60 
INVESTIGATIONS ON ROTHAMSTED SOILS. 
It will be seen that, even at these great depths, far removed from 
surface influences, we find much the same proportion of nitrogen (viz, 
about 0.04 per cent) as in the Rothamsted deeper emy subsoils, though 
we find, it is true, more carbon and higher carbon to nitrogen ratios 
than in the Rothamsted subsoils. 
The general inference would seem to be that in these ancient 
deposits, whether mere clay or calcareous formations differing much 
in their general characters, there is a small but fairly constant per- 
centage of nitrogen, viz, about 0.04 per cent, due presumably to the 
last surviving organic residue of the multitude of animal and vege- 
table remains accumulated in their suboceanic period. This small 
percentage of nitrogen, which seems to remain unaltered at a depth of 
1,000 feet, seems to be equally unaltered within a few feet of the sur- 
face, despite thousands of years of surface vegetation, the influence 
of which on the permanent organic nitrogen contents of the subsoil 
seems to be scarcely appreciable below about 4 feet from the surface. 
Small as it seems in percentage, the quantity of soil and subsoil 
nitrogen is enormous. In what precise organic form it exists we do 
not know, but it seems, except near the surface, to be protected, prob- 
ably by conditions of temperature and aeration, from the microbic 
influences which promote the decompositions culminating in nit rifica- 
tion. Indeed, for aught that we know, some part of this clay nitro- 
gen may be in a condition in which it is not even susceptible to such 
influences. Even in the surface soil, where nitrogen is steadily nitri- 
fied (and lost, unless the cropping conditions are favorable to its 
! cassimilation), the nitrates are probably mainly yielded by the old 
crop residues rather than by this original clay nitrogen. In the Broad- 
balk field, plat 5 — the plat persistently manured with full minerals, 
but starved for want of nitrogen (see Table 14) — is poorer than its 
ammonia-fed neighbors in the first 27 inches, but below this it hap- 
pens to be a good deal richer in total nitrogen than the prosperous 
adjoining plats. Its crops are starving for want of nitrogen in an 
assimilable form, and yet it contains in the first three depths (27 inches) 
6,401 poii nds of nitrogen; in the first 6 feet, 14,056 pounds; and in the 
first 7{ feel no less than 17,470 pounds of nitrogen per acre. Yet we 
know from experience that a small top-dressing of sodium nitrate or of 
ammonium sails would in a single season convert its poor annual yield 
of 1 1 1 bushels of grain, wit h HH hundredweight of stunted straw per 
acre, into a rich crop of probably )$f> bushels of grain per acre, with a 
luxuriant growth of straw. 
Nature is niggardly, then, in her annual dole from this great store. 
Whal docs she spare us, and how? 
We have among the Rothamsted records sufficient data relating to 
land unmanured with nitrogen to enable us to answer this question, 
bul before passing on to it we may properly stop to consider the 
results indicating the ^nitric" nitrogen, or nitrogen existing as 
nitrates, in the different soils and subsoils. 
