Field Experiments on Potatoes. 
395 
IV. — Showing the Increase in Potatoes on each Plot, calculated to the 
Acre, and Average of Increase. 
J'lots 
Makuee. 
Mineral Superphosphate . . 
Dung 
[Mineral Superphosphate .. 
and 
Crude Potash-salts 
Crude Potash-salts 
Common Salt 
' Mineral Superphosphate .. 
and 
Common Salt 
Dung 
Average produce of Unmanuredl 
Plots / 
Increase. 
Increase 
per Cent, (in 
eacli Plot. 
Tons. cwts. qrs. 
0 8 0 
3 13 3 
16 
4 
0 
lbs. 
n 
25' 
0 
(Decrease) 
10 2 11^ 
17 3 194 
20 
187 
91 
12 
247 
1 19 
It will be seen that the unmanured plots on an average pro- 
duced barely 2 tons in round numbers, showing that the land 
was in a poor condition. On this account it was well adapted 
for manuring experiments ; and it is, therefore, greatly to be 
regretted that the dry season of 1867 interfered, in a measure, 
with the characteristic effects which the various fertilising agents 
employed in the experiments unquestionably would have pro- 
duced in a more favourable season on land of that description. 
Land in a high agricultural condition, as a rule, is altogether 
unfit for the trial of manuring experiments, for soils rich in all 
the elements of fertility, and containing more plant-food than 
is requisite for the luxuriant growth of our farm crops, is not 
benefited by the application of the most valuable fertilising 
matters, which, under these circumstances, often do harm instead 
of good. On the other hand, the poorer the soil, the more 
grateful it will be for manure, and the more striking will be the 
effect which a mixture of some of the more important fertilising 
constituents is capable of producing. 
Common dung had by far the best effect on these experiments, 
for, on one of the dunged plots, the produce was increased 187 
per cent., and, on the other, 247 per cent., whilst the highest 
increase on the plots dressed with artificial manures amounted 
only to 91 per cent. 
On light land, and in a dry season, rotten dung produces a 
beneficial effect upon vegetation which cannot be expected to 
follow from the use of artificial manures. 
Apart from the direct supply of fertilising matters, a fair 
dressing of dung per acre incorporates with the land a large 
VOL. VI. — S.S. 2 E 
