340 
Home Produce, Imports, Consumption, 
compared with that arrived at on the basis of the population, and 
of the amounts of the available home produce, and of the net 
imports of wheat, each year. For Scotland, and for Ireland, 
it was only possible to found an estimate on the basis of popu- 
lation, and on the amounts of the home and foreign supplies. 
On these bases we estimated the average consumption of wheat, 
in the United Kingdom collectively, to be 5^ bushels per head 
of the population per annum, during the later years to which 
our inquiry related ; and we have adopted that figure from 
that date up to the present time. This estimate, whether 
correct or not, has from that time been very generally adopted 
by other writers on the subject also. Its correctness, and its 
continued applicability, we propose to consider on the present 
occasion. 
Thus, with regard to the area under the crop, the imports, and 
the population, we adopt, without modification, the same data or 
estimates as previously : but the basis of the estimates, and the 
results arrived at, in regard to the average produce of wheat per 
acre over the United Kingdom each year, and the estimates of 
the consumption per head of the population, we propose to 
submit to examination, and to correction or otherwise, as the 
case may be. 
As already said, the estimate of the average yield of wheat per 
acre over the United Kingdom is, each year, founded on the 
average produce obtained on certain selected plots in the field 
at Rothamsted, which has now grown the crop for thirty-six 
years in succession — without manure, with farmyard-manure, 
and with various artificial manures. There has been no change 
in the treatment of the unmanured plot, or of the dunged plot, 
since the commencement of the experiments in 1843-4. There 
were, however, some changes in the manures applied to the 
various artificially manured plots during the first eight years, 
from 1844 to 1851 inclusive. But, for the period of twenty-eight 
years, from 1852 up to the present time, two of the selected 
artificially-manured plots have respectively received exactly the 
same manure each year, and the third has done so for twenty- 
five years, as described below. The selected plots were — 
Plot 3. Unmanured every year, experiment commencing 
1843-4. 
Plot 2. 14 tons farmyard-manure every year, commencing 
1843-4. 
Plot 7. Mixed mineral manure, and 400 lbs. ammonia-salts, 
each year, twenty-eight years, 1851-2, and since. 
Plot 8. Mixed mineral manure, and 600 lbs. ammonia-salts 
each year, twenty-eight years, 1851-2, and since. 
