Farmyard Manure on Potatoes._

It may be said, in this respect, that the potato is less able to utilise
the fertilising ingredients of farmyard manure than any other of the
farm crops. Yet, despite this fact, farmyard manure has been found to be
one of the best manures to apply. The reconciliation of these seemingly
contradictory statements depends on the influence exerted by the
farmyard manure on the mechanical condition of the soil, rendering it
more porous and easily permeable to the surface-roots, upon the
development of which the success of the crop so much depends. The
beneficial effect of farmyard manure is also doubtless due to the
increased temperature which large applications of it produce in a soil.

Sir J. Henry Gilbert, in his well-known Cirencester Lecture on the
Growth of Potatoes, cites several examples of the manurial treatment of
potatoes in different parts of the country. In Forfarshire, farmyard
manure or stable manure is largely employed (at the rate of 12 to 14
tons, and in some cases even 20 tons per acre), and it is also largely
supplemented by artificial manures. These latter are applied to the
extent of about 10 cwt., and consist of superphosphate, dissolved bones,
and potash salts. Six tons of potatoes are considered a fair crop. In
East Lothian the manuring is similar, with the exception that farmyard
manure is applied in even larger quantities--30 to 40 tons being often
used. Sometimes potatoes are grown with artificial manures alone. It
would seem that the usual crop of potatoes ranges from 4 to 8 tons per
acre.

_Manuring of Potatoes in Jersey._

The manuring of the potato crop, so largely grown in Jersey in the
Channel Islands, is of interest. Potatoes are there grown two or three
years, then corn, then grass for a few years, then potatoes again, no
special rotation of crops being followed. Either farmyard manure or
sea-weed is applied at the rate of 25 to 30 tons per acre, supplemented
by 8 to 12 cwt. of artificial manures.

These statements show how prevalent the practice of heavily manuring the
potato crop is.

_The Influence of Manure on the Composition of the Potato._

The influence of manure on the composition of the potato crop is of much
interest. Potatoes grown without manure, just as in the case of roots,
are found to have a larger percentage of nitrogen than potatoes grown
with manure. The effect of manuring, therefore, is to increase the
proportion of starch, whi