Experimental Plots at Rothamsted, from 1864 to 1883. 425 
In the vear 1863, the produce of the unmanured land was 
17:^ bushels; and in the worst year, 1879, it was 4| bushels. 
As previous to the year 1863, 19 unmanured crops had been 
already taken, the produce obtained was not the largest which 
had been grown ; and it is quite probable that had the season of 
1863 occurred at the beginning of the period, the yield would 
have been considerably over 20 bushels. As it was, the yield 
of 1863 was equal to the average of the first 8 years. 
In 1879 the yield was, as we have mentioned, only 4^ bushels 
per acre, with a weight of 52^ lbs. per bushel, or about one 
one-third of the average produce of the plot during the whole 
period of 40 years. The produce of the land receiving 14 tons 
of dung every year was, in 1863, 44 bushels, and in 1879 
16 bushels per acre ; a difference of 28 bushels per acre between 
the best and worst seasons. 
Contrary to what might be expected, the produce on the land 
receiving dung, while it falls greatly in yield in a bad season, 
does not rise as rapidly in yield in a very favourable season. 
This will be seen more clearly by a comparison with the 
land which receives artificial manures. We find that plot 7, 
receiving mineral manures and salts of ammonia, gave in 1879 
a crop exactly the same as that of the dung — 16 bushels per 
acre ; and we also find that the average produce of the 32 years 
is almost identical in both cases, one being 32f bushels, and 
the other 33 bushels per acre. But in the favourable season of 
1863, we find that while the dung gave only 44 bushels per 
acre, the artificial manures gave a produce of 53|^, an excess 
of nearly 10 bushels per acre. 
It is evident, therefore, that, under the most favourable cli- 
matic circumstances, the artificial manure is competent to give 
a much larger crop, both of corn and straw, than the dung. 
In the same year (1863), plot 9, which received an equivalent 
amount of nitrogen in the form of nitrate of soda to that supplied 
in the salts of ammonia on plot 7, gave a slightly higher pro- 
duce, the yield amounting to 55^ bushels per acre ; and taking the 
whole produce (corn and straw), this plot gives more than one ton 
per acre of total produce in excess of the yield on the dung plot. 
To sum up, therefore, we find that under the best artificial 
manures, 35i more bushels per acre of wheat, and nearly 2 tons 
per acre more gross produce, were grown in the most favourable 
season, as compared with the produce grown in the worst 
season. 
TTie Permanently Unmanured Plot. 
The last time this land received any manure was in 1839. 
The crop, which was then turnips, was followed bv barley, 
2 F^2 
