THE NITRIC ACID OF THE SOIL. 269 
118) has proved that putrefying animal substances, as al. 
bumin, thus reduce nitric acid with formation of ammonia. 
For this reason, he adds, the liquor of dung heaps and 
putrid urine contains little or no nitrates. Boussingault 
(Agronomie, 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 in 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 is demanded for the culture of most 
crops these conditions cannot usually occur, as Grouven 
has taken the trouble to demonstrate (Zeitschrift fir 
_ 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 
soil 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 presence 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- 
