THE BSOADBALK WHEAT Soil 
67 
charged drainage water that indubitably finds its way down to the 
chalk below. Some allowance, then, must be made for this in regard - 
big the 0.87 pound of nitric nitrogen pel acre found in each depth of 
the lower subsoil of plat 5, and such allowance, whatever it be, would 
rcduee to very small dimensions the nitric nitrogen that could be 
attributed to actual subsoil nitrification. 
Furthermore, if we turn to the results obtained from the drain 
gauges we fail to find practical evidence of any very appreciable sub- 
soil nitrificat ion. The structure of the Hot hamsted drain gauges is 
familiar to many of you. Each of these three gauges incloses an area 
of natural si>il with its natural subsoil, the area of each bring one 
one-thousand t hof an acre, and so const ructed t hat all t he rainfall which 
percolates through them can be collected for measurement ami analy- 
sis. In all three the soil is kept fallow, and they differ only in depth, 
containing respectively 20, 40, and '"><> inches of soil. Now, if nitri- 
fication went on appreciably in the subsoil, we should expect to find 
more nitric nitrogen in the drainage water from tin- deepest gauge 
than in that from the .shallowest As a matter of tact this is not the 
case. During the twenty years from 1*77-7* to ls:u;_n7 the nitric 
nitrogen yielded annually by the shallowest and the deepest gauges 
has been as follows : 
Taklk Rot In trusted drain gauges. 
Pounds. 
20-inch gange 35.07 
P>0-inch gauge 33. 87 
And, as is pointed out in the Rothamsted ' Memoranda" for the 
current year, the conditions of aeration are distinctly more favorable 
in the drain gauges than in the held. 
On the whole, then, we may consider that under natural field con- 
ditions the vast stores of subsoil nitrogen within the reach even of 
the deeply rooting wheat plant are, for all practical or economical 
purposes, unavailable for appreciable contribution to the nitrogenous 
sustenance of the crop. 
The conclusion is not new, but the subject appears to be one of suf- 
ficient magnitude to justify the space that I have been tempted to 
occupy in examining the latest contributions to the evidence that 
seems to bear upon it. 
NITRIC NITROGEN IX THE UNMANURED AND THE DUNGED PLATS 
AND THE RAPE-CAKE PLAT. 
When we come to a detailed consideration of the results we are, as 
in the consideration of the total nitrogen contents, naturally led to 
compare first the persistently unmanured plats 3 and 4 with the two 
dunged plats, 2a and 2b. Here we much regret the absence of deeper 
samples. As it is, we must be content in the case of these, as in the 
