Europ.

 

J.

 

Agronomy

 

73

 

(2016)

 

34–41

Contents

 

lists

 

available

 

at

 

ScienceDirect

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

a

,

∗

,

 

Giovanni

 

Cabassi

b

,

 

Lamberto

 

Borrelli

b

,

 

Gabriele

 

Geromel

a

,

Luca

 

Bechini

a

,

 

Luigi

 

Degano

b

,

 

Pietro

 

Marino

 

Gallina

a

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

 

(

Schröder,

 

2005

).

 

Both

 

indices

 

can

also

 

be

 

calculated

 

for

 

ammonium-N

 

(NH

4

-N)

 

provided

 

by

 

different

manures.

Many

 

laboratory

 

incubations

 

(

Bechini

 

and

 

Marino,

 

2009;

Morvan

 

et

 

al.,

 

2006;

 

Van

 

Kessel

 

and

 

Reeves,

 

2002

)

 

and

 

field

∗ Corresponding

 

author.

 

Fax:

 

+39

 

0250316575.

E-mail

 

address:

 

daniele.cavalli@unimi.it

 

(D.

 

Cavalli).

experiments

 

involving

 

untreated

 

(

Reijs

 

et

 

al.,

 

2007;

 

Schröder

 

et

 

al.,

2005,

 

2013;

 

Sørensen

 

et

 

al.,

 

2003

)

 

and

 

digested

 

manures

 

(

Chantigny

et

 

al.,

 

2008;

 

de

 

Boer,

 

2008;

 

Herrmann

 

et

 

al.,

 

2013;

 

Möller

 

et

 

al.,

 

2008;

Saunders

 

et

 

al.,

 

2012;

 

Sieling

 

et

 

al.,

 

2013;

 

Schröder

 

et

 

al.,

 

2007

)

 

have

shown

 

that

 

first-year

 

crop

 

available

 

N

 

often

 

approximates

 

the

 

NH

4

-

N

 

content

 

of

 

manure

 

(

Möller

 

and

 

Müller,

 

2012;

 

Webb

 

et

 

al.,

 

2013

),

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

 

(

Gutser

 

et

 

al.,

 

2005;

Schröder

 

et

 

al.,

 

2005,

 

2007;

 

Nevens

 

and

 

Reheul,

 

2005;

 

Hernández

et

 

al.,

 

2013

).

Digestates

 

typically

 

have

 

high

 

NH

4

-N

 

to

 

total

 

N

 

ratios

 

that

raise

 

their

 

potential

 

N

 

availability

 

for

 

crops

 

(

Gutser

 

et

 

al.,

 

2005;

Möller

 

and

 

Müller,

 

2012

).

 

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

 

(

Holm-Nielsen

 

et

 

al.,

 

2009

).

 

Moreover,

 

to

 

facil-

itate

 

the

 

fertilizer

 

use

 

of

 

both

 

digested

 

and

 

raw

 

manures,

 

their

 

liquid

and

 

solid

 

fractions

 

are

 

separated

 

(

Burton,

 

2007;

 

Hjorth

 

et

 

al.,

 

2010;

Møller

 

et

 

al.,

 

2000;

 

Möller

 

and

 

Müller,

 

2012

).

 

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

 

(

Möller

 

and

Müller,

 

2012

).

Experiments

 

that

 

evaluate

 

the

 

NFRVs

 

of

 

unseparated

 

digested

and

 

co-digested

 

manures

 

and

 

their

 

solid

 

or

 

liquid

 

fractions

 

are

 

still

scarce

 

(

Chantigny

 

et

 

al.,

 

2008;

 

Grigatti

 

et

 

al.,

 

2011

);

 

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

 

(

Cavalli

et

 

al.,

 

2014

)

 

to

 

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).

Cavalli

 

et

 

al.

 

(2014)

 

found

 

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

(

Fig.

 

1

).

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

 

(

Table

 

1

).

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

 

Table

 

2

)

 

mainly

 

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

a

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

a

Year

 

DM

b

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

 

Cavalli

 

et

 

al.

 

(2014)

 

and

 

are

 

reported

 

in

 

Table

 

1

.

 

Volatile

 

fatty

acids

 

(VFA)

 

were

 

determined

 

by

 

HPLC

 

(

Ewen,

 

2011

)

 

after

 

steam

 

dis-

tillation

 

according

 

to

 

procedure

 

DIN

 

38414–19

 

(1999)

 

(

Fig.

 

2

).

 

Ash

content

 

was

 

measured

 

after

 

incineration

 

in

 

a

 

muffle

 

at

 

550

◦

C

 

(

AOAC

International,

 

1995

)

 

(

Fig.

 

2

).

 

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

 

Mertens

 

(2002)

,

 

Van

 

Soest

 

et

 

al.

 

(1991)

 

and

Van

 

Soest

 

(1963)

,

 

respectively,

 

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

 

(

Fig.

 

2

).

2.3.

 

Above

 

ground

 

biomass

 

sampling

 

and

 

analysis

Above

 

ground

 

biomass

 

(AGB)

 

of

 

maize

 

was

 

sampled

 

at

 

the

following

 

phenological

 

stages

 

(

Ritchie

 

et

 

al.,

 

1996

):

 

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

 

Cavalli

 

et

 

al.

 

(2014)

 

with

 

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

 

Cavalli

 

et

 

al.

 

(2014)

.

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

 

(

Table

 

3

).

 

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

 

Plénet

 

and

 

Lemaire

 

(1999)

.

DSMM,

 

LF,

 

or

 

US;

 

on

 

the

 

contrary,

 

application

 

of

 

SF

 

enhanced

 

Italian

ryegrass

 

AGB

 

compared

 

to

 

AS

 

and

 

the

 

other

 

manures

 

(

Table

 

3

).

Maize

 

N

 

uptake

 

(

Table

 

4

)

 

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

 

(

Table

 

4

).

Fig.

 

3

 

reports

 

the

 

relationship

 

between

 

maize

 

AGB

 

and

 

its

 

N

 

con-

centration,

 

as

 

well

 

as

 

critical,

 

minimum,

 

and

 

maximum

 

N

 

dilution

curves

 

(

Plénet

 

and

 

Lemaire,

 

1999

).

 

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

 

(

Fig.

 

4

).

 

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

 

(

Fig.

 

5

).

 

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

a

Date

 

Treatment

b

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

 

(

Table

 

5

).

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

 

(

Fig.

 

4

),

 

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

 

(

Fig.

 

4

),

 

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

 

(

Sørensen,

 

2004;

 

Schröder

 

et

 

al.,

 

2007,

2013

).

 

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

a

Date

 

Treatment

b

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.