TUB NITKIO ACID OF TlIK SOIL. 2fi{i 



118) has proved that putrefying animal substances, as al- 

 bumhi, thus reduce nitric acid with formation of ammonia. 

 For this reason, he adds, tlie liquor of dung heaps and 

 putrid urine contains little or no nitrates. Boussingault 

 {A(/ro}iomie, II, 17) examined a remarkably rich alluvial 

 soil from the junction of the Amazon with the Rio Cupari, 

 made up of alternate layers of sand and partially decayed 

 leaves, containing 40" |„ of the latter. This natural leaf- 

 compost contained no trace of nitrates, but an exception- 

 ally high quantity of ammonia, viz., .05"]^. 



Kuhlmann [Ann. de Chim. et de Phys., 3 Ser., XX) 

 was the first to draw attention to the probability that ni- 

 tric acid may thus be deoxidized i:i the lower strata of 

 the soil, and his arguments, drawn from, facts observed 

 in the laboratory, appear to apply in cases where there 

 exist much organic matters and imperfect access of air. 

 In a soil so porous as i^ demanded for the culture of most 

 crops these conditions cannot usually occur, as Grouven 

 has taken the trouble to demonstrate [Zeitschnft fur 

 Deutsche Landwirthe, 1855^ p. 341). In rice swamps and 

 peat bogs, as well as in wet compost heaps, this reduction 

 must proceed to a considerable extent. 



In some, if not all cases, the addition of much lime or 

 other alkaline substance to a soil rich in organic matters 

 sets up rapid putrefactive decomposition, whereby nitrates 

 are at once reduced to ammonia (p. 266). 



In one and the same soil the conditions may exist at 

 different times that favor nitrification on the one hand, 

 and reduction of nitrates to ammonia on the other. A 

 surplus of moisture might so exclude air from a porous 

 Boil as to cause reduction to take place, to be succeeded 

 by rapid nitrification as the soil becomes more dry. 



It is possible that nitrates may undergo further chemi- 

 cal alteration in the i)resence of excess of organic matters. 

 That nitrites may often exist in the soil is evident from 

 what has been written with regard to the mutual convert- 



