Report of Experiments on the Growth of Wheat. 473 
years, that by farmyard manure was very much greater over the 
last 10 than the first 10 years of the experiments; though it 
increased in a considerably less degree during the last G as com- 
pared with the preceding 6 years. 
The total produce during the 20 years was, without manure, 
o24;;, and with farmyard manure (548g bushels of dressed corn; 
and without manure 302^, and with farmyard manure 627f cwts. 
of straw ; or almost exactly double the amount of corn, and more 
than double the amount of straw, with the farmyard manure. It 
further gave nearly double as much average annual increase of 
corn, and more than li times as much increase of straw, over the 
second as over the first 10 years ; and whilst the weight per 
bushel of the dressed corn was, without manure lower during the 
later than during the earlier half of the period, with the farmyard 
manure it was higher during the later period. 
During the whole 20 years 280 tons of farmyard manure were 
applied per acre, and there have been yielded about 18^- tons of 
corn and nearly 31^ tons of straw, equal to nearly 50 tons of total 
produce. The manure applied would not only convey to the 
land more of every constituent than was contained in the increase; 
of crop, but nearly twice as much dry organic matter, and much 
more than twice as much of nitrogen, phosphoric acid, and 
potass (and probably every other mineral constituent), as was 
contained in the total produce removed from the land. There 
has, therefore, been a great accumulation of constituents by the 
soil. No wonder, then, that the plot should yield such a much 
higher average annual produce during the later than during the 
earlier years. On the other hand, several of the artificial manures 
gave a considerably higher average produce than the farmyard 
manure ; and whilst several gave more than 50 bushels in the 
twentieth season, 1863, without any artificial supply of either 
available silica or carbonaceous organic matter during the whole 
period of the experiments, the farmyard manure gave only 44 
bushels, and also less straw. It gave, however, the highest weight 
per bushel in the series. 
A consideration of the results obtained by the other manures 
will indicate to which of the constituents of the farmyard manure 
its effects were mainly due, and which were superfluous, if not 
even in some way instrumental in limiting the productive activity 
of the constituents associated with them. 
Average Annual Produce by Mineral Manure alone. 
Plots 0, 1, and 5 had each mineral manure alone during the 
last 12 years. 
• Plot 0 was manured with a large quantity of superphosphate 
