Yield-scaled N2O emissions in pastures: effect of earthworm (EW) activity and

fertilizer (F) addition Sebastian Yanore MSc. Thesis, end colloquium 29-03-2016

Supervisors: Ingrid Lubbers, Jan Willem van Groenigen

N2O emissions

Potent greenhouse gas Ozone depleting substance 70% emitted from agricultural activities (UNEP,

2013) 21% of agricultural lands in Europe is used for

grassland production 18% of N2O emissions in Europe comes from

pasture lands

NO3- N2NO2

- NO

NH3 NH4+ NH2OH NO2

- NO3-Nitrification

Denitrification

(Nitrifier Denitrification)

N2O

N2O

(Wrage et al.,2004)

How is N2O formed in soil?

Oxygen

Soil structure

N2OSubstrateAvailabilit

y(N,C)

Soil mesofaun

aeg EW

Moisture content

(Porre et al., 2015)

Factors controlling N2O formation in soil?

• It describes the N2O efficiency of a cropping system

Yield-scaled N2O emissions

(Van Groenigen et al., 2010)

What is known?

What is known?

What is known?

What is known?

What is known?

How EW increase N2O emissions

How EW increase crop production

What is known?

How EW activity affects the amount of N2O emitted per unit dry matter of a pasture system

How EW density affects yield-scaled N2O emissions of different pasture systems

How fertilizer addition changes the effect of EW on the amount of N2O emissions per unit dry matter of a pasture system

What is not known?

H1: EW presence increases yield-scaled N2O emission of clover, has no effect on yield-scaled N2O emission of grass, and increases slightly the yield-scaled N2O of the mixed pasture

Hypotheses

Yield

Yield

N2O

Grass, YSE =

Mixture, YSE=

Clover, YSE=

YSE =

H2: Higher EW density increases crop yield, but does not affect N2O emissions, and thus lower yield-scaled N2O emissions for the three different pastures in an order grass-mixture-clover

Hypotheses

H3: Addition of fertilizer increases the effects of EW on yield-scaled N2O emissions of all three pastures

Hypotheses

Experiment

60 days greenhouse experiment Intact soil columns Steam sterilized once at 700C for 3.5

hrs Normal EW density: 175 individuals

m-2

High EW density: 350 individuals m-2

(Didden,2010)

Experiment Fertilization: Mixture of farm yard

manure and composted fodder at ~25 kg N kg ha-1 yr-1

Trifolium repens (clover) at 6 kg ha-1

Lolium perenne (grass) at 45 kg ha-1

Clover-grass mixture at 3 and 23 kg ha-1 Starter gift: cow manure grains at 45 kg

N kg ha-1 yr-1

TreatmentsTreatment code

EW additions

Fertilization

Replicates

Control No No 5EN Normal No 5EH High No 5F No Yes 5FEN Normal Yes 5

In total: 5 treatments × 3 plant community × 5 reps = 75 columns Completely randomised into 5 blocks

N2O fluxes 25 times in 60 days Biomass harvest

Three cuts Moisture content with TDR Soil sampling with auger Destructive sampling: EW, soil

samples

Measurements

Clover Grass Mixture0

5

10

15

20

25

Cum

ulat

ive

N2O

-N e

mis

sion

(m

g N

2O-N

m

-2)

a

b

a

Results: cumulative N2O emission of pasture systems

Cont

rol

EH EN

F

FEN

Cont

rol

EH EN

F

FEN

Cont

rol

EH EN

F

FEN

Clover Grass Mixture

0

5

10

15

20

25

30

35

40

Cum

ulat

ive

N2O

-N e

mis

sion

(m

g N

2O-

N m

-2)

Treatments effect on cumulative N2O emission

Results

Clover Grass Mixture0

2

4

6

8

10

12

14

16

Yiel

d (g

m-2

) a

b b

Yield(DM) of pasture systems

Results

Cont

rol

EH EN

F

FEN

Cont

rol

EH EN

F

FEN

Cont

rol

EH EN

F

FEN

Clover Grass Mixture

0

2

4

6

8

10

12

14

16

18

Yiel

d (g

m-2

)Treatments effect on yield(DM)

Results

Clover Grass Mixture0

0.5

1

1.5

2

2.5

3

3.5

Yiel

d-sc

aled

N2O

-N e

mis

sion

s (m

g N

2O-N

g-

1)

a a

b

Yield-scaled N2O emission

Results

Treatments effect on yield-scaled N2O emission

Cont

rol

EH EN

F

FEN

Cont

rol

EH EN

F

FEN

Cont

rol

EH EN

F

FEN

Clover Grass Mixture

0

1

2

3

4

5

6

Yiel

d-sc

aled

N2O

-N e

mis

sion

s (

mg

N2O

-N g

-1)

Results

R = +0.64, P < 0.001

Results

Water filled pore space (%WFPS)

R = -0.79P < 0.001

Results

Water filled pore space (%WFPS)

R = + 0.67 P < 0.001

Results

Water filled pore space (%WFPS)

H1: EW presence increases yield–scaled N2O emission of clover, has no effect on yield–scaled N2O emission of grass, and increases slightly the yield-scaled N2O emission of the mixed pasture

Borten et.al., 2000, Rizhiya et.al., 2007

✓✗✗

Cont

rol

EH ENF

FEN

Cont

rol

EH ENF

FEN

Cont

rol

EH ENF

FEN

Clover Grass Mixture

0

1

2

3

4

5

6

Yiel

d-sc

aled

N2O

-N e

mis

sion

s (m

g N

2O-N

g-1

)

Results and discussion

Cont

rol

EH ENF

FEN

Cont

rol

EH ENF

FEN

Cont

rol

EH ENF

FEN

Clover Grass Mixture

0

1

2

3

4

5

6

Yiel

d-sc

aled

N2O

-N e

mis

sion

s (m

g N

2O-N

g-1

)✗ H2: Higher EW density

increases crop yield, but does not affect N2O emissions, and thus lower yield-scaled N2O emissions for the three different pastures in an order grass-mixture-clover

Results and discussion

H3: Addition of fertilizer increases the effects of EW on yield-scaled N2O emissions of all three pastures

~25 kg N kg ha-1 yr-1

✗Co

ntro

lEH EN

FFE

NCo

ntro

lEH EN

FFE

NCo

ntro

lEH EN

FFE

N

Clover Grass Mixture

0

1

2

3

4

5

6

Yiel

d-sc

aled

N2O

-N e

mis

sion

s (m

g N

2O-N

g-1

)

Results and discussion

As simulated rainfall was constant for all treatments and clover establishment was slow due to sterilization-induced growth inhibition, %WFPS was significantly higher in the clover monocultures

We conclude that neither earthworm activity nor composted manure addition nor their interaction were determinants of yield-scaled N2O emission

Instead, in our experiment increased %WFPS was the driving factor for yield-scaled N2O emissions

Conclusions

A long(er) duration in the field At least one month after sterilization before

seeding Establishment of clover before grass in the a

mixed pasture system

Research recommendations

My supervisors: Ingrid Lubbers and Jan Willem van Groenigen

Gerlinde De Deyn CBLB André Maassen and John van

der Lippe

Acknowledgements

Thank You!