146 
INVESTIGATIONS ON ROTHAMSTED SOILS. 
a much more abundant yield, possibly owing to some extent to the 
solvent action of the sodium salt on the mineral constituents of the 
soil. In three out of the four plats of the nitrate sections we find 
more total nitrogen in the surface soil than in the corresponding plats 
of the ammonium-salts section. In the case of plat 4 of both A A and 
AAS (fully manured) the nitrogen is rather less than on plat A4, the 
soil having probably reached the stage in which nitrification had 
become more active than in the case of plat A4. 
Plat AA4 seems to have been richer than the corresponding 
ammonium-salts plat in 1868, but its nitrogen has since diminished, 
as in the case of the other section. 
The rape-cake plats (section C) are, as we should expect, all rich 
in nitrogen. Plats 3 and 4, which have given the best crops, are the 
richest. Much of the accumulation of nitrogen in this section must 
be attributed to actual accumulation of added nitrogenous matter 
and not to mere crop residue. Plat 4 gave lower results in 1882 than 
in 1868, a possible inference from whicii is that nitrification had 
become more active as the soil became richer. 
The farmyard-manure plats show a much larger accumulation of 
total nitrogen, the quantity, as we should expect, being considerably 
greater in the case of the continuously dunged plat than in the case 
of the plat on which the application of dung was stopped eleven 
years before, though this latter plat is still far richer in nitrogen than 
even the rape-cake plats. On the dunged plats the richness in 
nitrogen seems to appear also in the second depth; but the subsoils, 
like those of the Broadbalk field, are irregular. 
A table is here added showing the difference in nitrogen between 
the surface soils of the plats of the sections A, AA, AAS, and C, all 
nitrogenously manured, and those of the corresponding plats of sec- 
tion O, withoul nitrogenous manure. Plats 1, 2, 3, and 4 in every 
section receive, it will be remembered, the same minerals. The dif- 
ference between plats 1, or 2, or 3, or 4 of section O, and the corre- 
spondingly treated plat of any other section, is, therefore, to be 
referred solely to the direct or indirect treatment of the latter with 
nitrogenous fertilizers. 
