QUESTION OF THE SOURCES OF THE NITROGEN OF VEGETATION. 
19 
salts and in the later as sodium nitrate, there is some, but comparatively little increase 
in the amount of nitrogen in the crop. 
In connection with the fact of the gradual decline in yield, it should he explained 
that owing to failure of the beans there was—in the second period one year of fallow, 
and one year of wheat; in the third period, one year of fallow; whilst in the fourth 
period, the first crop failed, and the land was left fallow during the second, third, and 
sixth seasons. The yields of nitrogen are, however, in each case, averaged for the 
period of 8 years. 
After the 32nd year, 1878, the land was left fallow for between four and five years. 
Under these circumstances, as will be seen presently, the stock of total nitrogen in the 
surface soil had become very low, direct determinations of the nitrogen as nitric acid 
showed that the already existing amount of nitric-nitrogen down to the depth of 
72 inches, was extremely small, whilst after several years of fallow there would be a 
minimum amount of crop-residue remaining for nitrification. 
On this land, exhausted for one leguminous crop, barley and clover were sown in 
the spring of 1883. The clover grew very luxuriantly from the first, much interfering 
with the growth of the barley. 
In our jraper in the ‘ Transactions of the Chemical Society,’ for June, 1885, we gave the 
amount of nitrogen as nitric acid found to the depth of 72 inches on the plot without 
manure, in that with the mineral manure alone, in that with the mineral and nitro¬ 
genous manure, and in that with farm-yard manure. We further estimated that the 
barley and clover crops would probably remove more than 200 lbs of nitrogen per acre. 
The amounts have, however, since been determined, and they are as follows :— 
Table VIII. — Nitrogen removed per acre in the barle}^ and clover crops. 
Previous condition of manuring’. 
1883. 
Barley and 
clover. 
1884. 
Clover. 
1885. 
Clover. 
Total. 
lbs. 
Ib.s. 
lbs. 
lbs 
Without maniTve . . . ' . 
45-0 
183-2 
52-7 
280-9 
Mineral manure and some nitrogen 
57-2 
193-1 
79-9 
330-2 
Mineral manure only. 
69'.3 
206-4 
81-6 
347-3 
It should be stated that the plots, the yield of nitrogen of which is here given, do 
not exactly correspond with those as given m the preceding Table, some of the crops 
being taken together where no difference in the produce was observable. Thus half 
the plot represented as without manure has been unmanured from the commencement, 
that is, for nearly 40 years, the other half having received small quantities of nitrogen 
to 1878 inclusive, but has since been entirely unmanured. Again, the results given 
in the second line relate to the produce on the plot with the purely mineral manure 
containing potash, given in Table VIL as No. 2, together with that of the plot No. 3 to 
D 2 
