376 
MESSRS. J. B. LAWES AND J. H. GILBERT ON THE RESULTS OF 
Table XXV.—Nitrogen supplied in Farmyard Manure, recovered, and not recovered, 
in increased produce of Barley, during the years, and after the cessation, of the 
application. 
Nitrogen per acre per annum 
For 100 nitrogen in 
farmyard manure. 
Supplied in 
In produce 
In produce 
In increase 
farmyard 
by mineral 
by farmyard 
by farmyard 
Recovered 
Not recovered 
manure. 
manure. 
manure. 
manure. 
1 in increase. 
in increase. 
1 
Farmyard Manure every Year; 26 Years. 
lbs. 
Ibs. 
lbs. 
lbs. 
Per cent. 
Per cent. 
20 years, 1852-1871 . . . . 
200-7 
23-9 
45-3 
21-4 
10-7 
89-3 
6 years, 1872-1 877 . 
200 7 
15'5 
47-1 
31-6 
157 
84-3 
Total period, 26 years . . 
200-7 
22-0 
45-7 
23-7 
11-8 
88-2 
Farmyard Manure, 20 Years; 
Without Manure, 6 Years. 
20 years, 1852-1871 . . . . 
200-7 
23-9 
45-3 
21-4 
10 7 
89-3 
6 years, 1872-1877 .... 
15-5 
35-3 
19-8 
2-9 
Total period, 26 years . . 
22-0 
43-0 
21-0 
13 6 
86 4 
Thus, over the 20 years of the application (on the whole plot), 10'7 per cent, of the 
supplied nitrogen is so estimated to be recovered in the increase of crop ; over the next 
six years of the continued application, on half the plot, 15'7 per cent., and over the 
total period of 26 years ll'S per cent. On the other half, there was the 10 ‘7 per 
cent, of the 20 years’ supply recovered during the 20 years, 2'9 per cent, more of it 
during the next six years, and, in all, 13‘6 per cent, of the 20 years’ supply recovered 
in the 26 years. That is to say, of the 4014 lbs. of nitrogen estimated to he supplied 
in the 20 years, 86‘4 per cent., or 3468 lbs., remained unaccounted for in the increase 
of crop at the end of the 26 years. 
In reference to these results and conclusions, it is to be observed that the great 
reduction in the yield of nitrogen by the mineral manure in the later years is an 
indication of a gradual reduction of the more readily available nitrogen within the 
soil, and it is hardly to he supposed that, with the large supplies in the farmyard 
manure, the less readily available stores of the soil itself would be drawn upon to so 
great an extent as under the influence of the purely mineral manure. It is obvious 
that, so far as this was so, too much of the yield of nitrogen on the farmyard manure 
plot has been reckoned as derived from the soil, and too little as increase due to the 
manure—at any rate in the earlier years of the comparison ; and this observation 
would apply to the estimates relating to wheat as w T ell as to barley. 
We have not taken samples of the soils of the barley plots, and have not therefore 
the means of estimating how much of the unrecovered nitrogen of the manure still 
remains in the soil, possibly to be gradually yielded up to succeeding crops. But, 
supposing 89'3 per cent, remained unaccounted for at the end of the 20 years of the 
