the largest dressing
of ammonia (500 lbs. Peruvian guano), and produced much the largest
crop; though the increase is not so great in proportion to the guano, as
where smaller quantities were used.

"The manure which produced the most profitable result, was the 100 lbs.
of plaster, on plot 2. The 200 lbs. of Peruvian guano, on plot 13, and
which cost about $6, gave an increase of 14 bushels of shelled corn, and
6 bushels of 'nubbins.' This will pay at the present price of corn in
Rochester, although the profit is not very great. The superphosphate of
lime, although a very superior article, and estimated at cost price, in
no case paid for itself. The same is true of the ashes.

"But the object of the experiment was not so much to ascertain what
manures will pay, but to ascertain, if possible, what constituents of
manures are required, in greatest quantity, for the maximum growth of
corn. * * Hitherto, no experiments have been made in this country, on
Indian corn, that afforded any certain information on this point.
Indeed, we believe no satisfactory experiments have been made on Indian
corn, in any country, that throw any definite light on this interesting
and important question. A few years ago, Mr. Lawes made similar
experiments to those given above, on his farm, at Rothamsted, England;
but owing to the coolness of the English climate, the crop did not
arrive at maturity.

"Numerous experiments have been made in this country, with guano and
superphosphate of lime; but the superphosphates used were commercial
articles, containing more or less ammonia, and if they are of any
benefit to those crops to which they are applied, it is a matter of
uncertainty whether the beneficial effect of the application is due to
the soluble phosphate of lime, or to the ammonia. On the other hand,
guano contains both ammonia and phosphate; and we are equally at a loss
to determine, whether the effect is attributable to the ammonia or
phosphate, or both. In order, therefore, to determine satisfactorily,
which of the several ingredients of plants is required in greatest
proportion, for the maximum growth of any particular crop, we must apply
these ingredients separately, or in such definite compounds, as will
enable us to determine to what particular element or compounds the
beneficial effect is to be ascribed. It was for this reason, that
sulphate of ammonia, and a purely mineral superphosphate of lime, were
used in the above experime