374 
MESSRS. J. B. LAWES AND J. H. GILBERT ON THE RESULTS OF 
Table XXIII.—Estimated Nitrogen supplied in the Manure, recovered in the increase 
of the hay-crop, determined as residue in the soil, and not recovered in either in¬ 
crease or soil, to the depth of 27 inches. 
Nitrogen of manure. 
Per acre. 
Per cent. 
lbs. 
Supplied in farmyard manure in eight years. 
1606 
Recovered in increase in 20 years (over plot 3). 
291 
18T 
Not recovered in increase. 
1315 
81-9 
Residue, determined by soda lime, in soil 27 inches deep . 
911 
56-7 
Not recovered in increase or in soil. 
404 
25-2 
But even allowing due weight to the difficulties and uncertainties above referred to, 
and whichever basis of calculation be adopted, there can be little doubt—that only a 
comparatively small proportion of the nitrogen supplied in the farmyard manure was 
recovered in the increase of crop ; that there was a considerable accumulation of 
it within the soil; and that there was also a very considerable amount so far un¬ 
accounted for. 
Such a result would seem to require some confirmation. This is not wanting. Thus, 
among the series of field experiments at Bothamsted, wheat has been grown year after 
year on the same land from 1843-44 up to the present time, and barley in like manner 
from 1852 up to the present time. In the case of each crop, one plot has received 
14 tons of farmyard manure per acre per annum, and another a mixed mineral manure, 
without nitrogen, every year. The following Table (XXIV.) shows, for 20 years, the 
average annual amounts of nitrogen—estimated to be supplied in the farmyard manure, 
obtained in the produce by the mineral manure without nitrogen, in the produce by 
the farmyard manure, in the increase by the farmyard over the mineral manure, and 
the percentage recovered, and not recovered, in the increase. 
Table XXIV.—Nitrogen supplied in Farmyard Manure, recovered, and not recovered, 
in the increase of produce, of Wheat and of Barley. 
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. 
in increase. 
in increase. 
lbs 
lbs. 
lbs. 
lbs. 
Per cent. 
Per cent. 
Wheat, 20 years, 1852 71 . . 
200 7 
20-1 
493 
29-2 
14 6 
85-4 
Barley, 20 years, 1852-71 . . 
200 7 
23-9 
45'3 
2P4 
10-7 
89 3 
