in Stackyard Field, Wohuni. 
3 
Taking first the result of the wheat experiment, it will be 
seen how extraordinary is the influence of climate upon a crop 
which is treated in every respect in the same way year after 
year. On the unmanured plots we have three times as much 
produce in one year as we have in another. On the plot 
manured with nitrate of soda alone the produce in one year was 
10^ bushels, and in another 41 bushels per acre; thus, one 
season in this case gives four times as large a crop as another. 
Differences so great prove conclusively the necessity of carrying 
on experiments without change for a number of years, as also 
the impossibility of drawing conclusions of any value fi'om experi- 
ments which, however carefully they may have been conducted, 
have only been carried on for one or two years. 
In the fifth column of the table is given the mean produce 
of the highest and lowest crops of the ten years, while the 
sixth column gives the mean of the whole ten crops. It is the 
latter" column to which my remarks will apply. It may, however, 
be worth while to observe that the mean of the best and worst 
years frequently gives a produce which closely resembles the 
mean of the whole period. 
Omitting 8a and 9rt, which were only under experiment for 
five years, the mean of the other nine experiments gives pro- 
ducts absolutely identical ; that is, 2 6' 8 bushels both for the 
mean of the highest and lowest product and the general mean. 
The two unmanured plots, in which the difference is very small, 
give a produce of rather more than 1 7 bushels per acre, while a 
manure which supplied all the mineral ingredients for a large 
crop has produced no appreciable difference. On the other 
hand, manures such as salts of ammonia and nitrate of soda, 
which supply nitrogen, but neither phosphoric acid nor potash, 
increase the yield by 6 or 7 bushels per acre. When the 
minerals used on plot four are added to the ammonia, or to the 
nitrate of soda in plots two and three, we find the produce 
raised to 3H and 32^ bushels per acre. With the same 
mineral manures, but with twice the quantity of salts of am- 
monia and nitrate of soda, the plot which received the salts of 
ammonia yielded nearly 39 bushels per acre, and that which 
received nitrate of soda a little over 37 bushels per acre. 
Speaking in general terms, the mineral manures have added 
nothing to the unmanured crop, whUe nitrogen as ammonia or 
as nitric acid, applied without minerals, has increased the crop 
by seven bushels. When minerals have been used with the 
same nitrogen, another seven bushels have been added to the 
crop, and when twice the amount of nitrogen has been used 
with the minerals, nearly seven bushels moi'e have been added 
to the crop. In all the expex'iments the weight per bushel of 
B 2 
