in England even at Sd. a Ib. Indian soils being 

 particularly poor in N, and N being the most valuable plant- 

 food, the proportions of N in various substances that are or 

 can be used to enrich the spil, should be carefully studiecj. 



