Comfrey (Symphytum spp.) as a forage crop


Forbes, J.C.; McKelvie, A.D.; Saunders, P.J.C.

Herbage Abstracts 49(12): 523-539

1979


The main interest in Symphytum spp. worldwide has been, and will probably continue to be, as a silage crop. It ensiles well (Watson and Nash, 1960; Mikhkiev, Rozenberg and Il'in, 1970; Raman, 1970; Krushkova and Odegova, 1971), although serious nutrient losses occur if the herbage is not sufficiently wilted before ensiling (Van der Zweerde, (1965). Even after wilting, comfrey silage may have such a high moisture content that dry matter intake by animals is seriously restricted. Growing comfrey together with grass to provide herbage with a higher dry matter content for ensiling appears not to be successful, because the comfrey is intolerant of competition from grass (Saunders, 1977; North of Scotland College of Agriculture, 1978). When viewed as whole, the scientific literature reviewed in this article tends to indicate that while comfrey possesses some attractive features as a forage plant, it is by no means a wonder crop. Its advantages a high content of protein and certain minerals are in most circumstances outweighed by difficulties involved in its husbandry. Little research has been done on husbandry techniques and systems for comfrey, but costs of establishment, weed con trol and eventual killing for replacement by other crops are high. Husbandry trials in Scotland (Holmes, 1946), England (McClean, 1964), Germany (Stalllin, 1964) and Canada (Lachance, 1968) have led these authors to conclude that there is little place for comfrey in conventional agricultural cropping systems. It is possible, however, that at some time in the future the potential of the crop may have to be reassessed if the current interest in S. asperum in the USSR is pursued to a successful conclusion.

COMMONWEALTH
BUREAU
OF
PASTURES
AND
FIELD
CROPS
HERBAGE
ABSTRACTS
Vol.
49
December,
1979
No.
12
COMFREY
(Symphytum
spp.)
AS
A
FORAGE
CROP
J.
C.
FORBES
*
,
A.
D.
McKELVIE
*
and
P.
J.
C.
SAUNDERSt
INTRODUCTION
From
time
to
time
there
are
waves
of
interest
in
comfrey
(Symphytum
spp.)
as
a
protein-rich
forage
crop.
Its
prota-
gonists
have
often
failed
to
deal
objectively
with
its
potenti-
alities
and
limitations,
neither
has
any
account
appeared
in
the
English
language
of
the
substantial
amount
of
research
on
comfrey
which
has
been
carried
out
in
the
USSR
and
other
eastern
European
countries.
This
article
is
intended
to
meet
the
need
for
a
critical
review
of
the
scientific
literature
on
the
crop,
with
particular
reference
to
its
yield
and
chemical
composition.
TAXONOMY
Symphytum
spp.
(Boraginaceae)
are
perennial
herbaceous
plants
overwintering
as
short
stout
rhizomes.
Large,
stalked,
coarsely
hairy
leaves
arise
from
the
rhizome
in
spring,
and
later
the
aerial
stem
elongates
bearing
short-
stalked,
sessile
or
decurrent
leaves
and
a
terminal
inflorescence.
The
genus
has
been
closely
studied
in
recent
years
by
taxonomists
and
cytologists.
According
to
Tutin
(1956)
the
only
two
species
indubitably
native
to
Britain
are
S.
tuberosum
L.
and
S.
officinale
L.
S.
tuberosum
occurs
in
damp
woods
and
hedgebanks
throughout
Britain,
extending
eastwards
throughout
Europe
to
Turkey
and
the
south-
western
USSR
(Clapham,
Tutin
and
Warburg,
1962).
It
has
not
been
implicated
in
the
parentage
of
cultivated
comfreys
and
has
probably
never
itself
been
cultivated.
S.
officinale
occurs
locally
on
river
banks
and
in
wet
ditches
throughout
most
of
Europe
except
the
Arctic,
extending
to
Central
Asia
and
western
Siberia.
Gadella
and
Kliphuis
(1967)
demonstrated
the
existence
of
three
cytotypes
of
this
species.
The
diploid
(2n
=
24)
with
white
or
yellowish-white
flowers
is
the
commonest
one
in
Britain
and
occurs
in
the
rest
of
Europe
except
for
the
USSR
(Gladella,
Kliphuis
and
Perring,
1974).
The
tetraploid
(2n
=
48)
with
white,
red
or
purple
flowers
is
the
commonest
type
in
Europe
but
is
rare
in
Britain
(Perring,
1969).
The
third
cytotype
(2n
=
40),
with
purple
flowers,
is
known
only
from
the
Netherlands
(Gadella
and
Kliphuis,
1967).
Mixed
populations
of
diploids
and
tetraploids
occur
in
Europe,
but
triploids
have
only
once
been
found
and
the
cross
is
difficult
to
produce
artificially
(Basler,
1972).
Another
species,
S.
asperum
Lepechin
(S.
asperrimum
Donn)
with
2n
=
32,
is
native
to
the
Caucasus
and
is
now
widespread
in
Europe
but
rare
in
Britain.
In
Britain
Donn
(1831)
recorded
it
as
having
been
first
grown
in
the
Cambridge
Botanic
Garden
in
1801
and
cultivated
as
a
forage
crop
a
few
years
later,
but
according
to
Aiton
(1810)
it
was
introduced
in
1799
by
Conrad
Loddiges
from
St.
Petersburg
in
Russia.
Tutin
(1956)
suggested
that
the
'Russian
comfrey'
com-
monly
grown
in
Britian
is
S.
X
uplandicum
Nyman,
a
hybrid
between
S.
officinale
and
S.
asperum.
It
may
have
appeared
spontaneously
near
Bath,
but
in
view
of
the
rarity
of
S.
asperum
in
Britain
it
seems
more
likely
that
S.
X
uplandicum
has
been
introduced
from
Europe
on
several
occasions
over
the
past
150
years
(Hills,
1976).
According
to
Wade
(1958)
the
first
record
of
S.
X
uplandicum
in
culti-
vation
is
in
1827.
Some
of
these
introduced
hybrids
have
been
ascribed
to
S.
peregrinum
Ledeb.,
but
it
seems
that
this
is
simply
a
more
or
less
central
form
of
the
hybrid
swarm
S.
X
uplandicum
(Clapham,
Turin
and
Warburg,
1962).
The
hybrid
S.
officinale
(2n
=
40)
X
S.
asperum
(2n
=
32)
=
S.
X
uplandicum
(2n
=
36)
was
duplicated
experimentally
by
Gadella
and
Kliphuis
(1969).
It
is
taller
than
either
parent
and
has
dark
purple
flower
buds
and
purple
or
blue-purple
flowers.
It
is
widely
naturalized
and
is
now
probably
the
commonest
Symphytum
in
Britain.
Other
forms
of
S.
X
uplandicum
occur
in
Britain
and,
according
to
Gadella
and
Kliphuis
(1969),
these
have
2n
=
40
and
arose
as
a
cross
between
S.
officinale
(2n
=
48)
and
S.
asperum.
They
are
less
prickly
than
the
2n
=
36
cytotype
and
have
pink
flowers
and
more
strongly
decurrent
leaves.
Both
cytotypes
of
S.
X
uplandicum
are
fertile,
breeding
true
from
seed.
They
are
also
interfertile
but
the
2n
=
38
hybrid
has
not
been
found
in
nature
(Gadella,
Kliphuis
and
Perring,
1974).
Several
species
of
Symphytum
have
been,
or
are,
grown
as
forage
crops,
the
most
widely
grown
being
S.
X
uplandicum,
apparently
the
only
one
now
in
cultivation
outside
the
USSR
and
eastern
Europe.
S.
asperum
was
formerly
cultivated
in
Britain
(Darby,
1882;
Wemyss,
1882)
and
appears
at
present
to
be
the
most
widely
grown
species
in
the
USSR.
S.
officinale
is
grown
rarely
for
fodder
but
occasionally
as
a
medicinal
herb.
S.
caucasicum
Bieb.
and
S.
asperum
X
caucasicum
are
occasionally
grown
in
the
USSR
according
to
Medvedev
(1971).
Much
of
the
literature
on
comfrey
makes
no
reference
to
botanical
name,
so
that
doubt
arises
as
to
which
species
is
meant.
However,
in
this
review,
'Russian
comfrey'
is
always
assumed
to
be
S.
X
uplandicum
and
'prickly
comfrey'
S.
asperum.
BREEDING
Little
attempt
has
been
made
to
produce
improved
phenotypes
in
Symphytum.
Hills
(1976)
described
three
English
strains
of
S.
X
uplandicum
and
fifteen
clonal
selec-
tions
from
these
strains.
These
selections
carry
the
prefix
*
North
of
Scotland
College
of
Agriculture,
581
King
Street,
Aberdeen,
UK
tS.A.I.
Seeds
Development
Unit,
Ingliston,
Newbridge,
Midlothian,
UK
523
Herbage
Abstracts
1979
Vol.
49
No.
12
524
Bocking
and
form
the
major
commercial
stock
in
Britain.
Medvedev
(1971)
made
'seed
selections'
from
S.
asperum
and
S.
asperum
X
caucasicum.
He
also
explored
the
breed-
ing
possibilities
of
the
less
cold-tolerant
S.
orientale
L.
and
S.
tauricum
Willd.
(Medvedev,
1970).
Symphytum
species
are
normally
cross-pollinated.
S.
asperum
is
usually
propagated
from
seed,
which
it
produces
fairly
abundantly
(Manlov,
1970;
Moiseev
and
Votinova,
19/U).
Propagation
of
S.
X
uplandicum
is
normally
by
vegetative
means
(root
and
rhizome
cuttings)
as
this
hybrid
sets
little
seed.
YIELD
The
reputation
of
comfrey
as
a
forage
crop
has
probably
suffered
from
the
exaggerated
claims
that
have
been
made
for
its
yield
by
its
more
enthusiastic
proponents.
Yields
of
green
herbage
of
the
order
of
250
t/ha
were
claimed
around
1875
by
Doubleday
for
Symphytum
X
uplandicum
brought
to
England
from
Russia
(Hills,
1976).
One
such
yield
was
calculated
by
measuring
the
yield
from
two
heavy
cuts
in
April
and
June
and
multiplying
the
total
by
three.
The
highest
reported
yields
of
S.
X
uplandicum
were
obtained
in
Kenya
in
1955
from
a
second-year
crop
(312.7
t
green
herbage/ha)
and
in
1956
from
a
third-year
crop
in
New
Zealand
(311.6
t/ha),
but
these
figures
were
estimated
on
the
basis
of
20
'representative'
plants
selected
from
a
plot
and
were
entries
in
a
competition
to
find
the
highest
yield
(Hills,
1976).
The
highest
British
entry
was
a
yield
of
170.3
t/ha;
thus
even
a
competition
could
not
generate
the
levels
of
yield
claimed
by
Doubleday.
Scientific
measurements
and
objective
estimates
of
yield
are
presented
for
S.
X
uplandicum,
S.
asperum
and
S.
officinale
(Tables
1,
2
and
3
respectively)
grown
in
dif-
ferent
parts
of
the
world.
The
highest
individual
record
for
S
X
uplandicum
is
259.3
t
green
herbage/ha
(27.02
t
dry
matter/ha
obtained
by
Heitman
and
Miller
in
California
in
1958
(Hills,
1976).
For
S.
asperum,
a
yield
of
186.7
t/ha
was
recorded
from
a
second-year
crop
in
Uzbekistan
(Vavilov
and
Kondrat'ev,
1975).
A
record
yield
of
130.5
t
green
herbage/ha
was
reported
for
S.
officinale
in
Romania
by
Popescu,
Pais
and
Casanova
(1971).
Their
estimated
dry
matter
yield
of
32.63
t/ha
was
based
on
a
25%
dry
matter
content,
which
seems
grossly
excessive
in
view
of
other
workers'
estimates
of
10-15%.
From
the
range
of
values
in
Tables
1-3
it
can
be
con-
cluded
that
a
reasonable
expectation
of
yield
from
a
crop
of
comfrey
in
a
temperate
climate
would
be
30-60
t
green
herbage
and
3.5-7
t
dry
matter/ha
per
year.
Yield
data
for
comfrey
are
most
useful
when
they
include
comparative
data
for
well-known
forage
crops.
For
example,
Chubarova
(1974)
obtained
from
S.
asperum
in
Moscow
Province
an
average
dry
matter
yield
over
six
years
of
5.23
t/ha,
similar
to
that
obtained
from
timothy
(Phleum
pratensel.
However,
Kalinina,
D'yakonova
and
Laidinen
(1970)
found
that
in
Karelia
S.
asperum
out-
yielded
timothy.
Unfortunately
they
did
not
present
the
data
on
which
they
based
this
observation.
Table
I.
Recorded
yields
of
Symphytum
X
uplandicum
Geographical
location
Yield
(t/ha)
Fresh
Dry
Leningrad
Province,
USSR
75.9
White
Russia,
USSR
30.3
4.41
Korea
45.8
Poland
29.0
Bulgaria
28.3
West
Germany
49.9
5.20
Aberdeen,
UK
4.68
Melrose,
UK
108.7
Essex,
UK
75.6
Hampshire,
UK
40.4
6.03
Cambridge,
UK
5.64
Nova
Scotia,
Canada
11.2
Quebec,
Canada
12.9
Ontario,
Canada
32.4
Saskatchewan,
Canada
43.3
4.62
British
Columbia,
Canada
122.4
California,
USA
259.3
27.02
165.5
21.19
56.4
8.43
Southern
Brazil
63.0
Kenya
4.37
Zaire
14.6
References:
Comments
Ref.
mean
of
8
years
1
mean
of
4
years
2
mean
of
1st-2nd
years,
3
fertiliser
treatments
3
mean
of
2nd-4th
years
4
mean
of
3
sites,
1st-3rd
years
5
mean
of
2
years
6
Bocking
mixture,
mean
of
4
years
mean
of
1st-2nd
years,
2
fertiliser
treatments
7,8
9
Bocking
mixture,
mean
of
5
years
9
mean
of
2nd-4th
years
10
mean
of
2nd-3rd
years
11
3rd
year
12
mean
of
1st-2nd
years
12
mean
of
2nd,
4th
years
12
13
mean
of
3
years,
rich
soil
with
irrigation
13
young
plot,
1958
9
same
plot,
1967
9
1st
year,
1967
9
mean
of
3
sites
14
mean
of
2
years
15
16
1
Medvedev
(1974)
2
Myazhuev
and
Lapkovskaya
(1972)
3
Lee,
Kang
and
Han
(1969)
4
Tabin,
Berbe6
and
Wrgbiakowski
(1966)
5
Shchereva
et
a/.
(1965)
6
DOring
(1959)
7
Saunders
(1977)
8
North
of
Scotland
College
of
Agriculture
(1978)
9
Hills
(1976)
10
McClean
0
964)
11
Willey
and
Knight
(1962)
12
Lachance
0968)
13
Robertson
(1959)
14
Da
Silva
(1976)
15
Strange
(1959)
16
Institut
National
pour
L'Etude
Agronomique
du
Congo
Beige
(1959)
525
Comfrey
(Symphytum
spp.)
as
a
forage
crop
Table
2.
Recorded
yields
of
Symphytum
asperum
Geographical
location
Yield
(t/ha)
Fresh
Dry
Comments
Karelia,
USSR
45.8
26.8
Archangel
Province,
USSR
50.0
43.8
6.00
Komi
ASSR,
USSR
53-86
50-70
Leningrad
Province,
USSR
83.3
77-104
Moscow
Province,
USSR
41.3
4.68
103.9
46-55
Lithuania,
USSR
60-80
White
Russia,
USSR
70-80
wet
soil
up
to
90
Ukraine,
USSR
55.4
dry
year
Uzbekistan,
USSR
141.3
mean
of
1st-2nd
years
Kamchatka,
USSR
up
to
158
Sakhalin,
USSR
23-75
Ayr,
UK
24.3
mean
of
3
years
Essex,
UK
57.2
mean
of
4
years
Cambridge,
UK
2.74
mean
of
2nd-3rd
years
References:
1
Kalinina,
D'yakonova
and
Laidinen
(1970)
8
Yartiev
(1975)
2
Mikhkiev
and
Kalinina
(1975)
9
Marchyulenis
(1973)
3
Akishin
and
Simdyashkina
(1970)
10
Churilov
(1973)
4
Vavilov
and
Kondrat'ev
(1975)
5
Belyaev
(1970)
12
Holmes
(1946)
11
Khrushkova
and
Odegova
(1971)
6
Medvedev
(1974)
13
Hills
(1976)
7
Vavilov.
Edershtein
and
Solov'eva
(1973)
14
Willey
and
Knight
(1962)
mean
of
8
years
mean
of
2
years
mean
of
4
years
2nd-6th
years
mean
of
8
years
mean
of
2
years
Ref.
1
2
3
4
4
5
6
4
7
4
8
9
4
10
4
4
4
11
12
13
14
Table
3.
Recorded
yields
of
Symphyturn
officinak
Yield
(t/ha)
Fresh
Dry
Comments
78.3
mean
of
8
years
19.6
mean
of
6
years
130.5
32.63
1st
year
Geographical
location
Leningrad
Province,
USSR
Poland
Romania
Ref.
1
2
3
References:
1
Medvedev
(1974)
2
Tabin,
Herbed
and
Bobrzyriski
(1973)
3
Popescu,
Pitii
and
Casanova
(1971)
Myazhuev
and
Lapkovskaya
(1972)
compared
the
yields
of
S.
X
uplandicum,
lucerne
(Medicago
sativa),
a
mixture
of
timothy
and
red
clover
(Trifolium
pratense),
and
annually
sown
crops
of
maize
(Zea
mays)
over
four
years
in
White
Russia.
The
average
dry
matter
yields
were
4.41,
9.84,
8.89
and
6.96
t/ha
respectively.
Over
two
years
in
West
Germany
S.
X
uplandicum
yielded
on
average
less
dry
matter
per
year
(5.20
t/ha)
than
lucerne
(11.81
t/ha)
or
double
crops
of
rye
(Secale
cereale)
and
maize
(8.29
t/ha)
(During,
1959),
while
in
Kenya
it
gave,
at
4.37
t/ha,
a
yield
similar
to
that
of
lucerne
(Strange,
1959).
Willey
and
Knight
(1962)
found
that
even
the
highest
yielding
strain
in
a
S.
X
uplandicum
trial
in
England
was,
at
6.97
t
dry
matter/ha,
less
produc-
tive
than
kale
(Brassica
oleracea)
(8.54
t/ha),
timothy
(9.52
t/ha)
or
perennial
ryegrass
(Lothar;
perenne)
(11.27
t/ha)
growing
in
adjacent
trials.
In
trials
at
Aberdeen
in
Scotland,
Saunders
(1977)
found
that
in
the
year
of
establishment
the
mean
dry
matter
yields
of
S
X
uplandicum
and
L.
perenne
were
3.66
and
6.96
t/ha,
respectively;
in
the
following
year
respective
yields
were
5.69
and
8.54
t/ha
(North
of
Scotland
College
of
Agriculture,
1978).
526
Herbage
Abstracts
1979
Vol.
49
No.
12
120
100
80
F
g
reen
he
r
bag
e
y
ie
ld
(
t/
ha
)
O
S.
of
f
ieinak
S.
asperum
+
S.
X
uplandicum
A
S.
Caucusicum
A
S
Asperum
X
caucasicum
60
40
1
I
g
reen
her
bag
e
y
ie
ld
(
t/
ha
)
2
3
4
5
6
7
8
9
year
of
growth
Fig.
I
Yields
of
Symphytum
species
and
hybrids,
1965-72
(Medvedev,
1974).
140
O
West
Germany
England
A
Belgium
120
A
Caucasus
100
80
60
1
I
1
I
I
I
1
2
3
4
5
6
7
8
year
of
growth
Fig.
2
Yields
of
Symphytum
asperum
from
four
out
of
six
seed
provenances,
1966-72
(Medvedev,
1974).
40
Comfrey
(Symphytum
spp.)
as
a
forage
crop
527
Table
4.
Yields
(t/ha)
of
Symphytum
app.
from
the
same
plots
in
successive
years
Species
and
geographical
location
Fresh
or
Year
of
growth
Ref.
dry
2
3
4
5
6
S.
X
uplandicum
White
Russia,
USSR
fresh
44.0
29.2
31.9
16.3
Korea
fresh
40.5
51.1
2
Poland
fresh
7.2
43.8
22.7
20.5
3
Bulgaria
fresh
16.7
26.5
41.5
4
Aberdeen,
UK
dry
3.66
5.69
5,6
Hampshire,
UK
dry
5.24
8.32
4.38
7
Cambridge,
UK
dry
5.45
5.83
8
S.
asperum
Uzbekistan,
USSR
fresh
95.8
186.7
9
Sakhalin,
USSR
(sown
1965)
fresh
22.9
59.8
38.0
10
(sown
1966)
fresh
74.7
53.7
10
Cambridge,
UK
dry
2.26
3.21
8
S.
officinale
Poland
fresh
13.8
11.5
17.6
10.5
40.0
11
S.
asperum
X
caucasicum
Moscow
Province,
USSR
dry
1.62
5.94
10.77
3.74
12,13
References:
1
Myazhuev
and
Lapkovskaya
(1972)
2
Lee,
Kang
and
Han
(1969)
3
Tabin,
Berbee
and
Wrebiakowski
(1966)
4
Shchereva
et
al.
(1965)
5
Saunders
(1977)
6
North
of
Scotland
College
of
Agriculture
(1978)
7
McClean
(1964)
8
Willey
and
Knight
(1962)
9
Vavilov
and
Kondrat'ev
(1975)
10
KhrushIcova
and
Odegova
(1971)
11
Tabin,
Berbee
and
Bobrzydski
(1973)
12
Chubarova
and
Rybnikova
(1971)
13
Chubarova
and
Rybnikova
(1972)
Comparison
of
species,
strains
and
selections
Medvedev
(1974)
grew
five
Symphytum
species
and
hybrids
in
Leningrad
Province,
USSR
and
measured
their
yield
each
year
from
the
second
to
the
ninth
year
of
growth
(Fig.
1).
In
the
second
year
S.
asperum
and
S.
X
uplandicum
were
much
more
productive
than
the
others.
In
later
years
the
differences
were
less
marked,
but
S.
asperum
was
consistently
higher
yielding
than
S
X
uplandicum.
S.
caucasicum
was
the
least
productive
species
in
the
second
year
but
by
the
ninth
year
was
the
most
productive.
In
a
later
study
in
the
same
area
by
Medvedev
and
Sidorova
(1976),
S.
asperum
again
outyielded
S.
X
uplandicum.
Bricking
13,
a
clonal
selection
of
S.
asperum,
was
includ-
ed
in
a
yield
trial
over
several
years
by
Hills
(1976)
in
England,
together
with
ten
S.
X
uplandicum
selections.
Its
yield
was
close
to
the
mean
for
S.
X
uplandicum
but
far
below
that
of
the
highest
yielding
selection.
Willey
and
Knight
(1962)
obtained
an
average
dry
matter
yield
over
two
years
from
S.
asperum
cv.
Rocking
13
which
was
less
than
half
the
average
yield
for
seven
strains
and
clonal
selections
of
S.
X
uplandicum.
Bocking
13
may
not,
how-
ever,
be
representative
of
S.
asperum
as
a
whole.
The
ten
clonal
selections
of
S.
X
uplandicum
compared
by
Hills
(1976)
ranged
in
fresh
yield
from
33.9
to
85.5
t/ha.
The
best
were
Bocking
4,
Bricking
14,
Socking
16
and
Bocking
17.
Willey
and
Knight
(1962)
also
found
Bocking
14
and
Bricking
17
to
be
relatively
high
yielding,
but
obtained
low
yields
from
Socking
4.
These
selections
were
neither
greatly
nor
consistently
higher
yielding
than
the
more
variable
strains
from
which
they
were
developed.
McClean
(1964)
obtained
similar
yields
from
three
strains
and
the
selection
Socking
4.
In
Poland,
two
ecotypes
of
S.
X
uplandicum
from
Lodz
and
Tarnow
grown
in
a
trial
at
Lublin
did
not
differ
in
yield
(Tabin,
Berbed
and
Wrgbiakowski,
1966).
Ecotypes
of
S.
officinale
from
kodz,
Tarnow
and
Nicdrzwica
did,
however,
show
significant
yield
differences
(Tabin,
Berbee
and
Bobrzythki,
1973).
Medvedev
(1974)
established
plots
from
six
seed
provenances
of
S.
asperum
and
measured
their
yields
from
the
second
year
onwards
(Fig.
2).
There
were
some
con-
sistent
differences
between
provenances,
but
the
yield
of
a
provenance
in
the
second
year
of
growth
was
not
necessarily
indicative
of
its
long-term
productivity.
He
also
studied
the
variation
within
a
single
provenance
from
the
Caucasus
and
found
a
range
in
average
yields
over
seven
years
from
nine
seed
selections
of
59.4
to
97.8
t
green
herbage/ha.
Effect
of
stand
age
on
yield
When
the
yields
from
a
set
of
plots
are
measured
over
a
number
of
years,
the
effect
of
stand
age
is
unfortunately
confounded
with
the
effect
of
weather
and
probably
also
with
management
in
different
years.
In
general,
however,
the
highest
yields
are
obtained
in
the
second
or
third
year
of
growth.
Year-to-year
differences
in
yield
of
Symphytum
spp.
as
measured
by
Medvedev
(1974)
are
shown
in
Figs.
1
and
2;
other
studies
are
summarized
in
Table
4.
In
crops
grown
from
seed,
as
is
usual
with
S.
asperum
in
the
USSR,
the
first
year
yield
is
generally
very
small
and
is
frequently
not
recorded.
The
high
first
year
yields
recorded
from
Uzbekistan
(Vavilov
and
Kondrat'ev,
1975)
and
Sakhalin
(Khrushkova
and
Odegova,
1971)
are
therefore
difficult
to
explain,
unless
they
pertain
to
the
first
year
of
utilization
rather
than
of
growth.
In
crops
grown
from
root
or
rhizome
cuttings,
as
is
usual
in
S.
X
uplandicum,
the
first
year
yield
is
appreciable,
but
almost
always
lower
than
in
the
second
year.
After
the
second
or
third
year
yields
fall
rapidly
to
a
low
level
(McClean,
1964;
Chubarova
and
Rybnikova,
1972)
or
fluctuate
about
a
value
somewhat
below
the
maximum
(Medvedev,
1974).
In
Moscow
Province,
Vavilov,
Dotsenko
and
Dotsenko
(1974)
in
the
fourth
year
of
utilization
of
S.
asperum
obtained
yields
18-23%
greater
than
in
the
third
year.
In
the
same
region
the
average
yield
of
S.
X
uplandicum
over
the
rust
three
years
was
6.81
t
dry
matter/ha,
but
over
the
next
three
years
was
only
3.65
t/ha
(Chubarova,
Vorob'ev
and
Rybnikova,
1970;
Chubarova,
1974).
528
Herbage
Abstracts
1979
Vol.
49
No.
12
Table
5.
Dry
matter
yield
of
Symphytum
X
uplandicum
and
Lolium
perenne
and
a
mixture
of
these
species
Dry
matter
yield
(t/ha)
Contribution
by
Symphytum
Cutting
date
Symphytum
Lolium
to
mixture
X
uplandicum
perenne
Mixture
L.S.D.
(P
=
0.05)
13
Jul.
1976
1.50
3.07
3.85
0.91
18
Aug.
1976
1.31
1.70
1.68
0.30
19
7
Nov.
1976
0.84
2.18
2.21
0.20
9
Total
first
year
3.66
6.96
7.74
2
June
1977
2.32
2.94
2.31
0.94
35
20
July
1977
3.00
2.67
3.42
.
0.53
21
8
Nov.
1977
0.37
2.93
2.82
0.70
10
Total
second
year
5.69
8.54
8.55
References:
Saunders
(1977)
North
of
Scotland
College
of
Agriculture
(1978)
McClean
(1964)
attributed
the
drop
in
yield
of
S.
X
uplandicum
in
the
fourth
year
of
a
trial
in
England
to
a
devastating
attack
by
the
rust
fungus
Melampsorella
symphyti.
Comfrey
rust
appears
to
be
the
only
important
disease
of
the
crop
and
attacks
S.
asperum
and
S.
officinale
as
well
as
S.
X
uplandicum.
The
mycelium
perennates
in
the
rhizome,
and
uredospores
are
produced
on
the
leaves
in
early
summer
(Wilson
and
Henderson,
1966).
There
appear
to
be
differences
between
clonal
selections
of
S.
X
uplandicum
in
their
susceptibility
to
the
disease
(Hills,
1976).
In
trials
in
Poland
the
maximum
yield
of
S.
officinale
was
not
achieved
until
the
sixth
year
(Tabin,
Berbec
and
Bobrzyriski,
1973).
Vavilov
and
Kondrat'ev
(1975)
give
an
instance
of
a
thirty-year-old
crop
of
S.
asperum
yielding
55.60
t
green
herbage/ha.
The
only
published
study
in
which
the
respective
effects
of
age
and
year
are
distinguished
is
that
on
S.
asperum
in
Sakhalin
by
Khrushkova
and
Odegova
(1971).
From
the
data
in
Table
4
it
is
clear
that
the
superiority
of
1966
over
1967
as
a
growing
year
was
a
more
important
determinant
of
yield
than
the
age
of
the
stand
at
the
time.
Effect
of
water
supply
on
yield
Darby
(1882)
described
S.
asperum
as
a
drought-tolerant
species,
but
in
the
USSR
drought
is
reported
to
have
adverse
effects
both
on
yield
(Vavilov,
Dotsenko
and
Dotsenko,
1974)
and
on
longevity
(Tanfil'ev,
1975).
Yields
of
S.
X
uplandicum
are
seriously
reduced
by
drought
(New
South
Wales
Department
of
Agriculture,
1959;
Van
der
Zweerde,
1965;
Lachance,
1968).
In
a
pot
experiment
Tabin
and
Herbed
(1968)
obtained
a
higher
yield
of
S.
X
uplandicum
over
three
years
with
the
soil
at
60%
of
field
capacity
than
at
45%
or
75%
of
field
capacity.
In
Hong
Kong
the
growth
of
a
trial
crop
of
S.
X
uplandicum
was
retarded
by
the
onset
of
the
wet
season,
and
finally
the
plants
died,
the
crown
and
roots
having
rotted
(Hong
Kong
Department
of
Agriculture,
Fisheries
and
Forestry,
1959).
Effect
of
fertilizers
on
yield
The
highest
yields
of
comfrey
have
been
obtained
with
heavy
fertilizer
application,
as
in
S.
X
uplandicum
trials
in
California
reported
by
Hills
(1976)
(see
Table
I).
Experi-
ments
in
different
parts
of
the
world
have,
however,
pro-
duced
inconclusive
and
often
conflicting
evidence
on
the
effect
of
fertilizers
on
comfrey
yield.
Strange
(1959)
found
in
Kenya
that
application
of
12
t/ha
of
farmyard
manure
plus
188
kg/ha
of
triple
super-
phosphate
made
no
difference
to
the
yield
of
S.
X
uplandicum.
By
contrast,
Lee,
Kang
and
Han
(1969)
in
Korea
observed
large
yield
increases
with
a
combination
of
farmyard
manure
and
inorganic
fertilizers.
Response
to
very
high
fertilizer
levels
was
better
in
the
second
than
in
the
first
year.
Miring
(1959)
in
West
Germany
obtained
a
higher
dry
matter
yield
of
S.
X
uplandicum
with
75
kg
N,
62.5
kg
P2O5
and
90
kg
K
2
0/ha
(4.57
t/ha)
than
with
the
phos-
phate
and
potassium
fertilizers
alone
(3.66
t/ha).
Increasing
the
nitrogen
level
to
100
or
125
kg/ha
produced
no
further
yield
increases.
In
Poland
the
average
fresh
yield
of
S.
X
uplandicum
in
the
second,
third
and
fourth
years
was
24.6
t/ha
with
application
of
30
kg
N/ha
and
33.4
t/ha
with
application
of
60
kg
N/ha
with
50
kg
P
2
O
5
and
120
kg
K20/ha
supplied
for
both
treatments
(Tabin,
Berbe6
and
Wrgbiakowski,
1966).
In
the
absence
of
phosphate
and
potassium
fertilizers,
Saunders
(1977)
obtained
a
dry
matter
yield
of
3.27
t/ha
with
62
kg
N/ha
and
4.05
t/ha
with
150
kg
N/ha.
S.
asperum
dry
matter
yield
increased
from
3.90
t/ha
with
no
fertilizer
to
4.80
t
with
30
kg
N,
45
kg
P
2
O
5
and
60
kg
K
2
0/ha.
Doubling
the
rates
of
phosphate
and
potassium
application
increased
the
yield
to
5.30
t/ha
(Vavilov
and
Kondrat'ev,
1975).
Evidence
that
comfrey
is
particularly
responsive
to
potassium
fertilizers
was
obtained
by
Chubarova,
Vorob'ev
and
Rybnikova
(1970)
who
obtained
a
higher
dry
matter
yield
of
S.
X
uplandicum
with
100
kg
N,
60
kg
P
2
O
5
and
218
kg
K
2
0/ha
(4.40
t/ha)
than
with
120
kg/ha
each
of
N,
P
2
O
5
and
K
2
O
(3.74
t/ha).
Application
of
gypsum
did
not
increase
the
yield
of
S
X
uplandicum
in
Kenya
although
the
yield
of
lucerne
was
increased
(Strange,
1959).
Calcium
carbonate
at
four
rates
had
no
effect
on
S.
X
uplandicum
yield
in
a
pot
experiment
by
Tabin
and
BerbeC
(1968).
Ikeda
et
al.
(1964)
obtained
increased
yields
of
S.
X
uplandicum
in
pots
following
the
addition
of
cobalt,
molybdenum
or
boron
to
the
soil,
but
not
using
copper,
manganese
or
zinc.
Effect
of
competing
species
on
yield
Comfrey
is
said
to
be
intolerant
of
weed
competition
(Hills,
1976),
but
few
quantitative
studies
have
been
done
on
the
influence
of
other
species
on
comfrey
yield.
Saunders
(1977)
grew
S.
X
uplandicum
alone
or
in
mixture
with
Lolium
perenne.
First
and
second
year
yields
are
shown
in
Table
5.
The
results
clearly
indicate
that
S.
X
uplandicum
is
not
sufficiently
vigorous
to
hold
its
own
against
a
competitive
grass
sward.
It
does,
however,
contri-
bute
usefully
to
herbage
yield,
at
least
in
the
first
two
years.
Effect
of
plant
density
on
yield
In
a
trial
in
the
Komi
ASSR
reported
by
Vavilov
and
Kondrat'ev
(1975),
S.
asperum
gave
the
highest
yield
at
the
widest
plant
spacing
(60
X
60
cm
or
70
X
50
cm).
The
lower
plant
density
was
more
than
compensated
for
by
the
much
greater
individual
plant
weight,
as
shown
in
Fig.
3.
3
100
80
2
yield
(y
=
118.6-0.00153x)
60
individual
plant
weight
(y
=
12014
_
1
5855)
x
40
E
20
0
0
2
30
:J.
t3111'.
7
:.
aAt
in
div
idua
l
p
lan
t
fres
h
we
ig
ht
(
kg
)
Vont.
(Symphytum
app.)
as
a
forage
crop
529
g
reen
her
bag
e
y
ie
ld
(t
/
ha
)
20
30
40
50
60
plant
density
(x
1000/ha)
Fig.
3
Effect
of
plant
density
on
yield
and
individual
plant
weight
of
Symphytum
awerum
(Vavilov
and
Kondrat'ev,
1975).
70
60
second
year
50
40
first
year
30
0
20
10
0
1
I I
10
20
30
40
0
60
plant
density
(X
1000/ha)
Fig.
4
Effect
of
plant
density
on
yield
of
Symphytum
X
uplandicum
(12c,
Kang
and
Han,
1969).
Herbage
Abstracts
1979
Vol.
49
No.
12
530
In
the
Netherlands,
however,
Van
der
Zweerde
(1965)
found
that
the
reverse
was
true
for
S.
X
uplandicum,
in
that
a
45
X
45
cm
spacing
gave
higher
hields
than
a
90
X
90
cm
spacing,
except
in
very
dry
weather.
Similar
results
were
obtained
in
Bulgaria
by
Shchereva
et
al.
(1965),
who
found
an
even
higher
yield
at
20
X
20
cm
than
at
45
X
45
cm
spacing.
Lee,
Kang
and
Han
(1969)
in
Korea
obtained
a
similar
effect
in
the
first
year,
but
in
the
second
year
they
observed
a
reduced
yield
only
at
the
lowest
density
(Fig.
4).
Effect
of
cutting
regime
on
yield
The
average
dry
matter
yield
of
S.
X uplandicum
over
two
years
in
West
Germany
was
significantly
affected
by
the
stage
of
growth
at
which
the
first
cut
of
the
season
was
taken.
The
annual
yield
was
3.81
t/ha
from
5
or
6
cuts
beginning
at
the
rosette
stage,
5.44
t/ha
from
3
or
4
cuts
beginning
just
before
flowering,
and
8.00
t/ha
from
3
cuts
beginning
when
the
plants
were
in
full
flower
(Diking,
1959).
With
S.
asperum
in
Sakhalin,
however,
the
date
of
the
first
cut
had
no
effect
on
the
total
annual
yield
(Khrushkova
and
Odegova,
1971).
Medvedev
and
Sidorova
(1976)
found
that
in
both
S.
asperum
and
S.
X
uplandicum
the
yield
was
strongly
influenced
by
the
cutting
regime
in
the
previous
year.
Yields
were
30-35%
greater
from
plots
cut
only
once
in
the
previous
year
than
from
plots
cut
three
times.
A
similar
effect
on
S.
X
uplandicum
yield
was
noted
by
Chubarova,
Vorob'ev
and
Rybnikova
(1970).
CHEMICAL
COMPOSITION
The
earliest
recorded
chemical
analysis
of
comfrey
was
performed
by
Voelcker
(1871),
who
partitioned
the
dry
matter
of
Symphytum
asperum
into
"nitrogenous
organic
compounds"
(29%),
"non-nitrogenous
organic
compounds"
(51%)
and
ash
(20%).
The
non-nitrogenous
fraction
was
separable
into
"oil
and
chlorophyll"
(2%),
"gum,
mucilage
and
a
little
sugar"
(14%)
and
"cellulose"
(35%).
Of
the
nitrogenous
fraction
12%
was
soluble
and
17%
insoluble.
More
recent
data
on
proximate
analysis
of
herbage
from
Symphytum
spp.
are
summarized
in
Table
6.
The
standard
format
used
by
the
UK
Ministry
of
Agriculture,
Fisheries
and
Food
(1975)
has
been
adopted,
with
conversion
of
original
data
where
necessary.
Dry
matter
contents
of
fresh
comfrey
range
in
Table
6
from
about
110
to
200
g/kg,
similar
to
those
of
green
forage
crops
such
as
cabbage,
kale
and
rape
or
the
leaves
of
sugar
beet
and
turnips,
but
somewhat
lower
than
that
of
grazed
grass.
The
dry
matter
content
of
comfrey
silage
depends
on
the
length
of
time
for
which
the
crop
is
wilted
before
ensiling,
the
method
of
ensilage
and
whether
or
not
molasses
or
other
materials
are
added
to
raise
the
carbo-
hydrate
level
for
fermentation.
It
may,
however,
be
as
low
as
135
g/kg
(Hills,
1976),
considerably
below
what
is
normally
regarded
as
a
desirable
level
for
grass
silage.
The
following
factors
have
been
shown
to
have
no
effect
on
proximate
constituents
of
Symphytum
herbage:
trace
element
application
(Ikeda
et.
at,
1964),
soil
moisture
content
and
calcium
carbonate
level
(Tabin
and
Berbed
1968)
Strains
or
ecotypes
differ
little
except
possibly
in
protein
content
(Tabin,
Herbed
and
Wrcbiakowski,
1966;
Medvedev,
1974).
Fertilizer
application
may
affect
protein
content
but
not
other
constituents
(Tabin,
Berbed
and
Wrgbiakowslci,
1966).
Protein
Much
of
the
interest
in
comfrey
as
a
forage
crop
has
centred
on
its
protein
content.
The
highest
single
record
for
crude
protein
is
434
g/kg
DM
in
the
leaf
blades
of
S.
asperum
ip
spring
1970
in
Moscow
Province,
USSR
(Vavilov,
Edel'shtein
and
Solov'eva,
1973),
but
Table
6
suggests
that
normal
values
are
in
the
range
150-275
g/kg
DM.
This
is
rather
higher
than
grass
and
comparable
with
legumes
such
as
lucerne
and
red
clover.
Estimates
of
the
digestibility
of
the
crude
protein
for
ruminants
range
widely
from
38
to
82%.
The
digestible
crude
protein
content
normally
ranges
from
65
to
187
g/kg
DM,
though
a
rabbit-digestible
crude
protein
content
of
201
g/kg
DM
has
been
recorded
by
Han,
Kim
and
Lee
(1968).
There
is
little
suggestion
from
Table
6
of
any
difference
in
protein
content
between
S.
X
uplandicum
and
S.
asperum.
Medvedev
(1974)
found
that
over
eight
or
nine
years,
the
average
crude
protein
contents
of
these
species
and
of
S.
officinale,
S.
caucasicum
and
S.
asperum
X
caucasicurn
were
all
about
170
g/kg
DM.
No
differences
in
crude
protein
content
were
found
between
clonal
selections,
strains
or
ecotypes
of
S.
X
uplandicum
by
Willey
and
Knight
(1962),
McClean
(1964)
or
Tabin,
Berbec
and
Wrebiakowski
(1966).
Seed
provenances
of
S.
asperum
did,
however,
show
considerable
differences
in
crude
protein
content
(Medvedev,
1974).
The
digestible
crude
protein
content
of
S.
asperum
was
slightly
depressed
by
the
application
of
30
kg
N,
45
kg
P205
and
60
kg
K
2
0/ha,
but
doubling
the
phosphate
and
potassium
rates
had
no
further
effect.
The
yield
of
digest-
ible
crude
protein
was,
however,
increased
from
490
kg/ha
with
no
fertilizer
to
540
kg/ha
at
the
lower
rate
and
590
kg/ha
at
the
higher
rate
(Vavilov
and
Kondrat'ev,
1975).
No
effect
of
fertilizer
on
the
crude
protein
content
of
S.
X
uplandicum
was
found
by
Tabin,
Berbe6
and
Wrgbiakowslci
(1966)
or
by
Chubarova,
Vorob'ev
and
Rybnikova
(1970).
Saunders
(1977)
measured
the
crude
protein
content
of
S.
X
uplandicum
and
Latium
perenne
grown
alone
and
in
mixture
at
cuts
in
August
and
November
of
the
year
of
establishment.
As
shown
in
Table
7,
nitrogen
fertilizer
increased
the
crude
protein
content
of
comfrey
and
of
grass,
each
grown
alone,
at
the
August
cut
but
not
at
the
later
cut;
this
response
was
not
found
in
comfrey
grown
together
with
grass.
Crude
protein
yields
were
substantially
increased
by
fertilizer
application.
If
a
typical
mean
crude
protein
content
over
the
year
is
200
g/kg
DM,
a
crude
protein
yield
of
0.8-1.5
t/ha
can
be•
expected
from
comfrey
under
normal
conditions.
Recorded
yields
(Table
8)
are,
however,
in
a
somewhat
lower
range
of
0.2-1.2
t/ha
and
are
similar
to
those
obtainable
from
lucerne
or
other
legumes,
or
from
good
quality
grass.
The
crude
protein
yield
of
9.786
t/ha
from
S.
officinale
recorded
by
Popescu,
Pitis
and
Casanova
(1971)
must
be
regarded
with
extreme
scepticism,
as
it
is
based
on
a
mean
DM
content
of
25%
and
a
mean
crude
protein
content
of
300
g/kg
DM.
In
general,
the
crude
protein
content
of
comfrey
declines
with
age.
Medvedev
(1974)
found
this
effect
to
be
more
marked
in
S.
X
uplandicum
than
in
S.
asperum,
as
shown
in
Fig.
5.
Strange
(1959)
obtained
a
crude
protein
content
of
234
g/kg
DM
in
the
first
year,
but
only
173
g/kg
DM
in
the
second
year
of
a
S.
X
uplandicum
crop.
Willey
and
Knight
(1962)
observed
a
similar
drop
from
252
to
209
g/kg
DM,
between
the
second
and
third
years.
By
contrast,
McClean
(1964)
found
little
difference
in
crude
protein
content
in
the
second,
third
and
fourth
years.
All
available
data
indicate
a
decline
in
crude
protein
content
with
maturity
(Table
9).
There
is,
however,
much
less
agreement
about
the
seasonal
crude
protein
trend
in
successive
cuts
where
the
crop
is
not
allowed
to
grow
to
an
advanced
stage
of
maturity.
Crawley
(1942),
McClean
(1946)
and
Saunders
(1977)
found
no
consistent
seasonal
trend.
Willey
and
Knight
(1962)
found
a
depression
in
crude
protein
content
in
the
middle
of
the
growing
season,
but
Shchereva
et.
at
(1965)
found
exactly
the
opposite.
The
results
of
Tabin,
Berbed
and
Wrsbiakowski
(1966)
show
a
modest
rise
throughout
the
growing
season,
whereas
Medvedev
(1974)
found
that
the
mean
crude
protein
content
at
the
second
cut
was
little
more
than
half
that
at
the
first
cut.
In
summer,
the
leaves
of
S.
asperum
are
much
richer
in
crude
protein
than
the
stems,
and
in
spring
and
autumn
the
leaf
blades
contain
more
than
the
petioles
(Vavilov,
Edel'shtein
and
Solov'eva,
(1973).
The
same
is
true
of
the
spring
leaves
of
S.
X
uplandicum
(Shchereva
et
al.,
1965).
Few
efforts
have
been
made
to
determine
the
true
protein
content
of
comfrey
herbage.
Kellner
(1926)
estimated
that
true
protein
in
S.
asperum
accounted
for
60%
of
the
crude
protein
in
green
herbage,
but
80%
of
that
in
hay.
Vavilov,
Edel'shtein
and
Solov'eva
(1973)
found
that
on
average
the
true
protein
content
of
S.
asperum
was
about
78%
of
the
crude
protein.
Albumins
and
globulins
made
up
about
38%,
prolamin
4%
and
glutelins
14%
of
the
true
protein.
Shchereva
et
at
(1965)
hydrolysed
the
protein
of
S.
X
uplandicum
and
of
lucerne
and
compared
the
amino-acid
composition
of
the
two
species.
They
had
similar
contents
of
alanine,
proline
and
valise,
but
S.
X
uplandicum
had
relatively
large
amounts
of
aspartic
acid,
glutamic
acid,
isoleucine/leucine,
lysine,
phenylalanine
and
serine.
Co
m
f
rey
(
Sy
mp
hy
tu
m
spp.
)
as
a
f
orag
e
c
rop
Table
6.
Proximate
chemical
analysis
of
forage
from
Symphytum
app.
Species
and
comments
DM
g/kg
ME
MJ/kg
DM
DCP
g/kg
DM
CP
Analysis
of
DM
(g/kg)
EE
CF
NFE
Ash
GE
MJ/kg
DM
Q
=
ME
GE
DOMD
%
Digestibility
coefficients
(ruminant
unless
otherwise
stated)
CP
EE
CF
NFE
Ref.
S.
X
uplandicum
green
herbage
255
98
1
275
2
124
274
24
121
395
185
16.5
3
7.6
104
150
17
123
434
276
14.1
0.54
48
0.69
0.65
0.46
0.71
4
169
31
166
413
221
15.6
5
115
255
138
369
6
150
210
1
7
mean
of
2
years
142
108
203
33
113
442
209
15.9
0.53
8
151
10.2
187
227
54
42
464
213
16.3
0.63
63
0.82
0.52
0.97
0.80
9
164
23
116
429
269
14.4
10
mean
of
3
years
157
191
11
204
168
56
77
515
191
16.7
12
117
74
195
180
38
13
mean
of
3
years
138
161
16
250
381
192
15.8
14
240
21
118
467
154
16.8
15
155
46
100
553
146
17.1
15
mean
of
3
years
1
1
1
156
17
193
465
169
16.2
16
165
17
mean
of
4
years
152
96
18
mean
of
9
years
170
168
19
112
20
218
21
140
485
136
17.1
21
166
22
12.4
65
I
1
1
134
77
0.58
23
for
rabbits
186
10.3*
201
236
51
129
404
180
16.4
0.63
71
0.85
0.74 0.84
0.89
24
for
pigs
0.50 0.80
0.85
0.67
25
silage
135
340
192
21
S.
asperum
green
herbage
120
8.5
130
217
25
150
433
175
16.5
0.52
54
0.60
0.67
0.47
0.74
3,26,27
189
102
165
0.62
28
205
29
mean
of
6
years
119
171
30
mean
of
9
years
170
197
19
121
206
33
144
524
93
18.0
31
silage
180
160
32
hay
850
8.8
141
244
32
135
413
176
16.7
0.53
54
0.58
0.71
0.18
0.85
26
890
255
30
122
429
163
16.9
33
meal
427
6.4
94
206
25
102
530
136
17.0
0.38
40
0.46
0.65
0.61
0.43
34
S.
officinale
green
herbage
287
31
160
348
175
17.0
35
mean
of
8
years
171
190
19
Abbreviations:
CF
-
crude
fibre;
CP
-
crude
protein;
DCP
-
digestible
crude
protein;
DM
-
dry
matter;
DOMD
-
digestible
organic
matter
in
dry
matter;
EE
-
ether
extract,
GE
-
gross
energy;
ME
-
metabolisable
energy;
NFE
--
nitrogen
free
extract
*digestible
energy
532
Herbage
Abstracts
1979
Vol.
49
No.
12
References:
1
Crawley
0942)
2
Malaya
Department
of
Agriculture
(1956)
3
Woodman
(1957)
4
Elliott
and
Croft
(1958)
5
Van
Rensburg
(1958)
6
Daring
(1959)
7
Institut
National
pour
('Etude
Agronomique
du
Congo
8
Strange
(1959)
Beige
(1959)
9
Patel,
Patel
and
Shukla
(1962)
10
Ikeda
et
al.
(1964)
11
McClean
(1964)
12
Shchereva
et
al.
(1965)
13
Van
der
Zweerde
(1965)
14
Tabin,
Herbed
and
Wrebiakowski
(1966)
15
Lachance
(1968)
16
Tabin
and
Herbed
(1968)
17
Chubarova,
Vorob'ev
and
Rybnikova
(1970)
18
Myazhuev
and
Lapkovskaya
(1972)
19
Medvedev
(1974)
20
Tascenco,
Isar
and
Eeredean
(1974)
21
Hills
(1976)
22
Saunders
(1977)
23
North
of
Scotland
College
of
Agriculture
(1978)
24
Han,
Kim
and
Lee
(1968)
25
Heitman
and
Oyarzun
(1971)
26
Kellner
(1926)
27
UK
Ministry
of
Agriculture,
Fisheries
and
Food
(1975)
28
Kalinina
(1970)
29
Marchyulenis
(1973)
30
Chubarova
(1974)
31
Vavilov
and
Kondrat'ev
(1975)
32
Mikhkiev,
Rozenberg
and
ll'in
(1970)
33
Holmes
(1946)
34
Astakhov
(1970a)
35
Popescu,
Pitis
and
Casanova
(1971)
Table
7.
Content
and
yield
of
crude
protein
in
comfrey(Symphytum
X
uplandicum),
grass
(Lolium
perenne)
and
a
comfrey-
grass
mixture,
at
two
nitrogen
fertilizer
levels
crude
protein
content
(g/kg
DM)
yield
(kg/ha)
N
applied
(kg/ha)
62
150
62
150
Cut
18
August
comfrey
144
179
161
271
grass
84
I
1 1
90
258
mixture
103
293
comfrey
134
135
grass
88
124
Cut
7
November
comfrey
176
163
124
146
grass
144
145
291
338
mixture
310
339
comfrey
153
138
grass
154
144
Reference:
Saunders
(1977)
Table
8.
Some
recorded
crude
protein
yields
from
Symphytum
app.
mean
crude
protein
Species
Geographical
no.
of
yield
Ref.
location
years
kg/ha
England
2
233
England
3
1
151
2
S.
X
uplandicum
Moscow
Province,
USSR
3
I
121
3
White
Russia,
USSR
4
446
4
Moscow
Province,
USSR
2
1
049
5
S.
asperum
Moscow
Province,
USSR
6
892
6
Archangel
Province,
USSR
4
1
000
7
References:
1
Willey
and
Knight
(1962)
5
Vavilov,
&lershtein
and
Solov'eva
(1973)
2
McLean
(1964)
6
Chubarova
(1974)
3
Chubarova,
Vorob'ev
and
Rybnikova
(1970)
7
Vavilov
and
Kondrat'ev
(1975)
4
Myazhuev
and
Lapkovskaya
(1972)
Consfrey
(Symphytum
spp.)
as
a
forage
crop
533
250
S.
asperunt
S
X
uplandieum
200
.°4
C
C
O
C
O
u
so
100
I
I
I
I
I I
1
2
3
4
5
6
7
8
9
age
(years)
Fig.
5
Effect
of
age
on
crude
protein
content
of
Symphytum
spp.
(Medvedev,
1974).
250
S.
asperunt
O
S.
X
uplandicum
—12oo
O
00
AC
C
C
.0
150
100
1
1
2
3
4
5
6
7
8
9
age
(years)
Fig.
6
Effect
of
age
on
crude
fibre
content
of
Symphytum
spp.
(Medvedev,
1974).
Herbage
Abstracts
1979
Vol.
49
No.
12
534
growth
stage
Table
9.
Crude
protein
content
of
Symphytum
spp.
at
different
growth
stages
Crude
protein
content
(g/kg
DM)
stem
early
full
rosette
elongation
flower
bud
flower
flower
Ref.
seed
S.
X
uplandicum
348
303
244
180
154
S.
asperum
210
200
150
2
220
133
3
244
172
98
4
216
188
5
305
187
6
S.
officinale
308
265
7
References:
1
DOring
(1959)
5
Khrushkova
and
Odegova
(1971)
2
Moiseev
et
at
(1963)
6
Vavilov,
Edel'shtein
and
Solov'eva
(1973)
3
Kharkevich
(1966)
7
Popescu,
Pitis
and
Casanova
(1971)
4
Astakhov
(1970b)
Chekalinskaya
and
Chekhova
(1970)
found
that
S.
asperum
was
rich
in
lysine,
phenylalanine
and
threonine,
but
Egorova
(1973)
could
detect
no
major
differences
in
amino-acid
composition
between
S.
asperum
and
red
clover
or
lucerne.
Hills
(1976)
gives
data
showing
S.
X
uplandicum
to
be
fairly
rich
in
isoleucine,
lysine,
methionine
and
tryptophan.
This
was
confirmed
for
lysine
but
not
for
methionine
by
Saunders
(1977).
Oil
and
fat
Values
in
Table
6
for
ether
extract
range
from
16
to
54
g/kg
DM,
with
a
digestibility
of
46-85%.
Comfrey
is
thus
similar
in
oil
and
fat
content
to
other
green
forages.
Strange
(1959)
obtained
a
lower
ether
extract
in
the
second
year
than
in
the
first
year
of
a
S.
X
uplandicum
crop.
Growth
stage
had
no
influence
on
ether
extract
in
S.
officinale
(Popescu,
Pitis
and
Casanova,
1971).
Tabin,
Berbed
and
Wrebiakowski
(1966)
noted
a
modest
rise
in
ether
extract
through
the
growing
season
in
regrowths
of
S.
X
uplandicum,
but
no
such
effect
was
observed
by
Willey
and
Knight
(1962)
or
by
Shchereva
et
al
(1965).
Nitrogen-free
extractive
substances
Most
values
for
nitrogen-free
extract
in
Table
6
are
in
the
range
400-500
g/kg
DM,
comparable
with
other
green
forages.
Khrushkova
and
Odegova
(1971)
found
the
total
sugar
content
of
S.
asperum
herbage
to
be
70-80
g/kg
DM.
Fibre
Crude
fibre
contents
of
Symphy
turn
spp.
in
Table
6
range
from
about
100
to
200
g/kg
DM
rather
lower
than
grass
or
lucerne.
Patel,
Patel
and
Shukla
(1962)
obtained
an
abnormally
low
value
of
42
g/kg
DM
and
Tabin,
Berbed
and
Wrebiakowski
(1966)
a
rather
high
mean
of
250
g/kg
DM
over
three
years.
Medvedev
(1974)
found
that
S.
X
uplandicum
had
a
consistently
lower
fibre
content
than
S.
asperum
(see
Fig.
8).
Differences
between
seed
provenances
of
S.
asperum
in
crude
fibre
were
less
marked
than
in
crude
protein.
Crude
fibre
content
increases
with
age,
as
shown
in
Fig.
6.
Strange
(1959)
also
found
a
higher
fibre
content
in
S.
X
uplandicum
in
the
second
year
than
in
the
first.
Within
the
growing
season,
fibre
content
increases
with
maturity
(Table
10)
as
in
other
herbage
crops,
although
this
was
not
evident
in
S.
officinale
analysed
by
Popescu,
Pitis
and
Casanova
(1971).
Medvedev
(1974)
found
that
on
average
the
fibre
content
of
S.
asperum
was
higher
at
the
second
than
at
the
first
cut,
but
no
consistent
seasonal
trend
in
the
fibre
content
of
S.
X
uplandicum
regrowths
was
noted
by
Willey
and
Knight
(1962),
Shchereva
et
at
(1965)
or
Tabin,
Berbed
and
Wrebiakowski
(1966).
Digestibility
No
general
pattern
emerges
from
the
digestibility
co-
efficients
listed
in
Table
6.
Crude
fibre
digestibility
co-
efficients,
for
example,
range
from
18%
(Kellner,
1926)
to
97%
(Patel,
Patel
and
Shukla,
1962).
Total
ruminant-
digestible
organic
matter
is
in
the
range
40-63%
of
dry
matter,
except
for
an
in
vitro
digestibility
of
77%
recorded
for
S.
X
uplandicum
in
the
summer
of
its
second
year
(North
of
Scotland
College
of
Agriculture,
1978).
Lehmann
(1944)
found
that
the
digestibility
of
S.
X
uplandicum
for
pigs
decreased
with
crop
maturity
from
73%
of
total
organic
matter
at
the
rosette
stage
to
as
low
as
55%
in
the
flowering
stage.
Saunders
(1977)
estimated
the
digestibility
of
S.
X
uplandicum
for
ruminants
using
the
MAD-fibre
technique,
obtaining
values
of
70%
dry
matter
in
August
and
59%
in
November
of
the
first
year.
Park
et
al.
(1969)
found
little
change
in
digestibility
of
S.
X
uplandicum
in
three
successive
regrowths,
but
obtained
much
higher
digestibilities
from
plots
cut
at
intervals
of
25
days
than
from
plots
cut
at
intervals
of
30
to
45
days.
Gross
and
metabolizable
energy
All
the
gross
and
metabolizable
energy
values
in
Table
6
have
been
calculated
from
total
and
digestible
nutrients,
respectively,
using
the
formulae
given
by
the
UK
Ministry
of
Agriculture,
Fisheries
and
Food
(1975),
except
for
those
values
obtained
calorimetrically
by
Han,
Kim
and
Lee
(1968)
for
S.
X
uplandicum
fed
to
rabbits.
Gross
energy
contents
are
in
the
range
14-18
MJ/kg
DM,
and
metaboliz-
able
energy
contents
in
the
range
6.3-12.4
MJ/kg
DM.
Taking
10
MJ/kg
DM
as
a
standard,
comfrey
can
be
expected
to
yield
35
000-70
000
MJ/lia
of
metabolizable
energy,
a
sufficient
maintenance
allowance
for
10-20
cattle
of
300
kg
body
weight
for
100
days.
Vitamins
Table
11
gives
some
recorded
values
of
the
content
of
ascorbic
acid,
carotene
and
folic
acid
in
the
herbage
of
Symphytum
spp.
Carotene
levels,
on
which
there
is
the
greatest
amount
of
data,
are
similar
to
those
in
grasses
and
legumes.
Carotene
and
ascorbic
acid
contents
decline
sharply
in
the
course
of
the
growing
season
in
S.
asperum,
though
carotene
contents
do
so
only
in
the
early
part
of
the
season
(Edel'shtein
and
Solov'eva,
1974).
Shchereva
et
al.
(1965)
found
that
S.
X
uplandicum
had
a
somewhat
lower
ascorbic
acid
content
in
flowering
than
in
vegetative
plants
of
S.
officinale.
The
vitamin
content
of
leaf
blades
of
S.
asperum
is
about
ten
times
that
of
leaf
stalks
and
stems
(Edel'shtein
and
Solov'eva,
1974).
Hills
(1976)
presents
data
showing
S.
X
uplandicum
to
contain
vitamin
B12
at
levels
around
5µg/kg
DM.
He
des-
cribes
an
experiment
by
Wokes
demonstrating
the
almost
unique
capacity
of
comfrey
to
take
up
this
vitamin
through
its
roots.
However,
in
view
of
the
particular
susceptibility
of
comfrey
to
soil
contamination
(Strange,
1959),
data
on
vitamin
B
12
in
the
plant
must
be
interpreted
with
caution.
Alkaloids
Symphytum
spp.,
in
common
with
other
members
of
the
Boraginaceae,
contain
pyrrolizidine
alkaloids
similar
in
structure
to
the
hepatotoxic
alkaloids
of
Senecio
spp.
Furuya
and
Araki
(1968)
found
that
roots
of
Symphytum
officinale
had
a
total
alkaloid
content
of
2.26
g/kg
DM.
Later,
Furuya
and
Hikichi
(1971)
isolated
0.67
g/kg
symphytine
and
0.50
g/kg
echimidine
from
S.
offficinale
roots.
Long
(1976)
determined
the
pyrrolizidine
alkaloid
content
of
the
leaves
of
several
S.
X
uplandicum
clonal
selections,
S.
asperum,
S.
officinale
and
S.
caucasicum
and
Comfrey
(Symphytum
spp./
as
a
forage
crop
535
Table
10.
Crude
fibre
content
of
Symphytum
spp.
at
different
growth
stages
Crude
fibre
content
(g/kg
DM)
stem
early
full
Ref.
growth
stage
rosette
elongation
flower
bud
flower
flower
seed
S.
X
uplandicum
104
122
151
209
222
1
S.
asperum
145
170
190
2
186
213
3
105
145
182
4
S.
officinale
156
163
5
References:
1
Dbring
(1959)
2
Moiseev
et
at.
(1963)
3
Kharkevich
(1966)
4
Astakhov
(1970b)
5
Popescu,
Pitis
and
Casanova
(1971)
Table
11.
Vitamin
content
of
herbage
from
Symphytum
app.
content
(mg/kg
DM)
ascorbic
acid
carotene
folic
acid
Ref.
S.
X
upbndicum
357
543
2
S.
asperum
750
400
309
450
207
200
500
3
4
5
6
7
S.
officinale
150
8
References:
I
Shchereva
et
al
(1965)
2
Chubarova,
Vorob'ev
and
Rybnikova
(1970)
3
Holmes
(1946)
4
Astakhov
(1970a)
5
Kolomiitseva
et
at
(1970)
6
Moiseev
and
Aleksandrova
(1970)
7
Vavilov
and
Kondrat'ev
(1975)
8
Popescu,
Pitis
and
Casanova
(1971)
found
a
range
of
0.1-0.6
g/kg
DM.
Neither
injection
of
alkaloids
nor
prolonged
feeding
of
comfrey
to
rats
produced
any
hepatic
lesions.
He
concluded
that
there
was
no
toxicity
hazard
in
feeding
Symphytum
spp.
to
livestock.
Recently,
however,
Hirono,
Mori
and
Haga
(1978)
found
that
S.
officinale
leaves
fed
to
rats
at
rates
of
16
or
33%
of
the
diet
produced
cancerous
tumours
of
the
liver,
and
that
the
roots
were
carcinogenic
at
rates
as
low
as
0.5%
of
the
diet.
Although
no
cases
of
liver
poisoning
of
human
beings
consuming
comfrey
as
a
tonic
or
medicinal
herb
have
been
reported,
its
use
in
this
way
can
no
longer
be
considered
completely
safe
(British
Medical
Journal,
1979).
Minerals
Most
values
in
Table
6
for
the
ash
content
of
comfrey
herbage
are
in
the
range
125-225
g/kg
DM
much
higher
than
the
normal
range
for
grasses
and
legumes.
This
cer-
tainly
reflects
the
natural
richness
of
comfrey
in
mineral
elements,
but
to
some
extent
it
may
be
a
consequence
of
the
liability
of
comfrey
leaves
to
become
contaminated
with
soil.
At
one
sampling
period,
Strange
(1959)
found
that
soil
accounted
for
13.5%
of
the
dry
weight
of
S.
X
uplandicum
herbage,
but
only
1.7%
of
the
dry
weight
of
lucerne.
The
highest
recorded
ash
content
for
comfrey
is
416
g/kg
DM
in
S.
X
uplandicum
at
the
stem
elongation
stage
(Dbring,
1959).
Ash
content
does
not
vary
in
any
consistent
way
with
growth
stage
in
S.
X
uplandicum
(During,
1959),
S.
asperum
(Moiseev
et
aL,
1963;
Kharkevich,
1966;
Astakhov,
1970b;
Khrushkova
and
Odegova,
1971;
Vavilov
and
Kondrat'ev,
1975)
or
S.
officinale
(Popescu,
Piti§
and
Casanova,
1971).
There
are
no
great
differences
in
ash
content
in
successive
regrowths
of
S.
X
uplandicum
(Willey
and
Knight,
1962;
Shchereva
et
aL,
1965;
Tabin,
Berbed
and
Wrebiakowslci,
1966)
or
S.
asperum
(Medvedev,
1974).
Five
species
and
hybrids
of
Symphytum
in
a
single
trial
all
had
similar
ash
contents
(Medvedev,
1971).
Mineral
analyses
of
Symphytum
spp.
are
summarized
in
Table
12.
They
show
the
crop
to
be
rich
in
potassium,
calcium,
phosphorus,
iron
and
copper
relative
to
most
herbage
species.
Mineral
content
is
not
greatly
influenced
by
growth
stage
in
S.
asperum
(Khrushkova
and
Odegova,
1971)
or
S.
officinale
(Popescu,
Pitts
and
Casanova,
1971).
Successive
regrowths
did
not
differ
in
potassium,
calcium
or
phosphorus
content
in
S.
X
uplandicum
(Willey
and
Knight,
1962;
Saunders,
1977)
or
S.
asperum
(Medvedev,
1974).
Willey
and
Knight
(1962)
found
that
magnesium
content
was
higher
in
September
than
in
June,
and
Saunders
(1977)
found
it
to
be
lower
in
November
than
in
August,
as
shown
in
Table
13.
Sodium,
manganese,
zinc
and
copper
contents
were
higher
in
November
than
in
August.
Nitrogen
fertilizer
had
no
effect
on
mineral
content.
Ikeda
et
at
(1964)
found
that
by
supplying
the
appropriate
trace
element
to
the
soil
they
could
enrich
the
herbage
of
S.
X
uplandicum
in
manganese,
molybdenum
or
cobalt
but not
in
zinc,
boron
or
copper.
Table
13
also
shows
the
comparative
mineral
contents
of
S.
X
uplandicum,
Lolium
perenne
and
a
mixture
of
the
two
species
(Saunders,
1977;
North
of
Scotland
College
of
Agriculture,
1978).
Comfrey
can
usefully
contribute
calcium,
phosphorus
and
copper
as
well
as
protein
(Table
7)
to
a
grass
sward,
at
least
in
its
first
two
years.
Latyshenko
(1975)
has
recommended
the
sowing
of
S.
asperum
and
other
species
to
improve
the
quality
of
grasslands
on
peaty
forest
soils.
Table
12.
Mineral
content
of
Symphytum
app.
Species
and
comments
S.
X
uplandieum
green
herbage
SiO
2
53.5
K
Ca
20.2
g/kg
DM
Cl
5.7
Na
Mg
Fe
Mn
mg/kg
DM
B
Cu
Mo
Co
Ref.
1
mean
of
2
years
29.2
63.0
23.1
5.3
20.2
3.90
2
94
3
233
30
31
19.3
0.47
0.01
4
4.3
6.5
5
39.1
49.5
3.6
6
41.6
25.8
3.4
4.57
201
7
65.8
15.1
5.9
1.14
2.60
159
84
10.0
8
45.1
12.1
4.7
0.61
2.60
68
60
8.2
0.18
9
S.
asperum
green
herbage
10.1
4.7
10
19.1
5.1
11
49.6
9.6
5.4
12
37.5
8.0
13
silage
156
40
4.0
0.20
14
hay
1.5
0.02
15
12.0
3.3
13
S.
officinale
green
herbage
9.3
96.7
7.9
8.3
1.99
2.35
16
25.6
13.1
2.3
0.98
85
7
References:
I
Patel,
Patel
and
Shukla
(1962)
2
Willey
and
Knight
(1962)
3
Chamberlain
and
Searle
(1963)
4
Ikeda
etal.
(1964)
5
Han,
Kim
and
Lee
(1968)
6
Myazhuev
and
Lapkovskaya
(1972)
7
Hills
(1976)
8
Saunders
(1977)
9
North
of
Scotland
College
of
Agriculture
(1978)
10
Holmes
(1946)
11
Khrushkova
and
Odegova
(1971)
12
Medvedev
(1974)
13
Vavilov
and
Kondrat'ev
(1975)
14
Kolomiitseva
et
al.(1970)
15
Kochanov
and
Simakova
(1970)
16
Popescu,
Pitia
and
Casanova
(1971)
ff
erb
a
ge
A
b
st
r
act
s
1979
V
ol
.
49
N
o
.
12
K
Ca
g/kg
DM
P
Na
Mg
Mn
mg/kg
DM
Zn
Cu
72.1
15.7
5.9
0.43
3.06
134
67
7.5
34.8
3.9
3.5
1.08
2.31
254
55
5.9
41.9
6.4
4.1
1.10
2.53
244
62
7.5
59.6
14.5
5.9
1.85
2.15
183
100
12.5
36.3
3.5
4.2
1.27
1.84
240
52
8.8
35.3
4.2
4.9
1.31
1.84
240
54
10.1
45.1
12.1
4.7
0.61
2.60
68
60
8.2
21.7
3.6
3.2
0.78
1.75
108
53
5.0
31.2
5.8
3.7
1.15
2.11
117
56
5.7
Cutting
Year
date
18
August
1976
7
November
1977
20
July
Herbage
comfrey
grass
mixture
comfrey
grass
mixture
comfrey
grass
mixture
Cornfrey
(Symphytum
spp.)
as
a
forage
crop
537
Table
13.
Mineral
content
of
comfrey
(Symphytum
X
uplandicum),
grass
(Lolium
perenne)
and
a
comfrey-grass
mixture
References:
Saunders
(1977)
North
of
Scotland
College
of
Agriculture
(1978)
PALATABILITY
When
wilted
or
ensiled
the
leaves
of
Symphytum
spp.
are
readily
eaten
by
all
classes
of
livestock,
but
when
fresh
the
leaves
are
unpalatable,
especially
to
cattle,
probably
owing
to
the
hispid
leaf
surface
(New
South
Wales
Depart-
ment
of
Agriculture,
1959;
Van
der
Zweerde,
1965).
Wilson
(1961a)
observed
that
Hereford
steers
found
S.
X
uplandicum
less
attractive
than
grasses
including
Dactylis
glomerata
and
Festuca
rubra
or
legumes
such
as
lucerne
and
sainfoin
(Onobrychis
viciifolia).
It
was,
however,
eaten
with
relish
by
sheep,
and
also
by
Holstein
heifers
after
they
had
grown
accustomed
to
it
(Wilson,
1961b).
The
fresh
leaves
of
S.
X
uplandicum
are
quite
palatable
to
pigs
and
poultry
(Van
der
Zweerde,
1965;
Hills,
1976)
but
not
to
rabbits
(Han,
Kim
and
Lee,
1968).
CONCLUSIONS
The
main
interest
in
Symphytum
spp.
worldwide
has
been,
and
will
probably
continue
to
be,
as
a
silage
crop.
It
ensiles
well
(Watson
and
Nash,
1960;
Mikhkiev,
Rozenberg
and
Il'in,
1970;
Raman,
1970;
Krushkova
and
Odegova,
1971),
although
serious
nutrient
losses
occur
if
the
herbage
is
not
sufficiently
wilted
before
ensiling
(Van
der
Zweerde,
(1965).
Even
after
wilting,
comfrey
silage
may
have
such
a
high
moisture
content
that
dry
matter
intake
by
animals
is
seriously
restricted.
Growing
comfrey
together
with
grass
to
provide
herbage
with
a
higher
dry
matter
content
for
ensiling
appears
not
to
be
successful,
because
the
comfrey
is
intolerant
of
competition
from
grass
(Saunders,
1977;
North
of Scotland
College
of
Agriculture,
1978).
When
viewed
as
whole,
the
scientific
literature
reviewed
in
this
article
tends
to
indicate
that
while
comfrey
possesses
some
attractive
features
as
a
forage
plant,
it
is
by
no
means
a
wonder
crop.
Its
advantages
-
a
high
content
of
protein
and
certain
minerals
-
are
in
most
circumstances
outweighed
by
difficulties
involved
in
its
husbandry.
Little
research
has
been
done
on
husbandry
techniques
and
systems
for
comfrey,
but
costs
of
establishment,
weed
con-
trol
and
eventual
killing
for
replacement
by
other
crops
are
high.
Husbandry
trials
in
Scotland
(Holmes,
1946),
England
(McClean,
1964),
Germany
(Sta.blin,
1964)
and
Canada
(Lachance,
1968)
have
led
these
authors
to
conclude
that
there
is
little
place
for
comfrey
in
conventional
agricultural
cropping
systems.
It
is
possible,
however,
that
at
some
time
in
the
future
the
potential
of
the
crop
may
have
to
be
reassessed
if
the
current
interest
in
S.
asperum
in
the
USSR
is
pursued
to
a
successful
conclusion.
REFERENCES
AITON,
W.
T.
(1810)
Hortus
Kewensis,
1,
294.
AKISHIN,
L.;
SIMDYASHKINA,
N.
(1970)
Opyt
vozdely-
vaniya
novykh
kormovykh
rastenii
v
Arkhangel'skoi
Oblasti
[Cultivation
trials
of
new
todder
plants
in
Archangel
Province].
Sth
Symposium
on
New
Silage
Plants,
Leningrad,
Part
1,
7-8.
ASTAKHOV,
I. I.
(1970a)
Itogi
raboty
po
izucheniyu
okopnika
kak
kormovogo
rasteniya
[A
study
of
comfrey
as
a
fodder
plant].
5th
Symposium
on
New
Silage
Plants,
Leningrad,
Part
I,
67-68.
ASTAKHOV,
I.
I.
(1970b)
Okopnik
[Comfrey].
Leningrad
USSR.
BASLER,
A.
(1972)
(Cytotaxonomische
Untersuchungen
an
der
Boraginaceen-Gattung
Symphytum
L.:
Unter-
suchungen
an
iiberwiegend
norddeutschen
Pflanzen
der
Arten
S.
asperum
Lepech.,
S.
officinale
L.
and
S.
X
uplandicum
Nym.
[Cytotaxonomic
investigations
in
the
genus
Symphytum
L.
(Boraginaceae):
Investiga-
tions
on
mainly
north
German
plants
of
the
species
S.
asperum
Lepech.,
S.
officinale
L.
and
S.
X
uplandicum
Nym.
]
BotanischeJahrbacher,
92,508-553.
BELYAEV,
A.
G.
(1970)
Opyt
vyrashchivaniya
novykh
vidov
silosnykh
rastenii
v
sovkhoze
`Sysol'skif
Komi
ASSR.
[Cultivation
trials
of
new
species
of
silage
plants
on
Sysol'skii
State
Farm,
Komi
ASSR.]
.
5th
Symposium
on
New
Silage
Plants,
Leningrad,
Part
I,
13-14.
BRITISH
MEDICAL
JOURNAL
(1979)
Reply
to
query,
3
March
1979,
p.598.
CHAMBERLAIN,
G.
T.;
SEARLE,
A.
J.
(1963)
Trace
elements
in
some
East
African
soils
and
plants.
II.
Manganese.
East
African
Agriculture
and
Forestry
Journal,
29,
114-119.
CHEKALINSKAYA,
I.
I.;
CHEKHOVA,
A.
N.
(1970)
Aminokislotnyi
sostav
belkov
okopnika
shershavogo,
mapal'ego
kornya
i
katrana
serdtselistnogo
[Amino-
acid
composition
of
proteins
of
Symphytum
asperum,
Rhaponticum
carthamoides
and
Crambe
cordifolia].
5th
Symposium
on
New
Silage
Plants,
Leningrad,
Part
I,
57-58.
CHUBAROVA,
G.
V.
(1974)
[A
study
of
promising
perennial
silage
plants].
Sbornik
Nauchnykh
Rabot,
Vsesoyuznyi
Institut
Kormov,
1974(9),
168-175.
CHUAROVA,
G.
V.;
RYBNIKOVA,
V.
A.
(1971)
[Charac-
teristics
of
root
system
development
in
perennial
herbage
species].
Luga
i
Pastbishcha,
1971(5),
30-31.
CHUBAROVA,
G.
V.;
RYBNIKOVA,
V.
A.
(1972)
Formi-
rovanie
listovoi
poverkhnosti,
kornevoi
sistemy
i
urozhaya
mnogoletnikh
silosnykh
rastenii
[The
development
of
leaf
surface,
root
system
and
yield
in
perennial
silage
plants.]
.
Sel'skokhozyaistvennaya
Biologiya,
7,
98-102.
CHUBAROVA,
G.
V.;
VOROB'EV,
S.
S.;
RYBNIKOVA,
V.
A.
(1970)
Produktivnost'
perspektivnykh
silosnykh
rastenii,
kormovye
dostoinstva
i
nekotorye
voprosy
538
Herbage
Abstracts
1979
Vol.
49
No.
12
agrotekhniki
ikh
vyrashchiVaniya
na
korm
[Producti-
vity
of
prospective
silage
plants,
their
nutritive
value
and
some
aspects
of
the
techniques
of
their
cultivation
as
crops].
5th
Symposium
on
New
Silage
Plants,
Leningrad,
Part
I,
4244.
CHURILOV,
A.
K.
(1973)
Introdulctsiya
v
Belorussiyu
krupnotravnykh
mnogoletnikov
iz
prirodnoi
flory
i
ikh
znachenie
v
kormoproizvodstve
[Introduction
to
White
Russia
of
perennial
herbage
species
from
the
natural
flora
and
their
importance
in
fodder
produc-
tion].
Poleznye
Rasteniya
Pribaltiiskilth
Respublik
i
Belontssii,
1973,
137-143.
CLAPHAM,
A.
R.;
TUTIN,
T.
G.,
WARBURG,
E.
F.
(1962)
Flora
of
the
British
Isles.
2nd
Edition.
Cambridge,
UK;
Cambridge
University
Press.
CRAWLEY,
.1.
K.
(1942)
Prickly
comfrey
-a
neglected
fodder
crop.
Scottish
Farmer,
28
February,
1942.
DARBY,
.1.
(1882)
On
green
or
fodder
crops
not
commonly
grown,
which
have
been
found
serviceable
for
stock-
feeding.
Journal
of
the
Royal
Agricultural
Society
of
England,
2nd
Series,
18,
114-153.
DA
SILVA,
V.
de
P.
S.
(1976)
ConsideracSes
sobre
a
cultura
do
comfrey
[Consideration
of
the
cultivation
of
comfrey].
Anuario
Tecnico
do
Institute
de
Pesquisas
Zootecnicas
Francisco
Osorio,
3,
609-615.
DONN,
J.
(1831)
Hortus
Cantabrigensis,
65.
DORING,
W.
(1959)
Der
Comfreyanbau
[Comfrey
cultiva-
tion].
Deutsche
Landwirtschaft,
10(2),
62-65.
EDEL'SHTEIN,
M.
M.;
SOLOV'EVA,
I.
V.
(1974)
Soder-
zhanie
karotina
i
askorbinovoi
kisloty
v
silosnykh
kul'turakh
[The
carotene
and
ascorbic
acid
contents
of
silage
crops]
.
Doklady
Timiryazevskoi
Serskokhozyai-
stvennoi
A
kademii,
204,
51-54.
EGOROVA,
A.
A.
(1973)
[Amino-acid
composition
of
some
fodder
plants].
Biologicheskie
i
K
hozyaistvennye
Osobennosti
Novykh
Kormovykh
Rastenii
v
Usloviyakh
Karelii,
Petrosavodsk,
58-61.
ELLIOTT,
R.
C.;
CROFT,
A.
G.
(1958)
Digestion
trials
on
Rhodesian
feedstuffs.
Rhodesia
Agricultural
Journal,
55,
40-49.
FURUYA,
T.;
ARAKI,
K
(1968)
Studies
on
constitutents
of
crude
drugs.
I.
Alkaloids
of
Symphytum
officinak.
Chemical
and
Pharmaceutical
Bulletin,
16,
2512-2516.
FURUYA,
T.;
HIKICHI,
M.
(1971)
Alkaloids
and
triter-
penoids
of
Symphytum
officinak.
Phytochemistry,
10,
2217-2220.
GADELLA,
T.
W.
J.;
KLIPHUIS,
E.
(1967)
Cytotaxonomic
studies
in
the
genus
Symphytum.
I.
Symphytum
officinak
in
the
Net
herlands.
Proceedings
-
Koninklifice
Nederlandse
Akademle
van
Wetenschappen,
Series
C,
70,
378-391.
GADELLA,
T.
W.
J.;
KLIPHUIS,
E.
(1969)
Cytotaxonomic
studies
in
the
genus
Symphytum.
II.
Crossing
experi-
ments
between
Symphytum
officinak
L.
and
Symphytum
asperum
Lepech.
Acta
Botanica
Neerlandica,
18,
544-549.
GADELLA,
T.
W.
J.:
KLIPHUIS,
E.;
PERRING,
F.
H.
(1974)
Cytotaxonomic
studies
in
the
genus
Symphytum.
VI.
Some
notes
on
Symphytum
in
Britain.
Acta
Botanica
Neerlandica,
23,
433437.
HAN.
I.
K.;
KIM,
K.
I.;
LEE,
K.
S.
(1968)
[Comparative
studies
of
the
nutritive
value
of
Russian
comfrey
(Symphytum
peregrinum)
and
kale
Brassica
oleracea
var.
acephala)
for
growing
rabbits]
.
Research
Reports
-
Office
of
Rural
Development,
Suwon,
11(4),
89-95.
HEITMAN,
H.;
OYARZUN,
S.
E.
(1971)
Comfrey
as
a
feed
for
swine.
California
Agriculture,
25(1),
7-8.
HILLS,
L.
D.
(1976)
Comfrey:
past,
present
and
future.
London,
UK:
Faber
and
Faber.
HIRONO,
i.;
MORI,
H.;
HAGA,
M.
(1978)
Carcinogenic
activity
of
Symphytum
officinak.
Journal
of
the
National
Cancer
Institute,
61,
865-869.
HOLMES,
W.
(1946)
Prickly
comfre
y.
Agriculture,
London,
52,
515-516.
HONG
KONG
DEPARTMENT
OF
AGRICULTURE,
FISHERIES
AND
FORESTRY
(1959)
Fodder
crop
trials.
Annual
Report
1958-59,
36-38.
IKEDA,
M.;
KUROZUMI,
IC.;
TSUBOTA,
J.;
MATSUMURA,
H.
(1964)
[Effect
of
trace
elements
for
dallisgrass
and
Russian
comfrey].
Journal
of
the
Japanese
Society
of
Grassland
Science,
10(2),
100-104.
INSTITUT
NATIONAL
POUR
L'ETUDE
AGRONO-
MIQUE
DU
CONGO
BELGE
(1959)
Multiplication
de
Symphytum
peregrinum.
Rapport
Annuel
pour
PExercice
1958,
383.
KALININA,
S.I.;
D'YAKONOVA,
A.P.;
LAIDINEN,
KH.E.
(1970)
Produktivnost'
novykh
dlya
Karehi
mnogoletnykh
kormovykh
rastenii
[Productivity
of
perennial
fodder
plants
new
to
Karelia].
5th
Symposium
on
New
Silage
Plants,
Leningrad,
Part
I,
19-20.
KALININA,
Z.
G.
(1970)
Novye
silosnye
rasteniya
v
Novosibirskoi
Oblasti
[New
silage
plants
in
Novosibirsk
Province].
5th
Symposium
on
New
Silage
Plants,
Leningrad,
Part
1,20-22.
KELLNER,
0.
(1926)
The
scientific
feeding
of
animals.
2nd
Edition.
London,
UK:
Duckworth.
KHARKEVICH,
S.
S.
(1966)
Poleznye
rasteniya
prirodnoi
flory
Kavkaza
i
ilch
introduktsiya
na
Ukraine.
Kiev,
USSR
Naukova
Dumka.
KHRUSHKOVA,
N.
G.;
ODEGOVA,
A.
A.
(1971)
Okopnik
na
Sakhalin
[Comfrey
in
Sakhalin].
Trudy
Saki:a-
linskogo
Icompleksnogo
Nauchno-issledovatePskogo
Institute,
1971(23),
175-179.
KOCHANOV,
N.
E.;
SIMAKOVA,
T.
V.
(1970)
Obmen
mikroilementov
v
organizme
korov
pri
kormlenii
silosom
iz
novykh
kul'tur
[Metabolism
of
trace
elements in
cows
fed
on
silage
of
new
crops].
5th
Symposium
on
New
Silage
Plants,
Leningrad,
Part
I,
61.
KOLOMIITSEVA,
T.
F.;
MOISEEV,
K.
A.;
ALEKSANDROVA,
M.
1.;
FROLOVA,
N.
P.
(1970)
Silosuemost'
i
pitatel'nye
dostoinstva
silosa
iz
novykh
silosnykh
rastenii
[Ensiling
and
nutritive
quality
of
silage
from
new
silage
plants]
.
5th
Symposium
on
New
Silage
Plants,
Leningrad,
Part
I,
4749.
LACHANCE,
L.
(1968)
La
consoude
Quaker
[Quaker
comfrey
]
.
Agriculture,
Montreal,
25(4),
29-34.
LATYSHENKO,
M.
D.
(1975)
[Enrichment
of
forest
grasslands
with
fodder
plants]
.
Nauchnye
Trudy,
Ukminskaya
SePskokhozyaistvennaya
Akademiya,
146,
109-112.
LEE,
K.
S.;
KANG,
C.
J.;
HAN,
I.
K.
(1969)
[Effects
of
planting
density
and
amount
of
fertiliser
on
the
growth
and
yield
of
Russian
comfrey
(Symphytum
pere-
grinum)].
Research
Reports
-
Office
of
Rural
Development,
Suwon,
12(4),
8348.
LEHMANN,
F.
(1944)
Die
Lehre
von
der
Ftitterung
and
Mast
des
Schweines
[Methods
of
feeding
and
fattening
pigs]
.
Berlin,
Germany.
LONG,
D.
B.
(1976)
The
alkaloid
content
of
comfrey.
In
HILLS,
L.
D.
(1976)
Comfrey:
past,
present
and
future.
London,
UK:
Faber
and
Faber,
229-237.
MALAYA
DEPARTMENT
OF
AGRICULTURE
(1956)
Pasture,
fodder
and
feeds.
Annual
Report
1956,
73-74.
MANLOV,
A.
I.
(1970)
Semennaya
produktivnost'
rastenni
v
nekotozylch
fitotsenozakh
Bol'shogo
Kavkaza
[
Seed
production
of
plants
in
some
plant
communities
of
the
Greater
Caucasus]
.
5th
Symposium
on
New
Silage
Plants,
Leningrad,
Part
I,
27-28.
MARCHYULENIS,
V.
I.
(1973)
Perspektivnye
vysoko-
belkovye
kormovye
-
silosnye
rasteniya
v
Litovskoi
SSR.
[Promising
high-protein
fodder
and
silage
plants
in
Lithuanian
SSR.]
Poleznye
Rasteniya
Pribaltiiskikh
Respublik
i
Belorussii,
1973,
107-109.
McCLEAN,
S.
P.
(1964)
Russian
comfrey.
Experimental
Husbandry,
10,
46-51.
MEDVEDEV,
P.
F.
(1970)
Iskhodnyi
material
i
metody
selektsii
okopnika
[Basic
material
and
methods
for
selection
in
comfrey].
5th
Symposium
on
New
Silage
Plants,
Leningrad,
Part
I,
68-69.
MEDVEDEV,
P.
F.
(1971)
Vidy
okopnika,
imeyushchie
kormovoe
znachenie
[
Species
of
comfrey
used
as
forage
plants]
.
Rastitel'ne
Resursy,
7,
49-55.
MEDVEDEV,
P.
F.
(1974)
Prodolzhitel'nost'
khozyaist-
vennogo
ispol'zovaniya
i
urozhainost'
pyati
vidov
okopnika
(The
duration
of
economic
utilisation
and
yields
of
five
species
of
comfrey
I.
Restiternie
Resursy,
10,
598-605.
MEDVEDEV,
P.
F.;
SIDOROVA,
A.
(1976)
Urozhai
zavicit
of
chisla
ukosov
v
predydushchem
godu
[Yields
depend
on
number
of
cuts
in
the
preceding
year].
Korma,
1976(2),
44.
MIKHKIEV,
A.
I.;
KALININA,
S.
I.
(1975)
[Effect
of
weather
conditions
on
productivity
of
perennial
fodder
plants
introduced
into
Karelia].
Estestvennaya
Sreda
i
Comfrey
(Symphytum
spp.)
as
a
forage
crop
539
Biologicheskie
Resursy
Krainogo
Severe,
Leningrad,
3843.
MIKHKIEV,
A.
I.;
ROZENBERG,
V.
M.;
IL'IN,
N.
G.
(1970)
Khimicheskoe
konservirovanie
zelenoi
massy
novykh
silosnykh
rastenii
[Chemical
conservation
of
fresh
matter
of
new
silage
plants]
.
5th
Symposium
on
New
Silage
Plants,
Leningrad,
Part
I,
63-64.
MOISEEV,
K.
A.
et.
al.
(1963)
None
perspektivnye
silosnye
rasteniya
v
Komi
ASSR.
[New
promising
silage
plants
in
the
Komi
ASSR].
Syktyvkar
Komi
Knozhnoe
izdatel'stvo.
MOISEEV,
K.
A.;
ALEKSANDROVA,
M.
I.
(1970)
Soder-
zhanie
vitaminov
v
novykh
silosnykh
rasteniyakh,
vyrashchivaemykh
v
Komi
ASSR.
[Vitamin
content
of
new
silage
plants
grown
in
the
Komi
ASSR].
5th
Symposium
on
New
Silage
Plants,
Lengingrad,
Part
I,
49.
MOISEEV,
K.
A.;
VOTINOVA,
T.
I.
(1970)
K
voprosu
kariosistematicheskogo
izucheniya
nekotorykh
vidov
silosnykh
rastenli
[A
karyological
study
of
some
species
of
silage
plants]
.
5th
Symposium
on
New
Silage
Plants,
Leningrad,
Part
I,
30-31.
MYAZHUEV,
A.
G.;
LAPKOVSKAYA,
M.
A.
(1972)
Paravnal'naya
praduktsy'nasts'
karmavykh
kul'tur
na
dzyarnova-padzolistykh
syarednesuglinistykh
glebakh
[Comparative
productivity
of
fodder
crops
on
demo-
podzolic
loamy
soils].
Vestsi
A
kademii
Navuk
Belaruskai
SSR.
Seryya
Sel'skagaspadarchykh
Navuk,
1972(2)
3741.
NEW
SOUTH
WALES
DEPARTMENT
OF
AGRICULTURE
(1959)
Russian
comfrey.
Annual
Report
1959,
36.
NORTH
OF
SCOTLAND
COLLEGE
OF
AGRICULTURE
(1978)
Yield
and
chemical
composition
of
Russian
comfrey
grown
alone
and
with
grass.
Research
Investi-
gations
and
Field
Trials
1976-77,
98-99.
PARK,
S.
H.;
CHEE,
S.
H.;
LEE,
J.
W.;
HAN,
I.
K.
(1969)
[Digestibility
of
domestic
feedstuffs
determined
in
vitro]
.
Research
Reports
Office
of
Rural
Develop-
ment,
Suwon,
12(4),
3741.
PATEL,
B.
M.;
PATEL,
P.
S.;
SHUKLA,
P.
C.
(1962)
Nutritive
value
of
neem
leaves,
mangolds
and
comfrey.
Indian
Journal
of
Dairy
Science,
15,
139-145.
PERRING,
F.
(1969)
Symphytum
survey.
Proceedings
of
the
Botanical
Society
of
the
British
Isles,
7,
553-556.
POPESCU,
I.
I.;
P1TI$.
S.;
CASANOVA,
L.
(1971)
Studiul
unor
insusiri
furajere
la
tifineasi
(Symphytum
officinale)
[Study
of
some
fodder
features
of
comfrey
(Symphytum
officinale)].
Anale
Universitatea
Craiova,
dila
(Biologie
kytiinte
Agricole),
3,
274-251.
RAMAN,
I.
A.
(1970)
Biokhimicheskaya
i
zootekhni-
cheskaya
otsenlca
silosov
iz
okopnika,
botvy
gibridnoi
bryukvy
i
topinambura
[Biochemical
and
zootechnical
evaluation
of
silage
from
comfrey,
the
tops
of
hybrid
swedes
and
Jerusalem
artichoke].
5th
Symposium
on
New
Silage
Plants,
Leningrad,
Part
I,
55-56.
ROBERTSON,
R.
W.
(1959)
Russian
(Quaker)
comfrey,
Symphytum
peregrinum.
Forage
Notes,
5(1),
32-33.
SAUNDERS,
P.
J.
C.
(1977)
An
investigation
into
the
potential
of
both
Russian
comfrey
and
a
mixture
of
comfrey
and
perennial
rye-grass
as
a
fodder
crop.
BSc
Thesis,
Department
of
Agriculture,
University
of
Aberdeen,
UK.
SHCHEREVA,
R.;
POPOV,
I.;
PETKOV,
V.;
KAMISHEV,
N.
(1965)
Nyakoi
prouchvaniya
vyrkhu
novata furazhna
kultura
Symphytum
peregrinum
Ldb.
[Certain
investi-
gations
into
a
new
fodder
crop,
Symphytum
peregrinum
Lclb.]
.
Rastenie
vdni
Nauki,
2(6)
113-118.
STAHLIN,
A.
(1964)
Neuere
Futterpflanzen
in
der
Deutschen
Futterproduktion
[Recent
fodder
plants
in
German
fodder
production]
.
Maataloustieteellinen
Aikakauskirja,
36,
22-37.
'
STRANGE,
R.
(1959)
A
comparison
between
Russian
comfrey
and
lucerne.
East
African
Agricultural
Journal,
24,
203-205.
TABIN,
S.;
BERBEC,
S.
(1968)
Wplyw
wapnia
pr2y
zrOznicowanei
wilgotnoici
gleby
na
plonowanie
i
jakoie
zielonki
iywokostu
pastewnego
(Symphytum
peregrinum)
[Influence
of
calcium
at
different
soil
humidity
levels
on
the
yield
and
quality
of
green
herbage
of
fodder
comfrey
(Symphytum
peregrinum)].
Annaks
Universitatis
Mariae
Curie-Sklodowska,
Sectio
E,
23,
301-321.
TABIN,
S.;
BERBEC,
S.;
BOBRZYNSKI,
T.
(1973)
Plono-
wanie
kilku
ekotypeow
tywokostu
lekarskiego
(Symphytum
officinale
L.)
[The
yields
of
some
ecotypes
of
comfrey
(Symphytum
officinale
L.)]
.
Hodowla
Roilin,
Aklimatyzacja
i
Nasiennictwo,
17,
505-511.
TABIN,
S.;
BERBEC,
S.;
WUBIAKOWSKI,
H.
(1966)
Wplyw
poglOwnego
nawozenia
azotowego
na
plony
i
jakosc
fywokostu
(Symphytum
peregrinum)
[Influence
of
nitrogen
top
dressing
on
the
yield
and
quality
of
comfrey
(Symphytum
peregrinum)]
.
Annales
Universitatis
Mariae
Curie-Skfbdowska,
Sectio
E.
21,
139-153.
TANFIL'EV,
V.
G.
(1975)
[Longevity
of
grasses,
legumes
and
some
other
species].
Trudy
Stavropol'skii
Institut
cel'skogo
Khozyaistva,
17,
196-204.
TASCENCO,
V.;
ISAR,
O.;
FEREDEAN,
I.
(1974)
Valoarea
-
nutritivil
a
unor
nutreturi
fibrase
si
radacinose
de
mare
productivitate
cultivate
in
conditii
de
irigare
si
ingrasare
a
soluhu
[Nutntive
value
of
,
high-yield
fibrous
and
root
crops
grown
in
irrigated
and
fertilised
soil].
Lucrbrile
Stiintifice
ale
Institutului
de
Cercetari
Pentru
Nutritia
Antmalelor,
3,
411422.
TUTIN,
T.
G.
(1956)
The
genus
Symphytum
in
Britain.
Watsonia,
3,
280-281.
UK
MINISTRY
OF
AGRICULTURE,
FISHERIES
AND
FOOD
(1975)
Energy
allowances
and
feeding
systems
for
ruminants
Technical
Bulletin,
33.
VAN
DER
ZWEERDE,
H.
(1965)
[Report
on
a
trial
with
Russian
comfrey
in
1953-60].
Verslag
Instituut
voor
Biologisch
en
Scheikundig
Onderzoek
van
Landbouw-
gewassen,
35.
VAN
RENSBURG,
H.
J.
(1958)
Pasture
research.
Annual
Report,
Veterinary
Department,
Tanganyika
1956,
Vol.
2,
20-26.
VAVILOV,
P.
P.;
DOTSENKO,
A.
I.;
DOTSENKO,
R.
A.
(1974)
[Effect
of
age
and
weather
conditions
on
productivity
of
perennial
silage
plants].
Biologicheskie
Osnovy
Povyzheniya
Urozhainosti
Sel'skokhozyaist-
vennykh
KuPtir,
Moscow,
Part
II,
5-9.
VAVILOV,
P.
P.;
F
I
DEL'SHTEIN,
M.
M.;
SOLOV'EVA,
I.
V.
(1973)
Fraktsionnii
sostav
belka
zelenoi
massy
novykh
silosnykh
kul'tur
[Fractional
composition
of
protein
in
green
herbage
of
new
silage
crops].
lzvestiya
Timiryazevskoi
Sel'skokhozyaistvennoi
A
kademii,
1973(5),
84-93.
VAVILOV,
P.
P;
KONDRAT'EV,
A. A.
(1975)
None
kormovye
kul'tury
[New
fodder
crops].
Moscow,
USSR.
VOELCKER,
A.
(1871)
On
the
composition
and
nutritive
value
of
the
prickly
comfrey
(Symphytum
asperrimum).
Journal
of
the
Royal
Agricultural
Society
of
England,
2nd
Series,
7,
387-389.
WADE,
A.
E.
(1958)
The
history
of
Symphytum
asperum
Lepech.
and
S.
X
uplandicum
Nyman
in
Britain.
Watsonia,
4,
117-118.
WATSON,
S.
J.;
NASH,
M.
J.
(1960)
The
conservation
of
grass
and
forage
crops.
2nd
Edition.
Edinburgh,
UK:
Oliver
and
Boyd.
WEMYSS,
D.
W.
(1882)
The
cultivation
of
prickly
comfrey
and
its
use
as
a
fodder
plant.
Transactions
of
the
Highland
and
Agricultural
Society
of
Scotland,
4th
Series,
14,
264-267.
WILLEY,
L.
A.;
KNIGHT,
R.
L
(1962)
Russian
comfrey.
Journal
of
the
National
Institute
of
Agricultural
Botany,
9,
139-144.
WILSON,
D.
B.
(1961a)
Grazing
preferences
of
Hereford
steers.
Forage
Notes,
7(3),
41.
WILSON,
D.
B.
(1961b)
Russian
comfrey
in
southern
Alberta.
Forage
Notes,
7(1),
38-39.
WILSON,
M.;
HENDERSON,
D.
M.
(1966)
British
rust
fungi.
Cambridge,
UK:
Cambridge
University
Press.
WOODMAN,
H.
E.
(1957)
Rations
for
livestock.
Bulletin
Ministry
of
Agriculture,
Fisheries
and
Food,
48
(14th
Edition).
YARTIEV,
A.
G.
(1975)
[Effect
of
weather
conditions
on
dates
for
the
occurrence
of
phenological
phases
in
perennial
silage
plants].
Sezonnoe
Razvitie
Prirody,
1975,
4447.
©
Commonwealth
Agricultural
Bureaux