Managing competition and lucerne persistence with

sowing configuration

Richard C. Hayes, Matthew T. Newell, Keith G. Pembleton, Mark B. Peoples &

Guangdi D. Li

Can lucerne persistence be improved by changed spatial configuration at sowing?

Approach: 6 sites, 9 field experiments

Cowra

Condobolin

Bogan Gate

Wagga

EurongillyMirrool

Central West experiments n = 6 Treatments: 4 x crop +

4 x row configuration– Lucerne & sub clover with

wheat, barley, canola, lupin– Pure pasture, pure crop,

crop:pasture mix, crop:pasture (1:1)

Species sown concurrently, autumn 2013, repeated 2014

25 cm row spacing No fertiliser in the drill row

Riverina experiments

n = 3 10 treatments Combinations of lucerne, phalaris or

sub clover– Hayes et al. 2017, 2020

Species sown concurrently, autumn 2012

25 cm row spacing No fertiliser in the drill row

Year1 2 3 4

Luce

rne

dens

ity (p

lant

s/m

2 )

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40

60

80

BG Nil cropBG (1:1)BG (mix)Cdn Nil cropCdn (1:1)Cdn (mix)Cwa Nil cropCwa (1:1)Cwa (mix)

1 2 3

A) B)

Key findings: Lucerne density – Central West

Fig. 1. Change in lucerne density through time due to spatial configuration associated with wheat crop only at experiments sown at three sites in the Central West in A) 2013, and B) 2014. Error bars show l.s.d. at P = 0.05 on dates where a significant site x treatment interaction was observed. Abbreviations: BG, Bogan Gate; Cdn, Condobolin; Cwa, Cowra; Past-only, Pasture-only; 1:1, Pasture-crop (1:1); (mix), Pasture-crop (mix).

2013 2014

Climatic conditions – Central West

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Bogan Gate Condobolin Cowra

Summer rainfall (mm)

2013/14 2014/15 2015/16

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Bogan Gate Condobolin Cowra

Cumulative day degrees (C)

2013/14 2014/15 2015/16

Final lucerne density – Central West

Excavated 8540 plants from 1m x 1m quadrats (n = 382)!

Experimenta b c d e f

Pasture-onlyPasture-crop (1:1)Pasture-crop (mix)

B)

Luce

rne

dens

ity (p

lant

s/m

2 )

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Fig. 2. Site x spatial configuration effects on final lucerne density across the six experiments in the Central West. Data from individual experiments are marked according to letter; Bogan Gate sown in 2013 (a) and 2014 (b), Condobolin sown in 2013 (c) and 2014 (d), Cowra sown in 2013 (e) and 2014 (f).

≈

Summary – Central West sites

Lucerne in all experiments (except Cowra 2014) ↓ with time The presence of a cover crop in yr 1 ↓ final lucerne

density by 39% No advantage to lucerne persistence of separating

from crop (at 25 cm spacings) Lucerne density was maintained in summers with ≥

100 mm rainfall and ≤ 2150 day degrees

Lucerne density, Riverina

2012 2014

Luce

rne

dens

ity (

plan

ts/m

2 )

10

20

30

40

50

60Eurongilly Mirrool Wagga

2012 2014

Luc-only Luc-sub(1:1) Luc-sub(1:2) Luc-sub(mix) Phal-luc(1:1) Phal-luc(1:2) Phal-luc(mix)

A) B)

Fig. 3. The effect of A) site and, B) row configuration on lucerne density at the start (2012) and at the conclusion (2014) of the Riverina experiments. Error bars show l.s.d. at P = 0.05.

Site Row configuration

Climatic conditions - Riverina

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Eurongilly Mirrool Wagga

Summer rainfall (mm)

2012/13 2013/14

2100

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2240

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2300

Eurongilly Mirrool Wagga

Cumulative day degrees (C)

2012/13 2013/14

Establishment density = 55 plants/m2

= 14 plants/m drill row

= 28 plants/m drill row

= 37 plants/m drill row

Plant location – end of pasture phase

‘On’ lucerne dril row

‘Close to’ lucerne dril row

Plant location – Riverina (year 3)

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Lucerne Phalaris Sub clover

Plants on or close to original drill row

%

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Eurongilly Mirrool Wagga

Sub clover plants on or close to original drill row

%

93%

Plant location – Central West

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Bogan Gate Condobolin Cowra

Sub clover plants on or close to the original drill row (%)

2013 2014

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Pasture only Pasture-crop 1:1 Pasture-Crop mix

Sub clover plants on or close to the original drill row

%

The majority of plants stayed on or close to the original drill row during the pasture phase, especially in hotter environments.

Photos from Mirrool…

Lucerne:Sub 1:1, Feb 2014 Lucerne:Biserrula 1:1, June 2014

Pure vs. mixed lucerne swards

Ground cover - Riverina

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70

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Luc Sub1:2

Luc Phalmix

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Luc Phal2:1

Ground cover (Feb-Mar; %)

Ground cover (%)

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Groundcover (Feb-Mar; %)

%

Soil water, Wagga

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Plant available water (Apr 2015)

PAW (0-0.6 m; mm)

Litte

r cov

er (%

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Bare ground (%)0 20 40 60 80 100

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A)

B)

y = -1.041x + 90.405r2 = 0.91 Relationship between bare

ground and litter cover (Central west sites; n=288)

Cumulative DM (t/ha), Wagga

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Luc only Luc Submix

Luc Sub1:1

Luc Sub1:2

Luc Phalmix

Luc Phal1:1

Luc Phal2:1

Year 3 DM, Wagga

t/ha

Light interception data

Bogan Gate Condobolin Cowra

Ligh

t int

erce

ptio

n (%

)

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Barley Canola Lupin Wheat

Eurongilly Wagga Wagga

Luc-only Luc-sub(1:1) Luc-sub(1:2) Luc-sub(mix)Phal-luc(1:1)Phal-luc(1:2)Phal-luc(mix)

A) B)

The effect of crop and pasture type on light interception sampled in spring 2014 at A) the Central West (year 1), and B) Riverina sites (year 3).

Pure lucerne swards = poor resource-use efficiency

Implications: Targets for establishment

Maintaining >50 plants of lucerne in dryland stands is possible (eg Cowra 2014) but unlikely in these hot-summer environments. Therefore, shouldn’t aim to establish >50 plants/m2

Estab. densities ≤ 28 plants/m row should be targeted These benchmarks will help growers/advisors gauge

success Row configuration will not help to increase lucerne density

Implications: Increasing productivity Lucerne productivity is correlated with density Cover crops ↓ lucerne density by ≈ 40%

– Competition for light in year 1 Otherwise, density is driven by summer conditions Phalaris/sub clover had little effect on lucerne density

– Phalaris/sub have ↓ activity over summer

Suggestion: Productivity ↑ of lucerne swards in dryland environments seems more likely by tweaking companion species than by trying to increase the density of lucerne

In an ideal world…

1. Sow lucerne into standing stubble2. Sow on as narrow a row spacing as possible3. Monitor lucerne establishment density4. Sow with winter growing companions

1. Phalaris?2. Annual legumes (small-seeded)

5. ‘Sow’ the annual legumes in the lucerne row & between the row (scatter plates, residual seed bank)

richard.hayes@dpi.nsw.gov.au

Thanks to:

Susan Langfield, Richard Lowrie (NSW DPI) & Tony Swan (CSIRO)

Estimating lucerne density

Basal frequency (%)0 20 40 60 80

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rne

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ity (p

lant

s/m

2 )

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y = 0.0047x2 + 1.244x - 1.4928R2 = 0.73

A)

Fig. 4. The relationship between basal frequency and lucerne density (n=382)

Key message: Basal frequency over-estimated density by up to 30% in the range 15-82 plants/m2