80 The Pood of our Agricultural Oropi. 
three years ; the land which had been highly manured every 
fourth year giving 3i tons of hay per acre. The wheat after 
the clover upon the unmanured land was a worse crop than 
that after the fallow. 
From these results, it would appear that the roots and legumi- 
nous crops which we alternate with our corn crops are in- 
ferior to them in their capacity to collect their food from an 
ur manured soil; but when food is abundant, they have far 
greater power to make use of it than the cereal crops. In the 
22 tons of swedes grown in 1880, and in the 4 tons of clover- 
hay grown in 1882 upon the manured rotation plot, much larger 
amounts of nitrogen and minerals would be found than in a 
cereal crop. The applicatiou of a mineral superphosphate of 
lime to the root crop every fourth year produced a very marked 
effect. The last ten crops of unmanured swedes were unable to 
produce a bulb, while the employment of superphosphate gave 
a produce of 7 or 8 tons per acre ; the influence of the 
superphosphate was also very decided upon the clover crop, 
but not upon the beans. With regard to the main question, 
How far the mineral manure had enabled the leguminous plants 
to obtain their nitrogen from the atmosphere rather than from 
the soil, there is, however, at present no available evidence. 
The average of ten crops of wheat following fallow, and of ten 
following a leguminous crop, was identical — not quite 33 bushels 
per acre. Very careful samples of soil have been taken at dif- 
ferent times from all the experimental plots, and analyses have 
been made of the total nitrogen in them, and also of the nitric 
acid ; but although the results are of considerable interest, they 
do not show distinctly the differences we should expect to find 
in a soil which has not grown a leguminous crop for so many 
years, and one which has grown it every fourth year. 
Samples of soil taken to the depth of 27 inches after 
a summer fallow gave considerably more nitric acid than 
similar samples taken from the land which had grown red 
clover ; this, however, by no means proves conclusively that the 
clover had taken nitric acid from the soil, for more nitric acid 
might have been liberated in the fallow ground than in the 
clover ground. That food of some sort suitable to leguminous 
plants is accumulating in the fallow ground is shown by the 
difficulty we have in keeping them from growing on this ground : 
trefoil will come up, in more or less quantities, in the barley crop, 
where we cannot get at it ; but two years out of the four, in the 
fallow and in the turnip crop, not a plant is allowed to grow. 
It creeps along the ground, and ripens its seed before the barley 
is cut, remaining dormant in the soil until the next corn crop 
