Biomass production in

multispecies and grass

monoculture swards under

cutting and rotational grazing

Rosemary Collins (AU-IBERS), Rémy

Delagarde (INRA-Saint-Gilles) and Sébastien

Husse (Agroscope)

Experiment was carried out as part of

FP7 project ‘Multisward’

Structure

A brief description of CONTEXT

The RATIONALE behind the experiment

How this work fitted into MULTISWARD

The main RESULTS:

• Effects of sward type

• Effects of grazing animal

• Species dynamics

Some CONCLUSIONS

Throughout this presentation

‘MSS’ = multispecies swards

Context

Some background…

Ecological research shows that the production of plant biomass is enhanced by

species diversity

BUT

This has mostly been carried out in species-rich and nutrient-poor systems (low

productivity)

Can we extend these results to fertile agricultural systems (high productivity)?

Studies have shown yield benefits of MSS over

pure stands under cutting e.g. COST 852

project

0

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40

60

80

100

120

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160

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200

High yielding sites Low yielding sitesRelative yield

advantage of

average mixture

vs. monoculture

(%)

Site

From Finn et al.,

2013, J. Appl. Ecol.

50, 365-375

Here, the yield benefit of mixtures was observed across a

range of site productivities over a 3-year period – so not

restricted to ‘low yielding’ sites

This increased productivity in MSS results

from diversity effects due to:

- Niche differentiation (improved use of resources in space or

time)

- Facilitation (positive interactions between species e.g. legume-

grass N-sparing or N-transfer processes)

Rationale

Q: Can we extend ‘ecological’ results to

productive agricultural systems?

A: Yes, but the impact of grazing by large

herbivores needs more research.

In this experiment we analysed responses

of MSS to grazing, with cutting

management as a reference

How did this research contribute

to Multisward?

A ‘Common Experiment’ (CE) was

carried out in many sites as part of

Multisward Work Package 2.

Some sites in the CE added grazing

animals.

Sites/Institutes involved in CE

Agroscope (1) CH

Tänikon

AU-IBERS (2) UK

Aberystwyth

INRA (3) FR

Rennes

PULS (4) PL

Brody; Szelejewo

UMB (5) NO

Ås

1

2

3

4

5

This achieved a good geographical spread across Europe, adding significant

value to the results. These sites added the grazing element: 1, 2 & 3

Site Sward dynamics,

DM yield

Grazing animal Animal

production

AU-IBERS

cut vs grazed+ Sheep

Agroscope

cut vs grazed+ Beef cattle

INRA-Rennes

cut vs grazed+ Dairy cows +

PULS (2 sites)

cutting only+ No

UMB

cutting only+ No

This presentation focuses on the three sites with a grazing

component.

Multisward CE Structure

Composition of MSS:

First step was to select

appropriate mixture components

Choice of species

• Research has shown that strong ecosystem responses to

species number can occur at low levels of species richness e.g. 4

species (Kirwan et al., 2007, J. Ecol. 95, 530-539)

• Therefore, the selection of a small number of species with

appropriate functional traits can potentially deliver positive

ecosystem responses

• MSS can be strategically designed to maximise:

- niche complementarity

- interspecific interactions Improved resource utilisation

Increased production of

biomass of high forage

quality

Choice of species

• For the Multisward CE we used a ‘functional group’ approach to species

selection.

• Species were strategically selected to maximise the diversity effect, whilst

also being of agronomic relevance.

• We combined a ‘shallow’ vs ‘deep’ rooting species contrast within a

‘non N-fixing’ vs ‘N-fixing’ contrast.

• Four selected species in the multi-species mixtures were:

1. Non-fixing species [shallow] Non-fixing 1 = perennial ryegrass

2. Non-fixing species [deep] Non-fixing 2 = tall fescue or chicory

3. N-fixing species [shallow] Legume 1 = white clover

4. N-fixing species [deep] Legume 2 = red clover

This combination should maximise niche complementarity and

provide opportunities for positive interspecies interactions to occur

Sward

types

Non-fixing

1: PRG

Non-fixing

2: Tall

fescue or

chicory

Legume 1:

White clover

Legume 2:

Red clover

1 M1 0 0 0

2 2/3 1/3 0 0

3 2/3 0 1/6 1/6

4 1/2 1/6 1/6 1/6

5 1/3 1/3 + 1/2 1/2 1/4

1 H1 0 0 0

Sward types included in the CE

1M = Moderate-N PRG monoculture

1H = High-N PRG monoculture treatment (x 2 level of N fertiliser applied to the other sward types)

Fractions refer

to the

proportion of

the

monoculture

sowing rate in

common use at

each site

The 5-spp mixture was

only implemented in

INRA-Rennes

We compared the productivity of MSS with that of the current agronomic standard

(highly fertilized pure stands of perennial ryegrass).

Measurements

What the CE measured:

• We quantified sward DM yields under

rotational grazing: biomass accumulation and removal to a

target sward height

cutting: mechanical cutting to the same height

• Sward types under cutting/grazing received the same external N

inputs and were defoliated at the same time, providing a robust

comparison of these managements.

Results

1. Beef cattle grazing to 6 cm

Agroscope

Cumulative total DM yield (kg/ha): 18 harvests

Sward type

High N PRG

(350 kgN/ha/yr)

• Averaged over sward

type, yield under

grazing was higher

than under cutting.

• Sward types 3, 4

(legume-based) and

1H (high N PRG mono)

were highest yielding,

averaged over

management.

• No sward type x

management

interaction occurred.

+ Legume

High N PRG

300 kgN/ha/yr

2. Sheep grazing to 5 cm

AU-IBERS

Cumulative total DM yield (kg/ha): 12 harvests

Sward type

+ Legume

• Yields were higher

under cutting, and in

sward types 3 and 4

(legume-based).

• An interaction between

management and sward

type was due to

differential response of

legume (3 and 4) and

non-legume (1, 2)

based sward types to

grazing. Grazing

reduced yields in

legume-based mixtures,

when compared with

cutting.

In this site CUT

plots were set

up only in

Treatments 1M

and 1H (low- and

high-N perennial

ryegrass

monocultures).

The site used

an extra

treatment (5

spp), instead of

treatment 2.

Sward type

High N PRG

165 kgN/ha/yr

3. Dairy cows grazing to 4 cm

INRA-Rennes

Cumulative total DM yield (kg/ha): 13 grazing harvests; 10 cutting harvests

Grazed yield in 1M* calculated

from 10 harvests to allow a direct

comparison with cut yield

+ Legume

INRA-Rennes

Within the cutting management, sward type 1H (high N

PRG mono) was higher yielding than 1M (moderate N

PRG mono).

No effect of cutting vs grazing management on yields

in 1M*.

No effect of sward type on yields under grazing.

DM yield: Conclusions

1. There were different responses of sward types to management at

different sites – could be due to using different grazing animals. Sheep

and cattle differ in their species selectivity when grazing.

Sheep grazing reduced the yield of legume-based swards (AU-IBERS),

whereas cattle grazing did not have this effect (Agroscope, INRA-

Rennes).

2. Our results show that there was no detriment to sward yield in

legume-based MSS compared to high N PRG monos under either

cutting or grazing.

This represents a substantial economic and environmental saving.

A quick look at legume species dynamics

(AU-IBERS)

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Start Yr1

Start Yr2

End Yr 2 Start Yr3

End Yr 3

% S

ow

n S

pe

cie

s D

M

Grazed white clover

3

4

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100

Start Yr1

Start Yr2

End Yr 2 Start Yr3

End Yr 3

% S

ow

n S

pe

cie

s D

M

Cut white clover

3

4

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100

Start Yr1

Start Yr2

End Yr 2 Start Yr3

End Yr 3

% S

ow

n S

pe

cie

s D

M

Grazed red clover

3

4

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Start Yr1

Start Yr2

End Yr 2 Start Yr3

End Yr 3

% S

ow

n S

pe

cie

s D

M

Cut red clover

3

4

%WC decreased during each

summer, when plots were

grazed

%WC remained fairly stable

under cutting

%RC had decreased

substantially under grazing by

end of Yr 2

%RC decreased

substantially by end of Yr 2,

but was still present

Sward type

Legume species dynamics: Conclusions

Under rotational sheep grazing, %legume contribution to

sward yield over time was vulnerable.

This was particularly the case in red clover.

Under cutting, white clover maintained a stable contribution of

c. 35%.

%red clover decreased sharply, but still maintained a useful c.

10% contribution.

Management is key for legume persistence:

The grazing regime implemented in Aberystwyth

did not promote legume biomass

Thanks

• To my co-authors

• To fellow participants in the Multisward Common Experiment

• To my colleagues in AU-IBERS for all their help

• To you for your attention

Any

questions?