QUESTION OF THE SOURCES OP THE NITROGEN OF VEGETATION. 
9 
108 inches, corresponding to between 6 and 7 inches of rain, or to between 600 and 
700 tons of water per acre. 
After this summary of previously published results we may now turn to the con¬ 
sideration of new results of the same kind. 
2. NeuJ Determinations of Nity'ic Acid in Soils and Subsoils. 
The plots experimented npon are in the same series, with the same previous history, 
as those already referred to. Trifoliuin repens was ag’ain selected as the weak and 
superficially rooting plant; Melilotus leucantha was taken as a deeper and stronger 
rooting one; and Medicago sativa, or lucerne, as a still deeper and still stronger 
rooting plant. Samples of soil were taken at the end of July and the beginning of 
August, 1885, from 2 places on each plot, and in each case, as before, to 12 depths of 
9 inches each, equal to a total depth of 108 inches or 9 feet. 
Tlie following table (III.) shows the estimated yields of nitrogen per acre in the 
difierent crops during the experimental period from 1878 to 1885, the year of soil 
sampling, inclusive. The yields during the preliminary period have been already given 
in Table I. 
Table III.—Estimated yield of Nitrogen per acre, in lbs., in wheat alternated with 
fallow, and in various leguminous crops, without nitrogenous manure. 
U iimanured. 
Mineral manures only. 
Trljolium 
Melilotus 
Me<l kago 
7'epens. 
leucantha. 
sail va. 
lbs. 
lbs. 
lbs. 
lbs. 
1878 . 
29 
0 
53 
Not sown 
1879 . 
Fallow 
82 
130 
0 
1880 . 
24 
0 
36 
28 
1881. 
Fallow 
8 
60 
28 
1882 . 
18 
74 
145 
111 
1883 . 
Fallow 
0 
27 
143 
1884 ....>. 
29 
0 
56 
337 
1885 . 
Fallow 
97 
58 
233* 
Total, 8 years . 
100 
261 
565 
880 
Average annual . 
12 
33 
71 
(111') 
Thus, the wheat plot was again fallow when sampled; the total yield of nitrogen 
in the crops in the 8 years was only 100 lbs. per acre, and the average annual yield 
little more than ] 2 lbs. 
The Trifolium repens plots, after giving no crop in either 1883 or 1884, yielded 
produce containing nearly 100 lbs. of nitrogen in 1885, before the soil sampling; the 
total yield of nitrogen in the 8 years was 261 lbs., and the average annual yield 
33 lbs. 
* First and second crops only; a third crop, cut after the soil sampling, yielded 37 lbs. nitrog’en. 
MDCCCLXXXIX.—B. C 
