South Perth, Western Australia
May 3, 2004
Cadiz
serradella pasture can play an important role in the fight
against herbicide resistant weeds such as wild radish and annual
ryegrass, according to
Western Australia Department of Agriculture pasture
specialist Keith Devenish.
“Cadiz French serradella has been the catalyst in
offering short term pasture phases to bring weed populations
back under control with two main sowing systems evolving”, Mr
Devenish said.
“The major change is the ability for farmers to
grow and harvest their own serradella seed for less than 50
cents a kilogram and being soft seeded, the Cadiz can be
inoculated and sown as a cleaned header sample.”
One system is to dry seed Cadiz pasture early,
followed by grazing with sheep to keep weeds down during the
growing season and then brown manure the whole stand with
glyphosate ready for cropping again.
Mr Devenish said one tool used with this system
was tactical or crash grazing early in the season while feed is
limited and sheep have to eat everything on offer, including the
weeds.
This system suits a one-year pasture phase that
is desiccated at the end of the season so that no weeds set any
seed and the nitrogen breaks down quicker for the next wheat or
canola crop.
The second sowing system is to sow Cadiz for two
years by sowing after the normal cropping program when several
germination’s of weeds can be spayed out and farmers with own
their supply of cheap seed can sow double the normal seeding
rate of Cadiz.
Grazing and spray topping with paraquat are used
in the first year and then glyphosate in the second year to
desiccate and brown out all the weeds in spring.
Mr Devenish warned that a two-year pasture system
does have a risk of failing in the second year with about a 40
per cent chance the Cadiz will have poor regeneration due to
normal weathering of the soft seed.
“This just means growers need to monitor closely
at the start of the second season and be flexible enough to
change plans and sow a grain crop or re-sow the paddock to
Cadiz”, he said.
“On the other hand, I have seen Cadiz germinate
in February after summer rain and be tough enough with its deep
root system to persist much longer than other annual pastures
until normal winter rains, allowing it to grow well into October
and November giving green feed for 10 months,” he said.
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“While ryegrass is reasonably easy to control in
the system, wild radish still causes some issues with about 70
percent of serradella stands having to be sprayed for wild
radish.
“Spray grazing for radish control is a great tool
for sub-clover pasture but is not an option with serradella so
herbicides like Broadstrike, Raptor or Spinnaker have to be
used”.
“Better still are the blanket wiper machines
where high chemical concentrate can be wiped onto wild radish at
less than 50 cents a hectare for herbicide costs and the wiper
equipment can be towed behind a 4WD ute.”
Other non-chemical options such as cutting
serradella hay, mowing and grazing are important and an early
shallow cultivation (tickle) before sowing pasture followed by a
knockdown reduces weed burden considerably.
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A blanket wiper machine is ideal for
targeting taller weeds like wild radish in the fight against
herbicide resistant weeds. |
In one paddock where the farmer had a crop
failure from herbicide resistant ryegrass, he used an early
tickle to encourage the weeds, grazed throughout the first
season with eight sheep per hectare and spray topped paraquat
twice in spring to stop all weeds setting seed.
He then seeded Cadiz in the second year, grazed
with sheep again, desiccated the stand in spring with glyphosate
and then it was successfully sown back to wheat in the third
year used trifluralin to control what ryegrass was left.
My Devenish said the commercial release of two
new hard-seeded French serradellas, Erica and Margurita, offer
some more options and he will be conducting trials with farmers
in Jerramungup and Ravensthorpe to test new ideas.
The recently released farmnote 62/2003
“Serradella – growing and harvesting the seed” explains the
agronomic management and how to harvest several varieties of
serradella seed can be accessed from the Department’s website at
www.agric.wa.gov.au |
