n6 SOIL CONDITIONS AND PLANT GROWTH 



Further investigations by Russell and Hutchinson (240) showed 

 that the most striking chemical changes that set in after partial sterilisa- 

 tion are the cessation of nitrification and an accumulation of ammonia 

 much in excess of the sum of the ammonia and nitrate in the untreated 

 soil. 



TABLE XLVIII. AMMONIA AND NITRATE ACCUMULATING IN A SOIL KEPT TWENTY- 

 THREE DAYS AT ABOUT 15 C. IN A MOIST CONDITION; PARTS PER MILLION OF 

 DRY SOIL. 



The accumulation of ammonia might be due either to an increased 

 production in the treated soils or to the removal by the treatment of 

 some agent, other than the nitrifying organisms, which is always con- 

 suming ammonia. The second supposition falls to the ground because, 

 when small quantities of ammonium salts are added to untreated soils, 

 the whole of the added nitrogen is recovered as ammonia and nitrate. 

 Hence it is concluded that the treatment had induced an increased 

 production of ammonia. 



Several considerations show that the production of ammonia sub- 

 sequent to the small initial gain on heating, or treating with toluene, is 



TABLE XLIX. NUMBERS OP BACTERIA AND AMOUNTS OF AMMONIA PRODUCTION IN 

 PARTIALLY STERILISED SOILS. 



After four days, nine days count lost by plates liquefying. 



