64 
INVESTIGATIONS ON ROTHAMSTED SOILS. 
It happens, somewhat unfortunately, that the season preceding the 
taking of the samples in October, 1893, was far from being a normal 
season. The rainfall for the harvest year — September, 1892, to 
August, 1893, inclusive— was only 24 inches, as against an average] 
for the preceding seventeen years, of nearly 30 inches. The defi- 
ciency was chiefly in March, April, May, and June. During the 
whole of these four months less than 3 inches of rain fell, whereas 
there is normally from 8 to 9 inches during the same period As a 
con sequence, the crop of 1893, preceding the taking of t he samples, 
was a miserably small one, averaging all round only about 00 per 
cent of an average crop of grain and only 40 per cent of the average 
quantity of straw. From the point of view of analytical investiga- 
tion, however, it is to some extent a matter of regret that after har- 
vest and before the soil sampling in 1893, there was a somewhat heavy 
rainfall, viz, 11 inches, while a further fall of three-fourths of an inch 
took place during the period of sampling. Owing to this, much of 
the nitrogen that would in autumn be ordinarily found in the surface 
soil was no doubt washed downward into the second depth. The 
third depth, too, shows more than would probably be ordinarily 
found, and it will be seen that there is, as a rule, a very distinct 
break in continuity between the third and fourth depths. 
In regarding the results relating to the deeper la} T ersof the subsoil, 
it must be remembered that the field is artificially drained, and that 
it is at about the bottom of the third depth, or at 27 inches, that the 
soil water is tapped by the drainpipes whenever they run. Much of 
the rainfall must percolate downward into the lower subsoil with- 
out emerging from the drainpipes, which in a close soil like this, 
only run when rain is heavy or continuous. But the sudden decrease 
that we observe in many cases, in looking down the figures, in pass- 
ing from the third to the fourth depth, seems to be attributable in a 
great measure to the position of the drains, though it is also to be 
remembered that below the drains, we are also well below the depth 
at which the wheat roots collect the greater part of their food. Nitri- 
fication goes on mainly, though probably not exclusively, in the 
sin face soil, or in the upper depths of the subsoil. Such of the 
nil rates (or, for convenience, let us say such of the nitric nitrogen) 
as is not utilized by the growing wheat (which ceases to take up 
nitrogen actively some time before it is ready to cut) is gradually 
washed down. Some of this emerges in the pipe drainage should 
their he heavy rain, and what does not escape in this way must per- 
colate downward into the subsoil together with any such small quan- 
tity of nitric nitrogen ;is may be formed in the subsoil itself. 
In I lie absence of other evidence it might appear possible that the 
break observed between the third and fourth depths was due to 
relent ion by I he growing crop of t he nit rates present or formed in the 
upper depths during the growing season, which retention would 
