enemies of pasture establishment and legume regeneration ...€¦ · enemies of pasture...

Enemies of pasture establishment and

legume regeneration

Dr Belinda Hackney

Paddock Priorities and other factors that might be affecting

nodulation

Belinda Hackney – CWLLS, Forbes

Key issues

• Identifying what you have - Priorities

• Choosing tactics - Altering what you have

- Changing what you have

Paddock priorities

• Given 10 paddocks on your farm, how do you

prioritise where to allocate inputs?

Paddock priorities…….an example 10 paddocks

Paddock priorities 10 paddocks

2 paddocks 8 paddocks

Poor soil depth Good soil depth



1 paddock 1 paddock 6 paddocks 2 paddocks


Low fertility High fertility Poor legume content Good legume content




2 paddocks 4 paddocks 1 paddock 1 paddock



Low fertility High fertility Low weed burden High weed burden





1 paddock 1 paddock 3 paddocks 1 paddock




Good drainage Poor drainage High litter load Low litter load






2 paddocks 1 paddock





Low fertility High fertility












Maintain












Maintain Fertiliser












Maintain Fertiliser

Graze in summer/autumn












Maintain

Fertiliser

Fertiliser













Maintain

Fertiliser

Fertiliser

Might be as good as it can be?

Grazing management Wrong spp.?













Maintain

Fertiliser

Fertiliser



Herbicide, grazing management

fertility?













Maintain

Fertiliser

Fertiliser




fertility? Herbicide, grazing management,

fertility, species suitability?













Maintain

Fertiliser

Fertiliser







Maintain












Maintain

Fertiliser

Fertiliser







Maintain

Is it worth it?

Options

Procrastinate Renovate Manipulate Maintain

Options

Renovate Manipulate

Exploitable Difference • Grazing • Grazing plus herbicide • Selective herbicides • Non-selectives • Non-selective herbicides selectively

• +/- grazing • Introduction of other species

• Broadcast • Drill

• What’s the baseline • Different species and potential

Choose wisely – create exploitable differences

• Preparation • Species choice - tolerance to limitations - hardseededness/maturity time - dormancy - appropriate mixes • Fertiliser choice • Legume inoculation • Sowing rate • Sowing technique • Sowing depth • Sowing time

Introducing other species into established

pastures

Common questions – ‘What can I grow with established……’

- Perennial pasture – grass or lucerne

Need to think about: - Site preparation

- ground cover

- retarding existing pasture?

- Moisture availability

- Method of introduction

- Rate of introduction

Space

Moisture Light


pastures - moisture

Common questions – ‘What can I grow with established……’

- Perennial grass

- Lucerne

NU 0-10 cm

Sep-01 Dec-01 Mar-02 Jun-02 Sep-02 Dec-02 Mar-03 Jun-03 Sep-03 Dec-03

So

il m

ois

ture

(%

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

NU 10-30 cm


0.0

0.1

0.2

0.3

0.4

0.5

0.6

NL 0-10 cm


So

il m

ois

ture

(%

)

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

NL 10-30 cm


0.0

0.1

0.2

0.3

0.4

0.5

0.6

SU 0-10 cm


So

il m

ois

ture

(%

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

SU 10-30 cm


0.0

0.1

0.2

0.3

0.4

0.5

0.6

SL 0-10 cm


So

il m

ois

ture

(%

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

SL 10-30 cm


0.0

0.1

0.2

0.3

0.4

0.5

0.6

NU 0-10 cm


So

il m

ois

ture

(%

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

NU 10-30 cm


0.0

0.1

0.2

0.3

0.4

0.5

0.6

NL 0-10 cm


So

il m

ois

ture

(%

)

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

NL 10-30 cm


0.0

0.1

0.2

0.3

0.4

0.5

0.6

SU 0-10 cm


So

il m

ois

ture

(%

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

SU 10-30 cm


0.0

0.1

0.2

0.3

0.4

0.5

0.6

SL 0-10 cm


So

il m

ois

ture

(%

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

SL 10-30 cm


0.0

0.1

0.2

0.3

0.4

0.5

0.6

Source: Hackney (2009)


pastures – method of introduction

• How are you going to introduce new species?

- Surface broadcast

- Disturbance

- +/- retard existing pasture?

- Rate – more later

Source: Dowling et al. (1971)

Sowing new pastures

Weed seed bank-annual grasses

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3

% v

iab

le s

ee

d

Years

Annual ryegrass

Barley grass

Vulpia

Wild oats

Sources: Dowling et al (1991); Peltzer and Mason (1999);

Weed seed bank – perennial grass weeds

Sources: Gardener et al. (2003); Lamoureaux et al. (2006), Maze et al. (1993)

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 5 12

% v

iab

le s

ee

d

Years

Chilean needle grass

Serrated tussock

African lovegrass

Weed seed bank – broadleaves

Sources: Cheam (1987); Dunbabbin and Cocks (1999); Peltzer and Mason (1999); Green et al. (2010)

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4

% v

iab

le s

ee

d

Years

Wild radish

Fleabane

Spiny emex

Capeweed 1

Capeweed 2

Remember…………..

•No herbicides to selectively remove annual grass weeds from perennial grasses in the year of establishment

•Get broadleaves under control ahead of time so use only ‘soft’ options in first year to maximise seed set

Species choice – tolerance to limitations

•It’s about what you can grow given the limitations of paddock….not necessarily

what you want to grow.

•Think about:

- Soil physical conditions (depth, WHC, dispersion, waterlogging)

- Soil chemical conditions (pH, pH at depth, P, S……)

- Aspect, slope

=

Legume tolerances and characteristics

Rainfall (mm)

pHCa Waterlogging tolerance

Hardseed (%)

RLEM tolerance

Native bud worm tolerance

Maturity (flowering)

Bloat risk

Subclover >350 4.5-8.0 sub-poor brachy- poor yann - good

Most <25 Most <25 Most <40

No Yes 85-160 High

Lucerne >375 5.0-7.5 Poor No Yes High

Bladder clover

>350 5.0-8.0 Poor 50-60 No Yes 110-120 High

Gland clover

>350 4.5-8.0 High 40-50 Yes Yes 100-120 High

Arrowleaf clover

>400 4.5-7.5 Poor 40-50 No Yes 130-180 Moderate-high

Balansa clover

>350 4.8-8.0 Very high Variable No Yes 95-130 High

French serradella

>325 4.0-7.5 Poor 0-50 No No 90-130 Nil

Yellow serradella

>300 4.0-7.5 Poor 60-95 No Moderate 95-140 Nil

Biserrula >325 4.2-7.0 Poor 70-90 No Yes 110-135 Low??

Sulla >400 5.5-8.5 Poor Low No Yes ~120 Nil

Hardseededness and maturity time - legumes

•Hardseededness comes into play after the first year of

seed set - Bought seed is generally scarified

- Hard seed means the seed has a seed coat that is impermeable

(resistant) to water penetration

- Hard seed break down affected by

- Moisture

-Temperature

- Choose higher hard seed varieties in harsher/more variable

climates

•Maturity time - Refers to time to flowering

- Choose shorter season for harsher/more variable climates

- Caution – getting too extreme in subclover selections

•Serradella and biserrula indeterminant -will flower and

produce seed while moisture available

Indeterminant plants, maturity time

Early spring seeds/m2

Late spring seeds/m2

Total seeds/m2

Biserrula 2715 3258 5973

Gland clover 2046 0 2046

Bladder clover 760 0 760

Subclover 250 0 250

Source: Hackney and Quinn 2016

Choosing mixtures

•Think carefully when choosing mixtures

•With complex mixtures there can be difficultly

in:

- matching herbicides to all pasture components

- grazing to suit persistence needs of pasture components

- maintaining balance – grass/legume ratio

- initial dominant species may initially outcompete and

interfere with establishment of long term persistent

species

- simple is often better

Fertiliser for pasture sowing and maintenance

• Cropping fertilisers (e.g. MAP and DAP) commonly used at pasture establishment

- Contain plenty of N and P………but

- No S

- More than 90% paddocks deficient in S

• Starter fertiliser containing N, P and S for sowing

- seeds only have sufficient N to supply seedlings for 7-10 days

- don’t forget about Mo for legumes in deficient areas

• Maintenance and building fertility

- soil test – P, PBI, S (not accurate for trace elements)

- No production benefit in applying fertiliser above critical levels

0

20

40

60

80

100

% m

axim

um

gro

wth

Available P

Legume inoculation

pH

4.0

pH

4.5

pH

5.0

pH

5.5

pH

6.0

pH

7.0

pH

8.0

Subterranean clover Plant

Rhizobia

Serradella Plant

Rhizobia

Biserrula Plant

Rhizobia

Lucerne, annual medics Plant

Rhizobia

Red = poor , Orange = sub-optimal, Green = optimal

Source: Ron Yates, DAFWA; various

Improving life for rhizobia

• Most rhizobia activity in top 20 cm soil with majority in the top 10 cm

• A relatively small change in pH via liming may induce significant change in nodulation and nitrogen fixation

• Non-legumes without access to nitrogen can’t perform at their best


0

100

200

300

400

500

600

700

800

Unlimed Lime

No

du

le n

um

be

r (n

um

be

r/g

roo

t)

a

b

pH 0-4 cm = 4.2 pH 4-9 cm = 4.0 pH 9-18 cm = 4.17

pH 0-4 cm = 5.6 pH 4-9 cm = 5.7 pH 9-18 cm = 6.0 pH 18-30 cm = 6.2

Richardson et al. (1988)


0

10

20

30

40

50

60

70

80

90

100

0-4cm 4-9cm 9-18cm 18-30cm

Pe

rce

nta

ge o

f n

od

ule

s (%

)

Unlimed

limed

Richardson et al. (1988)

More nodules (previous slide) and distributed through root system


Unkovich et al (1996)

0

10

20

30

40

50

60

70

80

90

pH 4.8 pH 5.1

Nd

fa (

%)

0

10

20

30

40

50

60

70

80

90

pH 4.6 pH 5.6

Nd

fa (

%)


Unkovich et al (1996)

0

10

20

30

40

50

60

70

80

90

pH 4.8 pH 5.1

Nd

fa (

%)

How long do un-protected rhizobia live?

Event

Time Elapsed

(hours)Number & %

Surviving

per seed

At Inoculation (inoculant applied to

seed in a 0.75% methylcellulose slurry)

0 1,445,000 *

(100%)

Lupins mixed in vertical feed mixer

and augered into truck

1 141,200 # (9.8%)

Transported to field and augered into

air seeder box (sampled from seeder

box)

4.75 11,200 # (0.8%)

Planted by air seeder 4.8 6,761 # (0.5%)

Recovered from soil 22.5 1,175 # (0.1%)

* Theoretical number derived from number in inoculant slurry.

# Numbers determined by MPN method.

Reference: Roughley et.al 1993 Soil Biol. Biochem.25:1453-1458.

Preparation – how much seed is in an

old pasture?

What is the weed seed level in a pasture?

Source: Bowcher 2002

Weed seed bank-annual grasses

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3

% v

iab

le s

ee

d

Years

Annual ryegrass

Barley grass

Vulpia

Wild oats

Sources: Dowling et al (1991); Peltzer and Mason (1999);

Preparation – how much seed is in an

old pasture?

What is the weed seed level in a pasture?

Annual grass Broadleaf weed

Continuous grazing 5859 1020

Spring hay cut 668 419

‘Ideal’ clean 59 10

Sources: Dowling et al (1991); Peltzer and Mason (1999); Bowcher (2002)

•Sowing rates compared to weed seed bank are low

• Sub clover sown at 4 kg/ha

– 120 000 seeds/kg x 4kg/ha = 480 000 seeds/ha

= 48 seeds/m2

• Phalaris sown at 3 kg/ha

– 650 000 seeds/kg x 3 kg/ha = 195 seeds/m2

Sowing rate – how much do you use?

Annual grass Broadleaf weed

Continuous grazing 5859 1020

Spring hay cut 668 419

‘Ideal’ clean 59 10

•Options –Stand alone

–Undersowing/cover cropping

–Summer sowing (need unscarified/in-pod seed)

–Twin sowing (need unscarified/in-pod seed)

Sowing technique

Establishment technique and seed yield

-100

0

100

200

300

400

500

600

700

800

Bis

err

ula

Bis

err

ula

CC

Bis

err

ula

TS

Fre

nch

Fre

nch C

C

Fre

nch T

S

Bla

dder

Bla

dder

CC

Bla

dder

TS

Subte

rranean

Subte

rranean C

C

Seed p

roduced (

kg/h

a)

Source: Hackney et al. (2013)

Sowing technique and seed size

0

20

40

60

80

100

Bis

err

ula

Bis

err

ula

CC

Fre

nch

Fre

nch C

C

Bla

dder

Bla

dder

CC

Subte

rranean

Subte

rranean C

C

Rela

tive s

eed s

ize (

%)

Source: Hackney et al. (2013)

•Annual legumes - need to be sown in autumn (preferably early)

- NOT Winter – too cold

- NOT spring – not enough time to set seed

- options now for summer sowing……more later

•Perennial grasses and lucerne - autumn

- late winter/spring

- think about annual companion legumes

- after??

- before??

•Pastures containing perennial grasses will tend to run to grass dominance over time - legume seedbank and management for legume regeneration critical

Sowing time – when do you sow?

Sowing time – when do you sow?

Moot et al. (2000)

Sowing - depth

• Most pasture seed quite small:

• Subclover – 130 000 seeds/kg

• Balansa clover – 1 500 000 seeds/kg

• Lucerne – 500 000 seeds/kg

• Cocksfoot – 1 300 000 seeds/kg

• Phalaris – 650 000 seeds/kg

• Sowing depths > 1 cm can result in significant reduction in emergence

Sowing - scale

• Better to do a small area well than a large area poorly

• Don’t compromise on

- Preparation

- Species/variety choice to suit paddock limitations

- Rate of sowing

- Don’t lower rate to increase area

- Seed nurseries can help get around this

problem

- Timing – if it’s getting too late, don’t do it.

Beware………

Chemical residues

Herbicides

Triasulfuron (LG) application on Sub clover (18 days growth) DAFWA Crop Pasture Group (Yates, Nutt & Loi)

3g 0.3g 0.03g 0.003g 0.0003g control

1/10 1/100 1/1000 1/10000 1/100000 of recommended rate

Triasulfuron (LG) Pyroxasulfone (S) Control Chlorsulfuron (G) Clopyralid (LT)

Source: Ron Yates, DAFWA

Photo: Jo Powells

•Prioritise

•Know paddock limitations and what you can practically and economically do about them

•Manipulation only possible where there are exploitable differences

•If sowing new pasture, select to create exploitable differences

•Choose what you should grow

•Timing, timing, timing……….

Summary

enemies of pasture establishment and legume regeneration ...€¦ · enemies of pasture...

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