QUESTION OF THE SOURCES OF THE NITROGEN OF VEGETATION. 
33 
extraction ; again showing that a certain proportion of tlie nitrogen of tlie soil is 
more easily attacked than the remainder. 
Ah the foregoing results illustrating the action of dilute organic acid solutions on 
the organic nitrogen of soils and subsoils were obtained in 1885, and 188G, by Mr. 
D. A. Louis, and the strengths adopted had reference to the degree of acidity of the 
sap of the lucerne roots collected in September, 1885, after the main gi'owth of the 
season was past. But finding the sap so much more strongly acid in April, 1887, 
that is at the commencement of the active growth of the season, it was decided to 
experiment with much stronger malic acid solutions. 
The following Table gives the results of experiments made by Dr. N. H. J. Miller ; 
in which the malic acid solution was of approximately 10 times the acidity of 
the September, 1885, root-sap, and the mixtures were made in the proportion of 
200 grams of the wheat-fallow subsoil to 1000 c.c. of the acid liquid. As before, a 
portion of the extract was removed after 1 hour’s contact, and the remainder after 
24 hours’. A second quantity of the acid solution was then added to the already 
once extracted subsoil, and portions were examined as usual after 1 hour’s and after 
24 hours’ contact. 
Table XII.—Showing the amount of the Nitrogen of subsoil dissolved by a malic 
acid solution of a degree of acidity much greater than that of lucerne root-sap. 
Nitrogen ditsolved per million soil. 
After 1 hour’s contact. 
After 24 hours’ contact. 
! 
T^M, j. £ 11 1-1 f First extraction , . 8*16 
VV lieat-tallow subsoil s ra i ^ j.* i t i 
oecoiici extraction . . . j ii*7i 
13-75 
7-03 
Even in the first extraction more than half the acid remained unneutralised, and a 
larger proportion still im the second extraction. Under these conditions of constant 
excess of acid, the raw subsoil gives up considerably more nitrogen, though there 
was, at the same, time, much more mineral matter taken up. In the first extraction 
the amounts of nitrogen taken up per million subsoil were 8’16 parts after 1 hour, 
and 13‘75 parts after 24 hours ; that is more after the longer contact. In the second 
extraction, however, less remained in solution after 24 hours’ than after 1 hour’s 
contact, from which it would appear that nitrogen once taken up had been deposited. 
Obviously the conditions of experiments in which an acid solution is agitated with 
a quantity of soil are not comparable with those of the action of living roots on the 
soil. The root action would necessarily affect only a very small proportion of the 
total soil. But the results recorded clearly show that the greater the acidity of the 
solution, the more nitrogen is taken up, and the question arises, whether the root 
MBCCCLXXXIX.—B. 
F 
