THK 11 IH 'AU15ALK WHEAT SOILS. 
05 
aturally limit the downward percolation into the subsoil prior to 
arvest, while the nitrates subsequently formed in the surface soil 
'ould hardly have had time to penetrate into the fourth depth. 
But the Kothamsted studies of nitrification, as you ma}' remember, 
a\ -e not been confined to the Uroadbalk field, but have been extended 
) the examination to an even greater depth of the subsoil of land 
ml does not happen to be pipe drained. Some of the results of 
liese studies are given in Sir Henry (rilbeit's Lectures, delivered in 
S'.W. 1 From those results it will be seen thai where there is no pipe 
rain age then* lias not been a break in the amount of nitric nitrogen 
bout or below the third depth of :» inches. This seems to support 
i«' conclusion that the sudden reduction shown in the Broad balk 
unples of I s«.»:5, between the third and fourth depths, is largely due 
) the tapping of the drainage water by the drainpipes. 
DOES NITRIFICATION OCCUR IN THE LOWBB SUBSOILS? 
Looking generally at the tables it will be seen that, as in the deep 
pries of plats previously examined, as described in sir Henry Gil- 
ert's Lectures, nitric nitrogen is found down to the lowest depth 
unpled. The question arises, how far is this due to percolation, or 
ow far is its presence due to the nitrification going on in the subsoil 
self? It has certainly been experimentally ascertained at Rotham- 
ed that the nitrogen of the subsoils is at any rate to some extent 
isceptible of nitrification if 1 he organisms are actually present and 
nder t he other condit ions of aerat ion ami temperature necessary for 
it ritical ion. It has even been proved that the nit rifying organisms 
o actually exist in the deep subsoils, though they seem to be very 
}w and very feeble as compared with those found in the upper 
epths, especially in the surface soil. But even if the actual condi- . 
ons naturally' existing in the subsoil allow of any appreciable nitrifi- 
ation in the lower depths, it would seem to be very feeble. 
If we take, for example, the case of plat 5, which receives no nitrog- 
noiis manure, and which is liberally supplied with mineral manures, 
> as to facilitate as fully as possible the utilization of the nitric 
itrogen produced by nitrification in the surface soil and upper sub- 
)il, we find that the nitric nitrogen existing below the drainpipes 
forages less than 1 pound per acre (actually 0.87 pound) in each 
epth of inches. Now in the unmanured wheat fallow soil of IIoos 
eld, sampled in July, 1883 (see Sir Henry Gilbert's lectures, p. 113), 
tie average quantity of nitric nitrogen was nearly 2i pounds per 
ere in each of the nine depths below the first 27 inches. In thai ease 
l U. S. Dept. Agr., Office of Experiment Stations Bui. 22, Tables 43 and 44, pp. 
13-115. Also paper "On some points in the composition of soils, with results 
lustrating the source of the fertility of Manitoba prairie soils." (Journal of the 
bemical Society of London, Transactions, 47 (1885), p. 380.) 
9386 — No. 106— 02 5 
