THE BR0ADI3ALK WHEAT SOILS 
45 
sails have been withheld; and whether in consequence their root 
development lias been, in proportion to above-ground growth, less 
than in the ease of the plats less completely manured. Less annual 
root development would mean less root residue. Or, again, has the 
increased assimilative power conferred upon the plant by potash 
caused the above-ground growth to abstract from the roots, before 
maturity and death, more of the nitrogen taken Qp by the roots pre- 
paratory to utilization for the ultimate plant processes? On the other 
hand, we must not forget that we are for the moment speaking as 
though the first '.» inches comprised the whole of the soil ranged over 
by the roots. The roots of wheat go very deeply down into the sub- 
soil, and under different treatments the depth of root range no doubt 
varies, and the luxuriance of rootlet development in different layers 
of the subsoil probably also varies. And unfort unately t he irregulari- 
ties of the subsoil render it difficult to trace and compare quantita- 
tively the accumulations of organic nitrogen in the subsoil. Some of 
the subsoils Show accumulations in the direction in which we should 
expect to find them, while others do not. Or again, may it be that 
the denser and more vigorous growth of the wheat has allowed less 
grow th of weeds on the more richly yielding plats — weeds being, how- 
ever evil their habits, at least conservators of the nitrogen that they 
steal'.-' There is yet another view of the matter which is not new, but 
which should betaken into account, and which has been referred to 
In earlier communications from Kothamsted. It is that the accumu- 
lation of nitrogen under varying circumstances has its varying but 
necessary limitations — points of increase at which an equilibrium 
tends to establish itself. Such equilibrium is reached when the annual 
decomposition of root residue and the final resolution of its nitrogen 
into the form of nitrates, ami consequent annual drainage loss, equals 
the annual accumulation in root residues. It has, indeed, been pre- 
viously pointed out to you by Professor Warington that as these 
decompositions are the work of armies of living organisms, which 
must increase as their pabulum increases, the very accumulation of 
root residue furnishes an indirect means for its own increased destruc- 
tion. It is therefore possible that the somewhat decreased percentage 
of nitrogen on the most productive plats as compared with those of 
plats somewhat less productive may be due to some such reaction of 
natural agencies working toward the establishment of the final equi- 
librium which we must expect to be inevitably reached under any con- 
stant form of treatment. 
Perhaps, however, one is led to refine too much, ami it may be that 
the general harmony that otherwise prevails in this table of results 
lea<l> one to exaggerate the extent or significance of the, after all. 
Blight deviations of these plats from the rule to which, in a broad 
sense, they may still be said to conform, viz. that the greater the 
annual crop, and therefore the greater the quantity of nitrogen 
