QUESTION OF THE SOURCES OF THE NFTROOEN OF VEOETATION. 
51) 
Loss or gain of nitrogen. 
Peas. 
Clover. 
Without plant. 
per cent. 
per cent. 
per cent. 
Without manure. 
- 10-69 
- 5-10 
-b 0-26 
Kainite. 
- 15-32 
- 14-76 
Kainite and superphosphate •. 
0-00 
- 7-37 
Kainite, superphosphate, and calcium carbonate 
! 
- 12-72 
- 10-38 
- 10-24 
Thus, there was, in every case but one with the peas, and in every case with the 
clover, a loss, not a gain, of nitrogen. There was also a loss where the soil was 
maiiured, but left without a plant. 
On the other hand, in the experiment without either manure or plant, the figures 
show a gain of nitrogen. In reference to this last result, it should, however, be 
stated, that whilst in one German account it is, as in the Table, given as a gain of 
only 0'26 per cent, of the original nitrogen, in another German account, as well as in 
an English one, it is represented as a gain of 0’26 gram. In the first case the gain 
would be immaterial, whilst in the other it would be considerable, though still but 
small compared with the results obtained by M. Joulie. 
It is to be observed that whilst with almost exclusively non-leguminous growth, 
M. Joulie found gains of nitrogen in all cases, and in some very large gains. 
Dr. Dietzell, experimenting exclusively with leguminous plants, which are credited 
with being beyond all others atmospheric nitrogen accumulators, in all cases found 
losses instead of gains. How is this discrepancy to be explained ? It may be 
answered, that with a garden soil containing so much as 0'415 per cent, of nitrogen, 
it is not at all surprising that there should be some loss. Indeed loss would seem to 
be a perfectly natural result; and it is obvious that, neither from the combined 
nitrogen of the atmosphere, or that due to accidental sources, nor from free nitrogen, 
either directly or indirectly, did these reputed nitrogen-collectors gain nitrogen enough 
to compensate the losses from the rich soil. It is, indeed, recorded gains that require 
confirmation, with very careful methods of experimenting, before they can be accepted 
as conclusive evidence of the fixation of free nitrogen, and not as due merely to 
accidental sources of combined nitrogen, or to other experimental errors almost 
inevitable in experiments in which the soils and the plants are not enclosed, but 
exposed to the free air. 
In conclusion, all the results of Dr. Dietzell, excepting the one in which he found 
a gain, seem quite accordant with well established facts. On the other hand, if free 
nitrogen is really fixed in the soil under the influence of microbes, it certainly might 
be supposed that the result would be developed in a soil so rich in organic matter, 
and doubtless, therefore, in micro-organisms also, as a garden soil containing 0’415 per 
cent, of nitrogen ; and especially might it be supposed that it would be develo})ed in 
I 2 
