EXPERIMENTS OX THE MIXED HERBAGE OF PERMANENT MEADOW. 377 
application, and only 2'9 per cent, of the original supply were recovered in the first six 
years after the cessation of the application, or say 0‘5 per cent, per annum, it would 
obviously take from 170 to 180 years to recover the whole of it, if at the same rate 
as during the first six years. There can be little doubt, however, that part of the 
unrecovered amount has been lost by drainage, or otherwise ; and that whatever residue 
remains, a gradually decreasing proportion of it will be annually recovered. 
But samples of the soils of the experimental wheat plots have been taken, and the 
nitrogen determinable in them by the sodadime method estimated, at various times. 
The results so obtained enable us to form some judgment as to whether or not the 
whole of the nitrogen of the farmyard manure which is not recovered in the increase 
of crop remains available within the soil. 
In the autumn of 1865, after wheat had been grown 22 years in succession, samples 
of the soils were taken from many of the plots, in each case from the first nine, the 
second nine, and the third nine niches, of depth, or to a total depth of 27 inches. The 
results showed rather more than one-and-two-thirds as much nitrogen so determinable 
in the first nine inches of the farmyard-manured, as in the corresponding layer of the 
unmanured plot, and about one-and-a-half time as much as, to a corresponding depth, 
of any of the plots receiving artificial nitrogenous manures. The second and third 
nine inches also showed rather higher percentages than those of the unmanured, or 
of most of the artificially-manured plots. More recent determinations—that is, after 
the farmyard manure had been applied some years longer—showed more than twice 
as much nitrogen in the first nine inches as without manure. The following table 
gives the results for the two wheat plots, in the same form as at page 372 for the 
grass plots, founded on the determinations made on the samples of soil taken in 1865, 
after 22 years’ application of farmyard manure, and 22 wheat crops had been removed. 
The estimates of dry soil per acre are, for each depth, the average results obtained 
relating to eight samples from each of 11 plots. 
Table XXVI. —Experimental Wheat Field. Estimated amount of dry soil per acre 
at each depth; Nitrogen per cent, in the dry soils, and Estimated Nitrogen per 
acre, at each depth. 
Nitrogen. 
Average dry soil 
Per cent, in dry soil. 
Per acre. 
per acre, 
exclusive of 
stones. 
Plot 3. 
Unmanured. 
Plot 2. 
Farmyard- 
manured. 
Plot 3. 
Unmanured. 
Plot 2. 
Farmyard- 
manured. 
Manured 
+ or — 
Unmanui'ed. 
lbs. 
Per cent. 
Per cent. 
lbs. 
lbs. 
lbs. 
First depth, 1-9 inches . . 
2,287,155 
•1090 
•1882 
2493 
4304 
+ 1811 
Second depth, 10-18 inches . 
2,712,508 
•0738 
•0810 
2002 
2197 
+ 195 
Third depth, 19-27 inches 
2,848,973 
•0561 
•0619 
1598 
17 64 
+ 166 
Total, 27 inches . . . 
7,848,636 
6093 
8265 
+ 2172 
3 c 
MDCCCLXXX. 
