Contents
lists
available
at
European
Journal
of
Agronomy
j
o u r n a
l
h o
m e
p a g e :
w w w . e l s e v i e r . c o m / l o c a t e / e j a
Nitrogen
fertilizer
replacement
value
of
undigested
liquid
cattle
manure
and
digestates
Daniele
Cavalli
,
Giovanni
Cabassi
,
Lamberto
Borrelli
,
Gabriele
Geromel
,
Luca
Bechini
,
Luigi
Degano
,
Pietro
Marino
Gallina
a
Dipartimento
di
Scienze
Agrarie
e
Ambientali—Produzione,
Territorio,
Agroenergia,
Università
degli
Studi
di
Milano,
Milano,
Italy
b
Consiglio
per
la
ricerca
in
agricoltura
e
l’analisi
dell’economia
agraria
(CREA–FLC),
Lodi,
Italy
a
r
t
i
c
l
e
i
n
f
o
Article
history:
Received
24
February
2015
Received
in
revised
form
13
October
2015
Accepted
21
October
2015
Available
online
11
November
2015
Keywords:
Apparent
nitrogen
recovery
Mineral
fertilizer
equivalency
Residual
nitrogen
effects
Animal
slurry
Anaerobic
digestion
Liquid
fraction
Solid
fraction
Catch
crop
a
b
s
t
r
a
c
t
Accurate
estimation
of
animal
manure
nitrogen
(N)
availability
is
required
to
maximize
crop
N
use
effi-
ciency
and
reduce
environmental
N
losses.
Many
field
and
laboratory
experiments
have
shown
that
first-year
net
mineralization
of
manure
organic
N
is
often
negligible,
which
often
causes
crop
available
N
to
approximate
the
ammonium
N
content
of
the
manure.
Anaerobic
digestion
increases
the
ammonium
share
and
reduces
the
C
to
organic
N
ratio
of
animal
manures,
potentially
increasing
their
N
fertilizer
value.
In
2011,
we
undertook
a
three-year
field
experiment
in
Northern
Italy
to
estimate
the
N
fertilizer
value
of
four
manures:
undigested
cattle
slurry,
digested
cattle
slurry-maize
mix,
and
liquid
and
solid
fractions
of
the
digested
slurry-maize
mix.
The
experiment
also
allowed
us
to
test
if
ammonium
recovery
was
similar
among
manures,
and
between
manures
and
ammonium
sulphate.
Fertilizers
were
applied
annually
to
plots
before
silage
maize
cultivation
that
was
followed
by
an
unfertilized
Italian
ryegrass
crop.
Results
showed
that
the
recovery
of
ammonium
from
manure
in
maize
did
not
differ
significantly
compared
to
ammonium
sulphate
among
all
the
fertilizers
in
2013;
however,
in
2011
and
2012
it
was
significantly
lower
for
all
manures
except
digested
slurry-maize
mix
and
its
liquid
fraction
in
2011.
The
increased
recovery
of
applied
N
in
2012
and
2013
for
solid
fraction
and
undigested
manure
were
likely
due
to
the
residual
effect
of
previously
applied
organic
N.
©
2015
Elsevier
B.V.
All
rights
reserved.
1.
Introduction
The
efficiency
of
plants
to
take
up
nitrogen
(N)
from
undigested
manures
and
anaerobic
digestion
by-products
(digestates)
is
usu-
ally
assessed
through
apparent
N
recovery
(ANR)
and
N
fertilizer
replacement
value
(NFRV)
calculations.
The
ANR
represents
the
fraction
of
applied
total
N
that
can
be
taken
up
by
the
crop
in
addition
to
what
is
taken
up
by
an
unfertilized
control
in
a
single
season
after
fertilizer
application.
NFRV
–
also
known
as
the
mineral
fertilizer
equivalency
–
equals
the
organic
fertilizer
ANR
divided
by
the
mineral
fertilizer
ANR
Both
indices
can
also
be
calculated
for
ammonium-N
(NH
4
-N)
provided
by
different
manures.
Many
laboratory
incubations
and
field
∗ Corresponding
author.
Fax:
+39
0250316575.
address:
(D.
Cavalli).
experiments
involving
untreated
(
digested
manures
(
shown
that
first-year
crop
available
N
often
approximates
the
NH
4
-
N
content
of
manure
and
thus
NFRV
approximately
equals
the
manure
NH
4
-N
to
total
N
ratio.
The
relevance
of
the
contribution
of
manure
organic
N
to
plant
nutrition
becomes
more
important
when
manure
is
applied
repeat-
edly
to
the
soil
during
consecutive
years.
In
such
cases,
the
slow
mineralization
of
previously
applied
organic
N,
and
the
remineral-
ization
of
immobilized
manure
NH
4
-N,
can
substantially
increase
the
NFRV
of
manures
during
subsequent
years
Digestates
typically
have
high
NH
4
-N
to
total
N
ratios
that
raise
their
potential
N
availability
for
crops
Nowadays,
digestates
often
consist
of
animal
manures
co-digested
with
other
biomasses
used
to
increase
http://dx.doi.org/10.1016/j.eja.2015.10.007
1161-0301/©
2015
Elsevier
B.V.
All
rights
reserved.
D.
Cavalli
et
al.
/
Europ.
J.
Agronomy
73
(2016)
34–41
35
methane
production
(
Moreover,
to
facil-
itate
the
fertilizer
use
of
both
digested
and
raw
manures,
their
liquid
and
solid
fractions
are
separated
(
In
fact,
separation
makes
export
of
the
solid
fraction
off
the
farm
easy,
which
permits
an
efficient
strategy
to
reduce
N
and
phosphorus
loads
per
unit
of
land
area
where
it
is
high.
Both
co-digestion
and
solid–liquid
sep-
aration
can
influence
digestate
N
availability
for
crops
(
Experiments
that
evaluate
the
NFRVs
of
unseparated
digested
and
co-digested
manures
and
their
solid
or
liquid
fractions
are
still
scarce
further
research
is
needed
to
better
assess
their
N
supply
for
crop,
as
well
as
across
years.
To
this
end,
we
established
a
field
experiment
in
2011
(
measure
the
NFRV
of
undigested
and
digested
cattle
manure
named
SINBION-field,
in
which
silage
maize
was
fertilized
with
ammonium
sulphate
(AS),
untreated
cattle
slurry
(US),
unsep-
arated
digestate
from
a
mix
of
cattle
slurry
and
maize
(DSMM),
and
the
liquid
(LF)
and
solid
(SF)
fractions
of
DSMM.
In
this
experiment
we
measured
ANR
and
NFRV
of
the
applied
manures
and
tested
several
hypotheses
regarding
the
effects
during
the
first
year
after
their
application:
i)
applied
NH
4
-N
recovery
is
similar
among
manures;
ii)
applied
NH
4
-N
recovery
is
similar
for
manures
and
AS;
iii)
first-year
NFRV
of
manures
can
be
approximated
by
their
NH
4
-
N
to
total
N
ratio
(i.e.,
most
manure
ammonium
is
available
in
the
first
year
after
application;
part
of
the
inevitable
N
loss
is
compensated
for
by
mineralized
N
from
the
easily
decompos-
able
N
fraction
of
the
manure).
that
ammonium
applied
to
the
soil
with
US,
SF,
and
LF
was
less
available
for
maize
than
that
of
AS.
They
also
observed
that
recovery
of
applied
N
with
SF
and
US
increased
in
the
second
year,
suggesting
that
N
residual
effects
contributed
to
maize
N
uptake.
Herein
we
report
the
third-year
results
of
data
with
in-season
measurements
of
maize
biomass,
maize
N
uptake,
and
soil
mineral
N.
Our
aims
are:
to
enhance
the
understanding
of
N
dynamics
in
a
soil-crop
system,
and
to
discuss
the
cumulative
effects
of
repeated
treatments.
2.
Material
and
methods
2.1.
Experimental
site
and
design
The
three-year
field
experiment
started
in
spring
2011
on
a
flat
area
located
in
Montanaso
Lombardo
(Lodi),
Italy
(45
◦
20
32
N,
9
◦
26
43
E,
altitude
80
m
asl).
The
field
had
been
cultivated
with
bar-
ley
(Hordeum
vulgare
L.)
and
silage
maize
(Zea
mays
L.)
prior
to
the
start
of
the
experiment.
No
organic
fertilizers
had
been
applied
in
the
previous
ten
years.
The
0–30
cm
soil
profile
of
the
field
displayed
the
following
characteristics:
sand,
469
g
kg
−1
,
silt,
394
g
kg
−1
,
clay,
137
g
kg
−1
;
pH
(H
2
O)
of
5.8;
total
N,
1.01
and
organic
C,
8.44
(both
g
kg
−1
);
extractable
P,
61
mg
kg
−1
per
Bray
and
Kurtz
method;
exchange-
able
K,
167
mg
kg
−1
;
bulk
density,
1.49
t
m
−3
.
The
climate
of
the
area
(average
1993–2010)
is
characterized
by
an
annual
rainfall
of
875
mm
and
an
average
annual
mean
air
temperature
of
13.4
◦
C
(
In
spring
2011,
an
experiment
was
established
in
plots
of
112
m
2
arranged
in
a
randomized
block
design
with
four
replicates,
and
involving
six
treatments:
an
unfertilized
control
(CON),
ammonium
sulphate
(AS)
and
four
manure
varieties
Every
year,
at
no
more
than
a
week
before
spreading,
the
manures
were
sampled
to
determine
the
correct
application
rate.
To
ensure
that
NH
4
-N
recovery
across
treatments
could
be
com-
pared
later,
the
application
rate
was
calculated
to
deliver
the
same
amount
of
NH
4
-N
to
all
fertilized
treatments.
Furthermore,
the
amount
of
NH
4
-N
distributed
to
all
treatments
was
set
equal
to
that
supplied
by
US
when
applied
at
340
kg
N
ha
−1
.
Effective
NH
4
-
N
application
rates
deviated
from
intended
rates
(represented
by
those
of
AS
in
because
estimated
manure-N
concen-
trations
at
the
preliminary
sampling
and
at
the
time
of
spreading
were
not
equal.
The
CON
and
AS
plots
received
triple
super-
phosphate
(40
kg
P
ha
−1
)
and
potassium
chloride
(230
kg
K
ha
−1
)
fertilizers
before
sowing.
On
31
May
2011,
DSMM,
LF,
and
US
were
Table
2
Total
N
and
NH
4
-N
(kg
N
ha
−1
)
applied
before
maize
sowing
in
2011–2013
with
ammonium
sulphate
and
manures.
Year
Treatment
AS
DSMM
LF
SF
US
Total
N
2011
159
264
218
643
200
2012
152
306
291
606
271
2013
131
250
213
703
214
NH
4
-N
2011
159
120
111
151
106
2012
152
142
147
226
136
2013
131
125
109
190
111
a
AS:
ammonium
sulphate;
DSMM:
unseparated
digestate
from
a
mix
of
cattle
slurry
and
maize;
LF:
liquid
fraction
of
DSMM;
SF:
solid
fraction
of
DSMM;
US:
untreated
cattle
slurry.
Table
1
Chemical–physical
characteristics
of
the
manures
used
in
the
field
experiment
(average
±
standard
deviation).
Manure
Year
pH
(water)
Organic
C
Total
N
NH
4
-N
Organic
C/organic
N
NH
4
-N/total
N
(g
kg
−1
)
(g
kg
−1
DM)
DSMM
2011
65.1
8.0
±
0.0
395.8
±
5.8
55.9
±
0.3
25.5
±
0.3
13.0
45.6
2012
61.3
8.2
±
0.0
389.4
±
0.3
61.3
±
0.3
28.6
±
0.1
11.9
46.6
2013
57.8
8.1
±
0.0
368.7
±
0.2
64.2
±
0.2
32.0
±
0.2
11.5
49.9
LF
2011
47.9
8.0
±
0.0
363.6
±
2.2
67.0
±
0.1
34.2
±
0.0
11.1
51.1
2012
53.6
7.9
±
0.0
383.6
±
4.3
65.2
±
0.0
32.9
±
0.1
11.9
50.5
2013
40.8
8.3
±
0.0
357.4
±
1.9
67.0
±
0.0
34.3
±
0.5
10.9
51.3
SF
2011
256.5
9.6
±
0.0
439.8
±
5.5
21.9
±
0.2
5.1
±
0.0
26.2
23.4
2012
296.3
9.0
±
0.2
436.7
±
4.5
20.9
±
0.4
7.8
±
0.3
33.3
37.3
2013
276.0
9.8
±
0.1
431.6
±
5.2
22.9
±
0.9
6.2
±
0.3
25.8
27.0
US
2011
82.3
7.3
±
0.0
436.4
±
1.3
39.2
±
0.2
20.8
±
0.2
23.7
53.0
2012
84.2
7.3
±
0.0
427.7
±
5.8
43.1
±
0.3
21.7
±
0.1
20.0
50.4
2013
37.5
7.9
±
0.0
407.0
±
0.6
57.4
±
0.1
29.7
±
0.2
14.7
51.8
a
DSMM:
unseparated
digestate
from
a
mix
of
cattle
slurry
and
maize;
LF:
liquid
fraction
of
DSMM;
SF:
solid
fraction
of
DSMM;
US:
untreated
cattle
slurry.
b
Dry
matter,
single
determination.
36
D.
Cavalli
et
al.
/
Europ.
J.
Agronomy
73
(2016)
34–41
2011
2012
0
25
50
75
100
125
150
175
200
225
250
-10
-5
0
5
10
15
20
25
30
J
F
M
A
M
J
J
A
S
O
N
D
Pre
ci
p
it
a
tion
(mm
)
M
ean
air
tem
perat
u
re
(°
C
)
Mon
ths and
da
ys
0
25
50
75
100
125
150
175
200
225
250
-10
-5
0
5
10
15
20
25
30
J
F
M
A
M
J
J
A
S
O
N
D
P
reci
p
it
a
tion
(mm
)
M
ean
a
ir
tem
perat
u
re
(
°C)
Mon
ths and
da
ys
2013
2014
0
25
50
75
100
125
150
175
200
225
250
-10
-5
0
5
10
15
20
25
30
J
F
M
A
M
J
J
A
S
O
N
D
P
reci
p
it
a
tion
(mm)
M
ean
ai
r
te
m
perat
u
re
(
°C)
Mon
ths and
da
ys
0
25
50
75
100
125
150
175
200
225
250
-10
-5
0
5
10
15
20
25
30
J
F
M
A
M
J
J
A
S
O
N
D
P
reci
p
it
a
tion
(mm)
M
ean
ai
r
te
m
perat
u
re
(
°C)
Mon
ths and
da
ys
Air t
empera
ture 2011-2014
Air t
empera
ture 1993-2010
Preci
pitati
ons
2011-2
014
Preci
pitati
ons
1993-2
010
Fig.
1.
Daily
mean
air
temperature
and
accumulated
monthly
precipitation
in
Montanaso
Lombardo
(Italy).
Vertical
grey
bars
represent
fertilizer
spreading
and
maize
harvest
days.
applied
using
a
trailing
hose
spreader
and
were
incorporated
within
minutes
into
the
soil
with
a
rotary
harrow
(depth
10
cm).
On
17
May
2012
and
12
June
2013,
liquid
slurries
were
injected
to
a
depth
of
15
cm
using
a
Xerion
3800
Saddle
Trac
(Claas,
Harsewinkel,
Germany)
equipped
with
a
15
m
3
SGT
tanker
and
injector
system
TILL-R8
(Mainardi,
Cremona,
Italy)
composed
of
eight
elements
located
70
cm
distance
from
each
other.
On
the
same
dates,
chem-
ical
fertilizers
and
SF
were
hand
spread
and
incorporated
into
the
soil
with
a
rotary
harrow
within
minutes.
The
day
after
fertilization,
the
field
was
ploughed
to
30
cm,
har-
rowed,
and
sown
with
maize
within
three
days
(Hybrid
PR33M15,
Pioneer
Hi-Bred
Italia
S.r.l.)
at
a
between-row
distance
of
70
cm
and
a
planting
density
of
7.1
plants
m
−2
.
The
field
was
surface-irrigated
according
to
irrigation
water
availability
and
precipitations.
The
whole
maize
plants
were
harvested
for
silage
on
the
following
dates:
13
September
2011,
30
August
2012,
and
3
October
2013.
Within
two
weeks
post
maize
harvest,
the
field
was
sown
with
Italian
ryegrass
(Lolium
multiflorum
Lam.,
cultivar
Asso)
without
additional
fertilizer
applications.
The
stand
of
Italian
ryegrass
grew
until
it
was
harvested
on
10
May
2012,
23
May
2013,
and
14
May
2014.
2.2.
Manure
collection
and
analysis
The
DSMM
came
from
a
biogas
plant
and
was
a
mix
of
cattle
slurry
co-digested
with
silage
maize
(about
30%
on
a
fresh
matter
basis)
and
beet
pulp
or
tomato
peels
(about
1%
on
a
fresh
matter
basis).
The
liquid
and
solid
fractions
(LF
and
SF)
of
DSMM
were
obtained
after
screw
press
mechanical
separation.
The
US
was
col-
lected
from
a
second
farm
where
the
storage
tank
lay
beneath
the
litter-free,
gridded
stable
floor.
Dry
matter
(DM)
content,
organic
C,
total
N,
and
NH
4
-N
concentration
of
the
manures
were
determined
per
are
reported
in
fatty
acids
(VFA)
were
determined
by
HPLC
(
steam
dis-
tillation
according
to
procedure
DIN
38414–19
(1999)
Ash
content
was
measured
after
incineration
in
a
muffle
at
550
◦
C
Ash-free
neutral
detergent
fiber
(NDF),
acid
detergent
fiber
(ADF),
and
acid
detergent
lignin
(ADL)
were
all
determined
in
dried
samples
ground
to
pass
1
mm
screen
accord-
ing
to
the
procedures
of
using
an
Ankom
200
fiber
analyzer
(Ankom
Technology
Corp.,
Fairport,
NY).
Hemicellulose
was
calcu-
lated
as
the
difference
between
NDF
and
ADF,
while
cellulose
was
calculated
as
the
difference
between
ADF
and
ADL.
Soluble
organic
matter
was
figured
as
the
DM
not
recovered
in
ash,
VFA
and
NDF
fractions
(
2.3.
Above
ground
biomass
sampling
and
analysis
Above
ground
biomass
(AGB)
of
maize
was
sampled
at
the
following
phenological
stages
V3,
V6,
V9,
flowering
(R1),
and
dent
maturity
(R5
harvest
stage
for
silage
pro-
duction).
The
AGB
of
Italian
ryegrass
was
sampled
at
harvest
when
it
was
completely
removed
from
the
field.
Crop
sampling
was
done
D.
Cavalli
et
al.
/
Europ.
J.
Agronomy
73
(2016)
34–41
37
0
10
20
30
40
50
60
70
80
90
100
110
DSMM
LF
SF
US
%
D
ry
ma
tter
Soluble
matter
Volatile f
atty acids
Hemicellulose
Cellulose
Lignin
Ash
Fig.
2.
Dry
matter
fractions
of
the
applied
manures.
The
soluble
fraction
was
esti-
mated
as
DM
unaccounted
for
in
the
other
fractions
(average
±
standard
deviation).
DSMM:
unseparated
digestate
from
a
mix
of
cattle
slurry
and
maize;
LF:
liquid
fraction
of
DSMM;
SF:
solid
fraction
of
DSMM;
US:
untreated
cattle
slurry.
according
to
the
exception
of
harvests
at
V3-R1
when
15
instead
of
40
plants
plot
−1
were
sampled.
Each
year,
maize
plant
density
was
measured
in
each
plot
at
V6;
the
average
value
for
the
three
years
was
6.9
±
0.3
plants
m
−2
.
2.4.
Soil
sampling
and
analysis
Soil
samples
(0–30
cm
layer)
were
collected
from
each
plot
before
fertilization
(year
2011)
and
at
each
date
when
AGB
was
estimated;
additional
samples
from
the
30–60
cm
profile
were
collected
after
maize
harvest
(3
October
2013)
and
after
Italian
rye-
grass
harvest
(14
May
2014).
Methods
of
soil
sampling
and
analysis
are
reported
in
2.5.
Calculations
and
statistical
analyses
Subtracting
maize
(or
Italian
ryegrass)
N
uptake
in
CON
from
maize
(or
Italian
ryegrass)
N
uptake
in
the
fertilized
treatment
–
separately
for
each
experimental
block
–
and
dividing
the
result
by
the
N
applied
results
in
an
apparent
N
recovery
value
(ANR).
This
calculation
was
done
considering
as
the
denominator
either
the
total
N
or
the
NH
4
-N
applied
to
obtain
ANR
and
ANR
NH4-N
,
respec-
tively.
Both
indices
were
calculated
for
season
one
(2011–2012),
two
(2012–2013),
and
three
(2013–2014).
An
analysis
of
variance
(ANOVA)
was
performed
separately
for
each
year,
crop,
and
sampling
date
using
the
SPSS
procedure
UNI-
ANOVA
(SPSS
Version
22.0.0).
Mean
separation
was
conducted
with
the
HSD
Tukey
test
(P
<
0.05).
The
treatment
was
considered
a
fixed
factor,
while
the
block
was
random.
The
homogeneity
of
variances
was
evaluated
using
the
Levene
test
(P
<
0.05).
Within
the
text,
sig-
nificant
effects
of
fertilizer
application
are
reported
when
the
P
value
is
below
0.05.
3.
Results
3.1.
Above
ground
biomass
and
nitrogen
uptake
In
2012
and
2013,
as
opposed
to
2011,
AS
and
manure
appli-
cations
significantly
increased
maize
AGB
compared
to
CON
on
most
dates
from
V3
to
flowering
Maize
AGB
differences
among
fertilized
treatments
occurred
at
harvest
in
2011
(US
<AS
and
DSMM)
and
2012
(US,
SF,
and
LF
were
lower
than
AS),
but
dis-
appeared
completely
in
2013.
During
the
three
years
no
significant
differences
were
found
for
the
AGB
of
Italian
ryegrass
among
AS,
0
1
2
3
4
5
6
7
0
5
10
15
20
25
)
M
D
%(
t
n
et
n
o
c
N
s
s
a
m
oi
b
d
u
or
g
e
v
o
b
A
Aboveground
biomass (t DM ha
-1
)
CON
AS
DSMM
LF
SF
US
%N max
%N critical
%N
min
Fig.
3.
Nitrogen
concentration
in
above
ground
maize
biomass
versus
above
ground
biomass
in
Montanaso
Lombardo
(Italy)
over
three
years
with
five
sampling
dates
per
year.
CON:
unfertilized
soil;
AS:
ammonium
sulphate;
DSMM:
unseparated
digestate
from
a
mix
of
cattle
slurry
and
maize;
LF:
liquid
fraction
of
DSMM;
SF:
solid
fraction
of
DSMM;
US:
untreated
cattle
slurry.
Nmax,
Ncritical,
and
Nmin
are
the
three
N
dilution
curves
proposed
for
maize
by
DSMM,
LF,
or
US;
on
the
contrary,
application
of
SF
enhanced
Italian
ryegrass
AGB
compared
to
AS
and
the
other
manures
(
Maize
N
uptake
(
followed
a
similar
trend
to
that
of
AGB.
In
2012
and
2013,
N
uptake
in
fertilized
treatments
was
significantly
higher
than
CON
on
all
sampling
dates
with
few
exceptions.
As
observed
for
AGB
at
maize
harvest
in
2013,
differ-
ences
in
N
uptake
between
AS
and
manures,
and
among
manures,
disappeared.
Application
of
SF
increased
(although
not
always
significantly)
N
uptake
of
Italian
ryegrass
compared
to
other
treat-
ments
in
all
three
growing
seasons
the
relationship
between
maize
AGB
and
its
N
con-
centration,
as
well
as
critical,
minimum,
and
maximum
N
dilution
curves
(
Most
treatments
were
already
N
deficient
from
the
first
stages
of
plant
growth,
as
indicated
by
the
dots
beneath
the
critical
N
curve.
Only
AS
and
DSMM
were
fre-
quently
found
above
the
critical
curve
until
R1,
after
which
these
treatments
were
slightly
N-limited
at
crop
harvest.
3.2.
Apparent
nitrogen
recovery
and
nitrogen
fertilizer
replacement
value
Across
the
three
years,
ANR
in
maize
was
significantly
higher
in
AS
(68–82%)
compared
to
manure-fertilized
treatments,
with
the
exception
of
LF
in
2013
(
In
the
2013–2014
season,
ANR
from
LF
in
maize
was
34%
higher
than
that
in
the
treatment
with
the
lowest
ANR
value
(SF),
while
ANR
in
Italian
ryegrass
did
not
differ
among
treatments
(on
average
4%).
In
the
same
growing
sea-
son,
on
average
ANR
NH4-N
in
maize
was
77%,
without
significant
differences
among
treatments,
while
ANR
NH4-N
in
Italian
ryegrass
was
significantly
higher
in
SF
compared
to
AS
(+11%).
Opposed
to
AS
and
DSMM
that
showed
an
almost
constant
ANR
and
ANR
NH4-N
across
years,
the
trend
of
ANR
and
ANR
NH4-N
in
maize
for
SF
and
US
increased
consistently
from
the
first
to
second
growing
season;
for
these
two
treatments
the
results
for
the
third
growing
season
were
similar
to
the
second
one.
Similar
to
observations
of
ANR
NH4-N
,
in
2013
there
were
no
sig-
nificant
differences
in
NFRV
NH4-N
among
the
treatments
(
In
the
same
year,
NFRV
was
still
higher
in
LF
compared
to
SF.
38
D.
Cavalli
et
al.
/
Europ.
J.
Agronomy
73
(2016)
34–41
Table
3
Above
ground
dry
matter
of
maize
and
Italian
ryegrass
(t
DM
ha
−1
)
as
a
result
of
fertilization
during
three
growing
seasons
at
Montanaso
Lombardo
(Italy).
Letters
indicate
significant
differences
among
treatments
within
year
and
sampling
date
(P
<
0.05)
(HSD
Tukey
test).
Season
Crop
development
stage
Date
Treatment
CON
AS
DSMM
LF
SF
US
2011–2012
Maize
V3
06/20/2011
0.04a
0.04a
0.03a
0.04a
0.04a
0.03a
Maize
V6
06/29/2011
0.3ab
0.3b
0.3ab
0.3ab
0.2ab
0.2a
Maize
V9
07/12/2011
2.5a
2.8a
2.3a
2.4a
2.7a
2.1a
Maize
R1
08/06/2011
10.7a
11.7a
9.4a
10.1a
10.6a
9.0a
Maize
R5
09/13/2011
18.6ab
22.3b
22.3b
19.9ab
17.8ab
16.5a
Italian
ryegrass
harvest
05/10/2012
5.6a
7.1b
7.2b
7.0b
8.6c
6.6ab
2012–2013
Maize
V3
06/08/2012
0.03a
0.05b
0.06b
0.05b
0.05b
0.05b
Maize
V6
06/18/2012
0.4a
0.7b
0.9b
0.8b
0.7b
0.8b
Maize
V9
07/02/2012
2.0a
5.1c
4.4bc
4.3bc
3.8b
3.9b
Maize
R1
05/25/2012
6.1a
14.0c
12.0bc
10.6b
10.4b
10.6b
Maize
R5
08/30/2012
12.3a
24.1e
22.9de
20.0bc
21.2cd
19.1b
Italian
ryegrass
harvest
05/23/2013
3.3a
3.8a
4.2a
4.5ab
5.5b
4.2a
2013–2014
Maize
V3
07/01/2013
0.01a
0.01ab
0.02bc
0.02cd
0.03d
0.02cd
Maize
V6
07/15/2013
0.2a
0.3ab
0.4b
0.5bc
0.6c
0.4b
Maize
V9
07/22/2013
0.6a
1.1b
1.3b
1.6c
1.6c
1.1b
Maize
R1
08/13/2013
5.7a
10.1bc
10.4bc
11.3c
11.1c
7.9ab
Maize
R5
10/03/2013
12.0a
19.9b
21.4b
20.8b
21.1b
18.2b
Italian
ryegrass
harvest
05/14/2014
0.8a
1.3ab
1.8ab
2.0ab
3.7c
2.1b
a
V3:
maize
third
leaf;
V6:
maize
sixth
leaf;
V9:
maize
nineth
leaf;
R1:
maize
flowering;
R5:
maize
dent
maturity
(silage
harvest).
b
CON:
unfertilized
soil;
AS:
ammonium
sulphate;
DSMM:
unseparated
digestate
from
a
mix
of
cattle
slurry
and
maize;
LF:
liquid
fraction
of
DSMM;
SF:
solid
fraction
of
DSMM;
US:
untreated
cattle
slurry.
3.3.
Soil
mineral
nitrogen
SMN
dynamics
during
the
maize
growing
season
was
similar
in
all
treatments;
SMN
concentration
increased
from
pre-planting
to
V3
or
V6,
and
then
strongly
decreased
from
V9
onward
until
it
reached
a
rather
low
level
at
maize
harvest
After
maize
harvest
in
September
2012
and
October
2013,
and
Italian
ryegrass
harvest
in
May
2013,
application
of
SF
significantly
increased
post-harvest
SMN
concentration
(in
the
0–30
cm
soil
layer)
compared
to
other
treatments.
4.
Discussion
Our
hypothesis
that
ammonium-N
recovery
is
similar
among
manures
was
not
confirmed
in
2011
when
ANR
NH4-N
of
DSMM
was
significantly
higher
than
that
of
SF
and
US
however,
it
was
confirmed
in
the
other
two
years.
Differences
in
ANR
NH4-N
values
were
observed
between
manures
and
AS
for
LF
in
2012
and
for
SF
and
US
in
2011
and
2012
which
contradicted
our
hypothesis
that
manure
NH
4
-N
is
as
available
as
is
that
of
AS.
Contradiction
of
this
latter
hypothesis
for
SF
and
US
in
2011
and
2012
consequently
makes
false
our
last
hypothesis
that
first-year
NFRV
of
manures
is
similar
to
their
NH
4
-N
to
total
N
ratio.
In
fact,
NFRVs
of
US
and
SF
were
much
lower
than
their
NH
4
-N
to
total
N
ratios.
Conversely,
2013
US
results
were
more
consistent
with
the
hypothesis
of
equal
ANR
NH4-N
values
between
mineral
fertilizers
and
untreated
slurries
found
in
other
field
experiments
even
after
a
single
manure
application
(
Moreover,
the
measured
ANR
NH4-N
of
SF
in
2013
was
con-
Table
4
Above
ground
N
uptake
of
maize
and
Italian
ryegrass
(kg
N
ha
−1
)
as
a
result
of
fertilization
during
three
growing
seasons
at
Montanaso
Lombardo
(Italy).
Letters
indicate
significant
differences
among
treatments
within
year
and
sampling
date
(P
<
0.05)
(HSD
Tukey
test).
Season
Crop
development
stage
Date
Treatment
CON
AS
DSMM
LF
SF
US
2011–2012
Maize
V3
06/20/2011
1.6a
1.7a
1.3a
1.4a
1.3a
1.2a
Maize
V6
06/29/2011
13ab
14b
11ab
11ab
8a
8a
Maize
V9
07/12/2011
55a
83b
57a
66ab
58a
49a
Maize
R1
08/06/2011
100a
177b
110a
146ab
124ab
102a
Maize
R5
09/13/2011
138a
247c
217bc
182ab
146a
131a
Italian
ryegrass
harvest
05/10/2012
42a
64b
60b
58b
78c
52ab
2012–2013
Maize
V3
06/08/2012
0.9a
2.1b
2.8b
2.3b
1.9b
2.3b
Maize
V6
06/18/2012
13a
28b
30b
27b
21b
26b
Maize
V9
07/02/2012
29a
112c
76b
75b
53b
54b
Maize
R1
05/25/2012
42a
179c
102b
99ab
92ab
80ab
Maize
R5
08/30/2012
78a
202e
170cd
152bc
183de
138b
Italian
ryegrass
harvest
05/23/2013
31a
34a
42ab
42ab
56b
40a
2013–2014
Maize
V3
07/01/2013
0.4a
0.6ab
0.7bc
0.9cd
1.2d
0.9cd
Maize
V6
07/15/2013
5a
12ab
13ab
18bc
22c
12ab
Maize
V9
07/22/2013
17a
38bc
38bc
47c
43c
30b
Maize
R1
08/13/2013
67a
172c
151c
165c
141bc
100ab
Maize
R5
10/03/2013
83a
180b
192b
191b
199b
151b
Italian
ryegrass
harvest
05/14/2014
9a
14a
17a
20a
37b
21a
a
V3:
maize
third
leaf;
V6:
maize
sixth
leaf;
V9:
maize
nineth
leaf;
R1:
maize
flowering;
R5:
maize
dent
maturity
(silage
harvest).
b
CON:
unfertilized
soil;
AS:
ammonium
sulphate;
DSMM:
unseparated
digestate
from
a
mix
of
cattle
slurry
and
maize;
LF:
liquid
fraction
of
DSMM;
SF:
solid
fraction
of
DSMM;
US:
untreated
cattle
slurry.
D.
Cavalli
et
al.
/
Europ.
J.
Agronomy
73
(2016)
34–41
39
Sea
son 2011–2012
Season 2012
–2013
Season 2013
–2014
AN
R
(%
ap
pl
ie
d N)
d
c
bc
ab
a
b
ab
ab
a
a
D
C
BC
AB
A
-10
0
10
20
30
40
50
60
70
80
90
100
110
AS
DSMM
LF
SF
US
Itali
an ryeg
rass
Mai
ze
b
a
a
a
a
a
a
a
a
a
B
A
A
A
A
-10
0
10
20
30
40
50
60
70
80
90
100
110
AS
DSMM
LF
SF
US
c
ab
bc
a
ab
a
a
a
a
a
C
AB
BC
A
AB
-10
0
10
20
30
40
50
60
70
80
90
100
110
AS
DSMM
LF
SF
US
AN
R
N
H4
–N
(%
ap
pl
ie
d NH
4
–N
)
c
c
bc
ab
a
ab
ab
ab
b
a
C
C
BC
AB
A
-10
0
10
20
30
40
50
60
70
80
90
100
110
AS
DSMM
LF
SF
US
Italian ryeg
rass
Mai
ze
b
ab
a
a
a
a
ab
ab
b
ab
B
AB
A
A
A
-10
0
10
20
30
40
50
60
70
80
90
100
110
AS
DSMM
LF
SF
US
a
a
a
a
a
a
ab
ab
b
ab
A
A
A
A
A
-10
0
10
20
30
40
50
60
70
80
90
100
110
AS
DSMM
LF
SF
US
Fig.
4.
Apparent
recovery
at
harvest
of
applied
total
N
(ANR)
and
NH
4
-N
(ANR
NH4-N
)
in
maize
and
Italian
ryegrass
(%)
at
Montanaso
Lombardo
(Italy).
AS:
ammonium
sulphate;
DSMM:
unseparated
digestate
from
a
mix
of
cattle
slurry
and
maize;
LF:
liquid
fraction
of
DSMM;
SF:
solid
fraction
of
DSMM;
US:
untreated
cattle
slurry.
Letters
indicate
significant
differences
(P
<
0.05)
among
treatments
within
a
year
(HSD
Tukey
test).
Lowercase
letters
in
bold:
significant
differences
for
maize;
lowercase
letters
in
italic:
significant
differences
for
Italian
ryegrass;
uppercase
letters:
significant
differences
for
maize
plus
Italian
ryegrass.
sistent
with
the
range
reported
for
solid
cattle
manures
(12–63%)
by
Within
this
experiment,
the
N
rate
applied
in
AS
and
manure-
fertilized
treatments
was
expected
to
lie
in
a
linear
responsive
N
domain
(characterized
by
constant
ANR)
that
usually
extends
up
to
200
kg
N
ha
−1
for
silage
maize
culti-
vated
in
the
Po
Plain
in
Northern
Italy.
Thus,
we
anticipated
ANRs
and
NFRVs
not
to
be
substantially
affected
by
applied
NH
4
-N
rates
(at
most
226
kg
ha
−1
for
SF
in
2012)
(
even
considering
residual
N
effects,
N
uptake
in
maize
did
not
exceed
200
kg
ha
−1
in
2012
and
2013
Moreover,
the
AGB
and
its
N
con-
centration
(
suggest
that
all
treatments
were
not
in
luxury
N
consumption,
which
means
that
ANR
and
NFRV
were
at
their
highest
possible
levels
under
the
pedological,
meteorological,
and
cropping
conditions
of
the
experiment.
Therefore,
we
consider
the
NFRVs
measured
in
this
experiment
to
be
of
practical
interest
to
better
define
N
management
plans
in
the
studied
area.
We
suggest
that
the
differences
in
ANRs
and
NFRVs
among
manures
in
the
three
years
were
mainly
due
to
differences
in
C
and
N
turnover
related
to
the
immobilization
of
mineral
N
and
the
mineralization
of
organic
N
in
the
first
and
subsequent
years
after
application,
assuming
negligible
losses
via
ammonia
volatilization
(due
to
incorporation
of
the
manures
within
minutes
after
applica-
tion
and
soil
pH
of
5.8;
emissions
of
N
2
O
and
N
2
.
Indeed,
in
the
AS
treatment,
only
16–21%
of
the
applied
NH
4
-N
was
not
recovered
during
complete
crop
rotation
(
which
suggests
that
substantial
losses
of
N
via
leaching
and
denitrification
did
not
occur.
Leaching
during
maize
growth
was
assumed
to
be
similar
in
all
fertilized
plots.
Year 20
11
Year 20
12
Year 20
13
NFR
V
(%
ap
pl
ie
d N)
b
ab
a
a
-10
0
10
20
30
40
50
60
70
80
90
100
DSMM
LF
SF
US
b
b
a
ab
-10
0
10
20
30
40
50
60
70
80
90
100
DSMM
LF
SF
US
ab
b
a
ab
-10
0
10
20
30
40
50
60
70
80
90
100
DSMM
LF
SF
US
NFR
V
NH
4–N
(%
ap
pl
ie
d NH
4
–N
)
b
ab
a
a
-20
0
20
40
60
80
100
120
140
160
DSMM
LF
SF
US
b
ab
a
a
-20
0
20
40
60
80
100
120
140
160
DSMM
LF
SF
US
a
a
a
a
-20
0
20
40
60
80
100
120
140
160
DSMM
LF
SF
US
Fig.
5.
Nitrogen
fertilizer
replacement
value
of
applied
total
N
(NFRV)
and
NH
4
-N
(NFRV
NH4-N
)
in
maize
(%)
at
Montanaso
Lombardo
(Italy).
DSMM:
unseparated
digestate
from
a
mix
of
cattle
slurry
and
maize;
LF:
liquid
fraction
of
DSMM;
SF:
solid
fraction
of
DSMM;
US:
untreated
cattle
slurry.
Significant
differences
(P
<
0.05)
among
treatments
within
a
year
are
indicated
by
letters
(HSD
Tukey
test).
40
D.
Cavalli
et
al.
/
Europ.
J.
Agronomy
73
(2016)
34–41
Table
5
Soil
mineral
nitrogen
(SMN
in
kg
N
ha
−1
:
sum
of
NO
3
-N
and
NH
4
-N)
as
a
result
of
fertilization
during
three
growing
seasons
at
Montanaso
Lombardo
(Italy).
Letters
indicate
significant
differences
among
treatments
within
year
and
sampling
date
(P
<
0.05)
(HSD
Tukey
test).
Season
Date
CON
AS
DSMM
LF
SF
US
2011–2012
Pre-spreading
25/05/2011
36.6a
32.9a
35.1a
40.9a
36.7a
37.7a
Maize
V3
06/20/2011
44.8a
87.2b
73.6ab
79.2ab
45.8a
55.8ab
Maize
V6
06/29/2011
55.7a
93.5b
72.6ab
76.1ab
48.2a
54.6a
Maize
V9
07/12/2011
18.2a
54.9a
31.0a
27.4a
19.9a
23.8a
Maize
R1
08/06/2011
6.1a
14.9a
6.7a
17.4a
10.1a
6.0a
Maize
R5
09/13/2011
4.7a
11.7a
5.8a
5.9a
6.7a
5.5a
Italian
ryegrass
harvest
05/10/2012
2.1a
1.5a
0.8a
1.7a
3.7a
2.7a
2012–2013
Maize
V3
06/08/2012
23.5a
85.4a
83.0a
90.3a
39.9a
39.1a
Maize
V6
06/18/2012
26.8a
131.6b
37.0b
54.8b
38.2b
32.2b
Maize
V9
07/02/2012
20.2a
52.1a
25.5a
33.8a
39.7a
30.3a
Maize
R1
05/25/2012
8.2a
17.0a
11.6a
10.2a
16.4a
7.9a
Maize
R5
08/30/2012
11.4a
11.9a
13.2a
15.4a
27.6b
13.2a
Italian
ryegrass
harvest
05/23/2013
5.6a
5.9a
7.7ab
6.1a
9.6b
6.2a
2013–2014
Maize
V3
07/01/2013
35.6a
61.2b
58.4b
46.2ab
57.5b
58.9b
Maize
V6
07/15/2013
39.9a
63.0b
49.7ab
53.9ab
59.3b
45.2ab
Maize
V9
07/22/2013
55.3a
85.6a
58.9a
58.7a
74.7a
55.9a
Maize
R1
08/13/2013
11.0a
17.0a
11.4a
11.3a
14.2a
9.4a
Maize
R5
(0–30
cm)
10/03/2013
6.4a
7.6ab
9.8b
10.4b
13.6c
10.6b
Maize
R5
(30–60
cm)
10/03/2013
6.1a
7.1a
9.1ab
8.4a
12.1b
9.2ab
Italian
ryegrass
harvest
(0–30
cm)
05/14/2014
9.3a
9.9a
11.4a
12.0a
16.0a
17.1a
Italian
ryegrass
harvest
(30–60
cm)
05/14/2014
6.5a
5.0a
7.9a
8.9a
10.3a
10.3a
a
V3:
maize
third
leaf;
V6:
maize
sixth
leaf;
V9:
maize
nineth
leaf;
R1:
maize
flowering;
R5:
maize
dent
maturity
(silage
harvest).
b
CON:
unfertilized
soil;
AS:
ammonium
sulphate;
DSMM:
unseparated
digestate
from
a
mix
of
cattle
slurry
and
maize;
LF:
liquid
fraction
of
DSMM;
SF:
solid
fraction
of
DSMM;
US:
untreated
cattle
slurry.
c
Pre-spreading
SMN
concentrations
in
2012
and
2013
were
equal
to
those
measured
at
Italian
ryegrass
harvest.
Both
DSMM
and
LF
had
low
C
to
organic
N
ratios
(
and
had
DMs
rich
in
soluble
compounds
(39–41%,
Their
decom-
position
presumably
induced
low
N
immobilization
in
soil
as
the
like
values
for
ANR
NH4-N
(
in
all
three
years
in
these
treatments
(with
the
exception
of
LF
in
2012)
and
in
AS
demonstrated
(
On
the
contrary,
SF
and
US
presumably
induced
net
N
immobilization
in
soil
as
a
consequence
of
their
high
C
to
organic
N
ratios
and
the
highly
cellulosic
and
hemicellulosic
DMs
Moreover,
about
8%
of
US
DM
was
made
of
VFAs,
which
have
been
shown
to
promote
N
immobilization
during
microbial
decomposition
(
The
yearly
application
of
SF
and
US
from
2011
to
2013
increased
ANR
NH4-N
values
during
the
three
years,
such
that
the
2013
ANR
NH4-N
no
longer
differed
from
that
of
AS
(
Such
marked
ANR
NH4-N
increase
in
2012
and
2013
for
SF
and
US
is
consistent
with
the
results
of
might
be
ascribed
to
residual
N
effect,
i.e.,
to
the
mineralization
of
applied
organic
N
after
its
application
year
(
Nitrogen
residual
effect
might
also
explain
several
other
findings:
(i)
higher
AGB
and
N
uptake
in
Italian
ryegrass
with
SF
compared
to
other
treatments
(
the
increase
in
ANR
NH4-N
from
2011
to
2012
in
SF
and
US
was
higher
than
the
increase
in
ANR
NH4-N
measured
in
DSMM
and
LF
in
the
same
period
(as
shown
also
by
(iii)
significantly
higher
SMN
at
maize
har-
vest
in
SF
compared
to
most
of
the
other
treatments
in
2012
and
2013.
Continuing
the
experiment
for
more
years
will
show
to
what
extent
the
residual
effect
continues
to
increase
N
recovery
in
US
and
SF
treatments.
Furthermore,
for
these
manures,
it
may
be
appropri-
ate
to
cultivate
a
catch
crop
to
intercept
overwinter
mineralized
N
(3–6%
of
applied
N
in
our
situation)
to
prevent
potential
N-leaching.
5.
Conclusions
For
manures
with
high
C
to
organic
N
ratios
(average
of
19
and
28
for
untreated
cattle
slurry
and
the
solid
fraction
of
digestate,
respectively),
the
results
made
evident
that
in
the
first
two
years
after
application,
when
residual
effects
are
not
yet
noticeable,
it
is
inadequate
to
estimate
the
NFRV
of
the
manures
as
equal
to
their
NH
4
-N
to
total
N
ratio.
In
fact,
in
such
cases,
net
N
mineralization
occurred
months
after
application,
necessitating
mineral
fertilizer
application
to
compensate
for
N
immobilization
to
satisfy
crop
N
requirements.
For
manures
with
lower
C
to
organic
N
ratios
(such
as
12
in
this
case
for
unseparated
digestate
from
a
cattle
slurry-maize
mix),
the
ammonium
to
total
N
ratio
of
the
manure
can
serve
as
a
proxy
for
the
NFRV
beginning
in
the
first
application
year.
Results
for
the
liq-
uid
fraction
of
the
digestate
were
intermediate,
despite
its
similar
C
to
organic
N
ratio
and
similar
fiber
composition
and
VFA
content
as
that
of
the
digestate.
Acknowledgements
We
gratefully
acknowledge
the
contributions
of
Prof.
Tommaso
Maggiore,
Prof.
Efisio
Piano,
and
Prof.
Pierluigi
Navarotto
in
concep-
tion
and
development
of
the
SINBION
project.
Research
work
was
carried
out
within
the
SINBION
project
(Sviluppo
di
sistemi
inte-
grati
sostenibili
per
il
recupero
dei
sottoprodotti
dell’agro-industria
e
dell’azienda
agraria
al
fine
di
ottimizzare
la
produzione
di
biogas
e
valorizzare
l’utilizzazione
agronomica
del
digestato;
Integrated
systems
for
biogas
and
nitrogen)
and
funded
by
the
Italian
Ministry
of
Agriculture
D.M.
n
◦
27335/7303/10
(December
2
2012).
References
AOAC
International,
1995.
Bechini,
L.,
Marino,
P.,
2009.
Burton,
C.H.,
2007.
Cavalli,
D.,
Cabassi,
G.,
Borrelli,
L.,
Fuccella,
R.,
Degano,
L.,
Bechini,
L.,
Marino,
P.,
2014.
D.
Cavalli
et
al.
/
Europ.
J.
Agronomy
73
(2016)
34–41
41
Chantigny,
M.H.,
Angers,
D.A.,
Bélanger,
G.,
Rochette,
P.,
Eriksen-Hamel,
N.,
Bittman,
S.,
Buckley,
K.,
Massé,
D.,
Gasser,
M.,
2008.
de
Boer,
H.C.,
2008.
Ewen,
A.,
2011.
Grigatti,
M.,
Di
Girolamo,
G.,
Chincarini,
R.,
Ciavatta,
C.,
Barbanti,
L.,
2011.
Gutser,
R.,
Ebertseder,
Th.,
Weber,
A.,
Schraml,
M.,
Schmidhalter,
U.,
2005.
Hernández,
D.,
Polo,
A.,
Plaza,
C.,
2013.
Herrmann,
A.,
Sieling,
K.,
Wienforth,
B.,
Taube,
F.,
Kage,
H.,
2013.
Hjorth,
M.,
Christensen,
K.V.,
Christensen,
M.L.,
Sommer,
S.G.,
2010.
Holm-Nielsen,
J.B.,
Al
Seadi,
T.,
Oleskowicz-Popiel,
P.,
2009.
Kirchmann,
H.,
Lundvall,
A.,
1993.
Mertens,
D.R.,
2002.
Möller,
K.,
Müller,
T.,
2012.
Møller,
H.B.,
Lund,
I.,
Sommer,
S.G.,
2000.
Möller,
K.,
Stinner,
W.,
Deuker,
A.,
Leithold,
G.,
2008.
Morvan,
T.,
Nicolardot,
B.,
2009.
Morvan,
T.,
Nicolardot,
B.,
Péan,
L.,
2006.
Mu ˜
noz,
G.R.,
Kelling,
K.A.,
Powell,
J.M.,
Speth,
P.E.,
2004.
Nevens,
F.,
Reheul,
D.,
2005.
Peters,
K.,
Jensen,
L.S.,
2011.
Plénet,
D.,
Lemaire,
G.,
1999.
Reijs,
J.W.,
Sonneveld,
M.P.W.,
Sørensen,
P.,
Schils,
R.L.M.,
Groot,
J.C.J.,
Lantinga,
E.A.,
2007.
Ritchie,
S.W.,
Hanway,
J.J.,
Benson,
G.O.,
1996.
How
a
corn
plant
develops.
Spec.
Rep.
48.
Rev.
ed.
Iowa
State
Univ.
Coop.
Ext.
Serv.,
Ames.
Saunders,
O.E.,
Fortuna,
A.,
Harrison,
J.H.,
Whitefield,
E.,
Cogger,
C.G.,
Kennedy,
A.C.,
Bary,
A.I.,
2012.
Schröder,
J.J.,
2005.
Schröder,
J.J.,
Jansen,
A.G.,
Hilhorst,
G.J.,
2005.
Schröder,
J.J.,
Uenk,
D.,
Hilhorst,
G.J.,
2007.
Schröder,
J.J.,
de
Visser,
W.,
Assinck,
F.B.T.,
Velthof,
G.L.,
2013.
Sieling,
K.,
Herrmann,
A.,
Wienforth,
B.,
Taube,
F.,
Ohl,
S.,
Hartung,
E.,
Kage,
H.,
2013.
Sommer,
S.G.,
Hutchings,
N.J.,
2001.
Sørensen,
P.,
1998.
Sørensen,
P.,
2004.
Sørensen,
P.,
Weisbjerg,
M.R.,
Lund,
P.,
2003.
Van
Kessel,
J.S.,
Reeves
III,
J.B.,
2002.
Van
Kessel,
J.S.,
Reeves
III,
J.B.,
Meisinger,
J.J.,
2000.
Van
Soest,
P.J.,
1963.
Van
Soest,
P.J.,
Robertson,
J.B.,
Lewis,
B.A.,
1991.
Webb,
J.,
Sørensen,
P.,
Velthof,
G.,
Amon,
B.,
Pinto,
M.,
Rodhe,
L.,
Salomon,
E.,
Hutchings,
N.,
Burczyk,
P.,
Reid,
J.,
2013.
Zavattaro,
L.,
Monaco,
S.,
Sacco,
D.,
Grignani,
C.,
2012.