NITROGENOUS ORGANIC MATTERS OF THE SOIL. 275 
great part, but a small proportion of it being in the form 
of ammonia-salts or nitrates, : 
Tn 1846, Krocker, in Liebig’s laboratory, first estimated 
the nitrogen in a number of soils and marls (Ann. Ch. u. 
Ph., 58, 387). Ten soils, which were of a clayey or loamy 
character, yielded from 0.11 to 0.14 per cent; three sands 
gave from 0.025 to 0.074 per cent; seven marls contained 
0.004 to 0.083 per cent. 
Numerous examinations have since been made by An- 
derson, Liebig, Ritthausen, Wolff, and others, with simi- 
lar results. 
In all but his latest writings, Liebig has regarded this 
nitrogen as available to vegetation, and in fact designated 
it as ammonia. Way, Wolff, and others, have made evi- 
dent that a large portion of it exists in organic combina- 
tion. Boussingault (Agronomie, T. I) has investigated 
the subject most fully, and has shown that in rich and 
highly manured soils nitrogen accumulates in considerable 
quantity, but exists for the most part in an insoluble and 
inert form. In the garden of Liebfrauenberg, which had 
been heavily manured for centuries, but 4°|, of the total 
nitrogen existed as ammonia-salts and nitrates. The soil 
itself contained— 
Total nitrogen, 0.261 per cent. : 
Ammonia, 0.0022 “ « 
Nitric acid, 0.00084 “ “ 
The subjoined Table includes the results of Boussin- 
gault’s examinations of a number of soils from France and 
South America, in which are given the quantities of am- 
monia, of nitric acid, expressed as nitrate of potash, and 
of nitrogen in organic combination. These quantities are 
stated both in per cent of the air-dry soil, and in lbs. av. 
per acre, taken to the depth of 17 inches. In another 
column is also given the ratio of nitrogen to carbon in the 
organic matters. (Agronomie, T I, pp. 14-21.) 
