KEY POINTS | SOIL PREPARATION | STUBBLE | WEED CONTROL | CARRYOVER
PESTS | CARRYOVER DISEASES
WESTERN
JUNE 2018
SECTION 3
PADDOCK PREPARATION
VETCH
1 paddock preparation
Section 3 VETCH
June 2018
paddock preparation
key points
• Sowing into paddocks with low broadleaf weed infestations is important, as
vetch is a poor early competitor against weeds.
• use integrated pest, disease and weed-management practices.
• control the weed and volunteer ‘green bridge’ before seeding to minimise
disease and pest carryover.
• remediate soil constraints during the summer fallow period.
2 paddock preparation
Section 3 VETCH
June 2018
The approach to paddock preparation and sowing vetch is essentially the
same as for other legume crops. However, as vetch is a poor competitor at
emergence it is especially important to pay attention to detail at this stage
to help ensure maximum production potential.
Vetch is a poor competitor at emergence so ensuring good paddock preparation
maximises crop establishment.
3.1 Soil preparation
Testing for soil limitations and remediation should occur in the summer or autumn
prior to sowing vetch.
3.1.1 Soil pH
While vetch is more tolerant of acid soils than most grain legumes it still prefers soil
pH (CaCl
2) to be >5. Good yields have been grown in paddocks with pH as low as 4.5
(CaCl
2), where aluminium and manganese levels were low.
On soils with a pH
2) nodulation and consequently nitrogen fixation
will be poor. Root growth may also be reduced in acid soils and soils with
subsoil compaction.
Low pH can be remediated with an application of lime during the summer or autumn
period, prior to seeding.
3.1.2 Hard setting and compaction
Both of these soil conditions can reduce root growth and free drainage, limiting
vetch production.
Hard setting and surface crusting are often linked to sodicity. Exchangeable sodium
percentage (ESP) is the measure for sodicity and soils with an ESP greater than six
are considered sodic. Sodicity can generally be improved by the addition of gypsum.
Deep tillage and ripping are used to amend soil compaction and may also be used to
achieve deeper incorporation of lime, gypsum and organic matter.
Implementing a controlled-traffic system after ripping can help minimise recompaction
across a paddock.
1
1 S Davies, T Overheu (2015), Management of dispersive (sodic) soils e\
xperiencing waterlogging Department of Agriculture and Food
Western Australia, https://www.agric.wa.gov.au/sites/gateway/files/CU2013%20EOI%205%20-%20Paul%20Blackwell%20CSPB.doc
IN FOCUS i MORE INFORMATION
Mingenew–irwin Group Soil acidity
management and lime calculator,
http://www.mig.org.au/lime-calculator
For details on soil acidity and liming,
see the following article by Brett
Upjohn, Greg Fenton & Mark conyers
– ‘Management of dispersive (sodic)
soils experiencning waterlogging’,
Agfact A c. 19, 3rd edition 2005,
https://www.agric.wa.gov.au/
water-erosion/management-
dispersive-sodic-soils-experiencing-
waterlogging
▶ VIDEO
on-farm story variable rate gypsum
https://youtu.be/1RWi8KGqPte
▶
3 paddock preparation
Section 3 VETCH
June 2018
3.1.3 non-wetting
In non-wetting soil, crop establishment can be improved with the use of sowing
adjacent to last year’s stubble row, soil-wetting agents, soil disturbance and the
use of press-wheels. If non-wetting soil is severe, addition of clay is worthwhile if
a suitable clay source is available.
In non-wetting soil, delaying sowing until the soil has become wet may be the best
option. Dry sowing with seed furrows left to trap water may not work as furrows may
become filled with soil before germinating rains occur.
3.2 Stubble
The surface retention of cereal stubble does not affect vetch germination or growth
and may improve establishment on hard-setting, surface-crusting soils. It is important
to keep adequate plant residues on the surface to protect the soil from moisture loss
and erosion during establishment, growth and after harvest.
Standing stubble of the previous crop can also help create a trellis for vetch.
However, in hay crops, this standing stubble can be included in the baled material
and can reduce hay quality.
Infected stubble of host crops can be an important source of the disease\
s Aschochyta
blight, Botrytis grey mould, chocolate spot and rust (see Section 2.3.1 Disease).
3.3 Weed control
Controlling weeds and volunteers as early as possible will help conserve soil
moisture, reduce potential disease carryover and minimise blockages at seeding.
Removal of weeds is important as vetch is a poor competitor at emergence and in-
crop herbicide options are extremely limited.
3.3.1 Summer weed control
As a result of an increase in the use of no-till cropping and the incidence of summer
weeds many growers have adopted a spray-fallow system, which predominantly uses
glyphosate over summer to remove weeds and conserve moisture for the next crop.
To reduce the risk of glyphosate resistance developing in fallow weeds some
growers are using weed-detecting technology (WeedSeeker®, WEEDit) to detect
individual weeds that have survived the glyphosate application and spraying these
with an alternative knockdown herbicide.
Weed-detecting technology uses optical sensors to turn on spray nozzles only when
green weeds are detected, greatly reducing total herbicide use per hectare. The
units have their own light source so can be used day or night. Moving from a blanket
to a targeted application enables a higher herbicide rate per plant to be applied but,
generally, much less herbicide per hectare.
The new technology also has the potential to map troublesome weed patches so that
these areas can be targeted with a pre-emergent herbicide before sowing.
The use of selective grass herbicides and higher rates of paraquat and diquat
(bipyridyl herbicides, Group L) are covered by a permit (PER11163), \
which is in force
until 28 February 2019 and is for all Australian states.
This permit allows the use of about 30 different herbicides from seven different
mode-of-action groups. Additional modes of action are likely to be added to the
permit over time.
Some herbicide rates have been increased to enable control of larger or stressed
weeds. For example, glyphosate (450 grams of glyphosate per litre) rates range from
3–4 L/ha (using a set water rate of 100 L/ha), which far exceeds the label blanket rates
of 0.4–2.4 L/ha. Similar increases in rate have also been permitted for paraquat (e.g,
Gramoxone®).
i MORE INFORMATION
GroundCover tM, ‘Seeding non wetting
soils’, https://grdc.com.au/resources-
and-publications/groundcover/
ground-cover-issue-107-novdec-2013/
smart-new-way-to-place-seed-over-
moisture
GRDc podcast, Sowing sandy soils
https://grdc.com.au/~/media/Audio/
GRDc-Radio-South/120-south.mp3
i MORE INFORMATION
GroundCover tM tV, ‘Stubble height
and crop emergence’
https://grdc.com.au/Media-centre/
Groundcover-tV/2015/01/GctV15/
XD tSbGcZxpM
i MORE INFORMATION
Australian Pesticides and Veterinary
Medicines Authroity,
https://apvma.gov.au/
GRDc Fact sheet – Green bridge
www.grdc.com.au/GRDc-FS-
GreenBridge
GRDc Web resource integrated Weed
Management Hub
https://grdc.com.au/Resources/
iWMhub
Web resource or app HerbiGuide
chemical labels
http://www.herbiguide.com.au/
4 paddock preparation
Section 3 VETCH
June 2018
3.3.2 removing the ‘green bridge’
Vetch should be sown into a clean seedbed, with weeds and volunteers controlled
with cultivation and/or herbicides prior to planting. If not achieved ea\
rlier, paddocks
should be free of weeds for 2–3 weeks prior to seeding to prevent pest and
disease carryover.
2
Left uncontrolled, volunteers (see Section 2, Table 2) and weeds can result in the
carryover of pests and diseases to the vetch crop.
A wide range of products are registered for controlling weeds in fallows. These
including mixtures of paraquat (Group L) and diquat (Group L) and 2,4-D (Group I) and
glyphosate (Group M).
Check plant-back periods before sowing vetch. For example, there is a 7–10 day
plant-back period constraint before planting vetch following an application of
2,4-D (Group I).
There are no pre-planting residual herbicides registered for use with vetch crops
in New South Wales or Queensland. Some formulations of trifluralin (Group D) are
registered for pre-planting use in vetch crops in SA and WA, but not in NSW or
Queensland.
3
Self-sown vetch can itself become a ‘green bridge’ for pests and disease in the
following season. Volunteer vetch seedlings need to be controlled early to minimise
the effects of aphids, viruses and diseases in other pulse crops.
photo 1: Vetch is a poor competitor at emergence and in-crop herbicide options
are limited, especially for broadleaf weeds. Controlling summer weeds and the
‘green bridge’ to minimise pest and disease carryover are essential tools in the
successful production of vetch.
Photo: Emma Leonard, AgriKnowHow
2 GRDC (2012) Green Bridge Fact Sheet. GRDC www.grdc.com.au/GRDC-FS-GreenBridge
3 G Charles (2006) Managing weeds in vetch rotation crops. WEEDpak NSW D\
epartment of Primary Industries
http://www.insidecotton.com/xmlui/bitstream/handle/1/995/WeP%20I3%20Vet…
5 paddock preparation
Section 3 VETCH
June 2018
3.4 carryover pests
Carryover pests to considerer are mites, including balaustium and redlegged
earth mite, aphids and lucerne flea. Removal of the green bridge will reduce the
infestations of establishment pests in vetch and is an important part of integrated pest
management (IPM) (Table 1).
table 1: Best-bet IPM strategy, establishment to maturity. i MORE INFORMATION
timerite
www.timerite.com.au
p ost harvest pre-sowing
Earth mites and
lucerne flea Assess risk.
High risk when:
• history of high mite pressure
• pasture rotating into crop
•
susceptible crop being planted (e.g. canola, pasture,
lucerne, vetch)
• seasonal forecast is for dry or cool, wet conditions
that slow crop growth
If risk is high:
• ensure accurate identification
• use Timerite® (redlegged earth mites only)
• heavily graze pastures in early-mid spring If high risk:
•
use an insecticide seed dressing which is compatible
with rhizobia inoculum on susceptible crops (See
Section 4.4)
• monitor more frequently until crop establishment
• use higher sowing rate to compensate for seedling
loss
• consider scheduling a post-emergent insecticide
treatment.
• earlier sowing into warm soil to give quick
emergence and more vigorous seedlings
If low risk:
• avoid insecticide seed dressings
• monitor until crop establishment
Slugs and snails Assess risk.
High risk when:
• high stubble load
• annual average rainfall >450 mm
• history of slug infestations
• canola being planted
• summer rainfall
• heavy clay soils If high risk:
• burn stubbles
• cultivate worst areas
•
remove weeds in paddocks/along fencelines,
at least eight weeks prior to sowing
• deploy shelter traps prior to sowing
• sow early to get crop established prior to cold
conditions
• use soil compaction at sowing (e.g. press wheels)
• bait at or after sowing prior to emergence
Aphids – virus
transmission Control green bridge (in fallows)
Sow virus-free seed
Sowing into standing stubble may reduce aphid
landing. Assess risk of aphid outbreak.
High risk when:
• warm, mild conditions
• abundant weed hosts
• nearby food sources e.g. clover/medic
Aim to close canopy and minimise gaps
to outcompete infected plants.
Aphids – direct
damage Remove green bridge (aphid hosts) to minimise build
up during autumn and spring.
Sowing into standing stubble may reduce aphid
landing and delay aphid build up in crops. • Control in-crop weeds to minimise sources of aphids
•
Beneficial insects suppress low populations and
reduce the chance of outbreaks.
• High nitrogen may make the crop more attractive
to aphids.
Source: IPM Guidelines for Grains (2013) http://ipmguidelinesforgrains.com.au/workshops/resources
6 paddock preparation
Section 3 VETCH
June 2018
3.5 carryover diseases
Carryover diseases on vetch volunteers include rust and viruses. Other diseases
are carried over on stubble and in the soil and these will not be controlled by green
bridge management (see Table 2 and Section 2, Table 3). More detail on disease
control is in Section 7 In-crop management − disease .
t able 2: Infection sources for major vetch disease.
— Nil * Minor ** Moderate ••• Major
Source: PIRSA/GRDC (2010) Vetch: The Ute Guide – https://grdc.com.au/vetch-the-ute-guide
i MORE INFORMATION
GRDc tips and tactics – Rhizoctonia
http://www.grdc.com.au/tt -
Rhizoctonia
PestFax Map
https://www.agric.wa.gov.au/
diseases/pestfax-map
disease StubbleSeed Soilaphids Volunteer
seedlings
Ascochyta blight *****–– **
Botrytis grey mould **––– **
Chocolate spot ******* – **
Rust **_ *– ***
Seed-borne viruses –** –*** ***
Non-seed-borne
viruses –
––*** ***
