176 
INVESTIGATIONS ON ROTHAMSTED SOILS. 
In the superphosphate series it will be seen that the plats selected 
for examination were respectively the fallow and leguminous portions 
of the plats from which the roots are annually carted, while in the 
mixed-manure series the plats selected were the two corresponding' 
portions of the plat on which the roots are fed on the land. 
Whether we take the first three depths (1 to 27 inches), the fourth 
to the sixth depths (28 to 54 inches), or the first six depths together 
(1 to 54 inches), we find in each pair of plats that the leguminous por- 
tions contain more nitric nitrogen than the fallow portions. This is 
especially the case on the more fertile plat of the mixed-manure 
series. 
In the succeeding six depths the results are less regular, but the 
leguminous portion of the plat belonging to the more fertile series 
shows a greater quantity of nitric nitrogen than does the fallow por- 
tion. 
The nitric nitrogen, it will be seen, has been determined, through- 
out all the plats mentioned in the table, in the twelfth depth of 9 inches, 
or at a depth of nearly 9 feet from the surface. At this depth the 
nitric nitrogen is uniformly greater on the fallow portions than on the 
leguminous portions of the plats, and the consistency of these figures 
throughout suggests that the difference is an indication of a greater 
loss of nitrates from the fallow portions, owing to the fact that the 
land has been kept one year in four without vegetation. In our dis- 
cussion of the results obtained by examining the soils of Hoos field, 
we have seen how largely leguminous crops remove and assimilate the 
nitrates of the soil, as well as indirectly, by accumulation of nitroge- 
nous roof residue, augmenting their production. 
As the practical agricultural bearing of these famous rotat ion experi- 
ments in Agdell field was very fully brought before you by Sir Henry 
Gilbert, 1 I need not now direct further attention to them, my present 
object having been merely to place before you the aforesaid soil inves- 
tigations, which have so interesting a bearing in relation to the field 
results. 
1 U. S. Dept. Agr., Office of Experiment Stations Bui. 22. 
