H<>OS FIELD LEGUMINOUS AND WHEAT-FALLOW soils. 161 
It is, however, to be noted that this excess of nitrates on the clover 
plats docs not by an\* means indicate the whole extent of this greater 
nitrification, for Leguminous plants. Like cereals, absorb and utilize 
nitrates freely. I > 1 1 1 white clover, being l>nt a shallow rooting plant, 
can not directly utilize nitrates which have descended below the sur- 
face soil, and bo we And a great accumulation in the subsoil. It is 
for this reason that the white-clover plat s serve so well to show us 
evidence of the activity of nitrification going <>n in them. 
When we examine i he more heavily cropping and more deeply root- 
ing plants — vetches and Bokhara clover — we find in the subsoils far 
less nitrates. Probably more nitrates have actually been produced, 
but a smaller quantity has been Left unutilized. For instance, in L883, 
the vetch plats show (in feet l only about :54 pounds and 32 pounds 
of nitritic nitrogen per acre, as against 53 pounds in the white-clover 
plat: and in L885 the Bokhara clover shows only about 56 pounds 
per acre, as againsl nearly 69 pounds <>n the white-clover plat. 
Bui the most remarkably interesting plat is the Lucern plat. 
Lucern, as you are aware, is a very deeply rooting plant, sending 
down stout roots for many feet into the subsoil. So thoroughly has 
this crop Utilized the nitrates formed in the surface soil that we 
tind scarcely a pound of nitrogen per acre in any depth below the 
second, the total quantity of nitric nitrogen found to adepth of 9 feet 
being less than 17 pounds per acre, as against L02 pounds in the 
neighboring white-clover plat. 
It is now interesting to impure how far the accumulation of nitro- 
gen in these. soils under the influence of the leguminous vegetation 
can lie practically shown to influence their potential fertility for sub- 
sequent crops. Il has long been accepted thai a clover crop acts as a 
manurial dressing for the following wheat crop, and our modern 
methods of farming are being more and more attuned to the more 
# definite recent teachings of science on the value of the Leguminosae 
as reinforcers of soil nitrogen. It has been said that in 1898 three of 
the four series of these leguminous experimental plats were plowed 
up and put into wheat. Crops of wheat were taken in both L899 and 
1000. The following table shows the crops yielded on land that had 
been previously occupied by seven descriptions of leguminous crops 
in both years, and also the crops grown on the unmanured alternate 
wheat and fallow land of the same field, not only during the same 
seasons but in preceding years. The last-named results are stated in 
t wo ways, one giving the actual yield per acre of the bearing half of 
tin 1 land, the other the total yield per acre when the fallow half is 
also reckoned in the wheat area. The average yield of the unma- 
nured wheat plat in Broadbalk field is also given for comparison, and 
a summary of all the foregoing data is appended at the foot of the 
table. 
9385— No. 106—02 11 
