The Dorset County Express and Agricultural Gazette.
Dorchester, Dorset, England, 1861-06-18 00:00:00

grtruttut.

biT TllB 81.:C1:1113810 11it ClOll.
The subject of tho succession or rotation of empri
has, from a etry early period, engaged a goo.' deal of
attuntiou front the culthators of the soil. It is
adanittedly oce of rut iniportente, whether viewed in
its wide influence on the pioduce of a country or as it
affects the prefits on a psi ticular farm. Writers on
the curler und practice it husbandry hare, in olden as
well ws in modern tiine., discussed the princirles en
whuh Ii their opitilon, the pr..ttice of alternating
crops WAS based, snd pre:trilied c• tom courses of
cropring in accordance with their theoretic or specula.
tire views.

1";rgil, and other Milian writers dezcrili':
Torii:us courses of crolting iu um. in their time.
very good land it was nu uncuinsuon thing to grow far
(a sort of wheat) and spring beans alternately on good
land. A triennial coune a corn, been., and pulse was
adopted on left valuable hinds. A fallow was also
made to alternate with • crop. There is no doubt that
oven prior to the Rowan period referred to, crops were
alternated in ncardanoe with ionic rules deduced front
olocrration.

In reference to this subject it may be isaid that
practice preceded theory. The crop-grower found that
the repetition of the seine crop upon the same ground
was attended with a diminution in the yield long ere
science had attempted to elucidate the subject. But,
like many other deimrtments of human industry, the
eultiention of the ...id recelved a lionerfol ;moque rn.
soon as acientitic iiiii ii to explore the principles Di
plant nutrition, and of *oil nahatn•tion.
over the variou• references made to this
iiiihjent during many centuries, we come to observe that
it midaitivil for De • e.intinental lmtanist, to
propose the first feasible explanation of the practical
advantages which experience had shown resulted from
the rotation of crops.
De Condone's theory trap, that of the various matters
which !Outs take up from the soil, the greater sart is
elaborated into their organs aud proximate compounds,
but that a portion which is unnecessary for those plants
is returned to the soil, and proves more or less inimical
to plants of the same crop or speciee.
This tscretory theory, as it was called, has caused a
good deal of discussion. At first its huportance was
esaggerated. It waa proposed awl extensively adopted
as a clear and satisfactory explanation of the advantages
of alternating crops. But the rise of a still more
plausible theory, to which we shall presently allude,
caused De Candolle's to sink into comparative obscurity
for several 3 ears. De Candulle'r views have not been
wholly abandoned ; and we think they ought not to hi.
no, for it is only by their aid that we can reasonably
account for some of the phenomena that present them•
selves in the fieid, and gsrden. De Candulle
based lib, theory on the experiments of Drug.
maims and Ilacaira, of Geneva, who found
a deposit of the nature of a bitter extract in water in
which he grew wheat, and when wheat refused to grow
in this water, beans grew lusuriantly in it. V' heat
succeeded when beans, under similar circumstances,
failed. These experiments were considered conclusive
by many farmers in this country, particularly those
claylaod farmers whose favourite practice it was to
alternate beans mud wheat, the one with the other.
The gardener and the forester observed many facts that
were in favour of his theory. In renewing vine planta-
tions an intermediate crop has been found beneficial. A
fruit tree does not succeed as well after one of the same
as of a different species. The sturdy oak, it is thought,
poisons the ground; and the use may be truly said of
the onion.

The excretory theory continue,l to be popularly re-
ceived till the publication of Liebig's celebrated work
on Agricultural Chemistry in 1840. No sooner had
that great philosopher turned his attention to the
analyses of soils and farm crops than he saw that there
masted between them • moat intimate connection. It
was found that ten or eleven mineral substances were
indispensable to the growth and full development of
phuits, and that these minerals existed in the different
farm crone in different proportions. Thin, while •
crop of wheat, producing 20001 b. of grain and 40001 b.
straw per statute acre, abstracta front the land 1371 b. of
silica, and 341 h. of potash, a crop of beans, averaging
18901 h. of grain and 3111131 h straw, carries off ISlb.
silica and 1341 b. potash. It was rewionablz.. therefore,
to suppose that if wheat were grown consecutively on
the same ground, without an adequate return of silica
in manure, the supply of this substance in the soil
would beconie so far reduced as to render it incapable
of producing • remunerative crop of wheat; and, if
instead of wheat, beans were continuously grown for •
number of years, the quantity. of potash in the soil
would soon become too limited for thy wants of the
Lean crop. It was then suggested that the .ulvantages
of alternating these two crops arose from the difference
in their chemical oompusitiou ; and that our crops
should ho alternated with each other, as far as
practicable, in accordance with their mil analyses.—
Sapid' Farmer.