Australian farmers are advised that permanent cover is the way to
overcome the no-till plateau, reports Brendon Cant
Too much bare soil spoilt Rolf Derpsch"s view when he was travelling
3700 kilometres along WA roads earlier this year as part of his six-week
tour of WA and SA.
Hosted by the WA No-till Farmers Association (WANTFA), with support from
the GRDC and the Australian Government"s National Landcare Sustainable
Industries Initiative, the world-renowned Paraguayan no-till expert met
with growers, researchers and agribusiness to analyse Australian no-till
"Australian growers have reached a plateau in terms of no-till and
won"t enjoy maximum benefits until their soil is permanently covered,"
Mr Derpsch said. "Carbon content is the most important parameter
determining soil quality as it alleviates structural, nonwetting and nutrient
"To substantially increase carbon content, baling and burning of
stubble must be abandoned and sheep locked out of cropping paddocks."
In 20 years of no-till, Brazil"s soybean yields increased 50 per cent,
while fertiliser use halved. Meanwhile, corn yields doubled and 30 per
cent less fertiliser was applied.
"To reach full sustainability, at least three tonnes of stubble
per hectare is required," Mr Derpsch said. "This is achieved
by including cover crops, changing from tynes to discs and diversifying
rotations. Continuous soil cover keeps soil temperatures below 35 degrees
Celsius, ensuring improved microbial activity and better nutrient cycling."
At the GRDC-funded Meckering site, WaNTFA trialled suitable cover crops,
such as annual legumes, and pastures, brassicas, grasses and broadleafs,
such as sunflowers, for inclusion in wheatbelt rotations.
WANTFA"s scientific officer, Dr Ken Flower, says sowing time is a key
factor in how well cover crops produce biomass and control weeds. "Saia
oats (Avena strigosa), Oriental mustard (Brassica juncea)
and French serradella showed good potential in our 2005 trials. Cover
crops, such as Saia oats, produce a large amount of residue.
"Bill Porter, Department of Agriculture, is running trials at Meckering
testing Saia oats" ability to accelerate liming movement down the soil
At WaNTFA"s 2005 Meckering Spring Field Day, Mr Derpsch explained how
Brazilian growers used a double disc system, with 34-centimetre (15-inch)
front and 29cm (13-inch) back discs rotating at different speeds to self-clean.
"The front wheel"s weight cuts through residue, the second wheel
furrows and the rear rubber press-wheel closes," he said. "Planting
east-west decreases weed biomass, as shading by the crop occurs."
Disc benefits, such as a 14kmh working speed, halving fuel costs, reducing
weeds and better handling of high residues, were highlighted by a five-grower
panel at the field day.
Mr Derpsch and DR Flower visited the south coast of Wa, where growers
have seen Rhizoctonia in canola and take-all in wheat disappear and yields
increase by between 50 to 100 per cent since they adopted no-till in 1996.
Mr Derpsch reported that soil could not be seen through the residue and
increased organic matter had reduced nonwetting soils in all crops, except
They also visited Jim and Chris Kirkwood"s property at Kendenup, Wa,
and saw discs successfully used in stony paddocks, after raking and removing
large stones. Chris Kirkwood said: "I plan to use soft-seeded oil
radish to aerate soil and introduce more oilseeds and cover crops in shallow
clay areas to increase soil aeration."
Mr Derpsch explained that plants biologically prepare soil by loosening
it with their roots, forming pathways for the next crop. "We"ve used
blue, yellow and white bitter lupins successfully in South America, as
they can have 1.2 metre-long roots and alkaloids in their leaves prevent
DR Flower concluded that conditions in WA were unique. However, by investigating
no-till techniques around the world, WA growers and researchers could
learn and adapt, progress to more sustainable no-till and enjoy greater
Dr Bill Porter talks to growers about the potential of Saia oats as
a liming accelerant at the recent Meckering Spring Field Day. Photo: Brendon
Cover-crop trials at the GRDC-supported WaNTFA site at Meckering. Photo:
GRDC Research Code WaN00003
For more information: DR Ken Flower, 08 9622 5584, 0427 000 729
North, South, West