Condamine growers, Rodney (left) and Sam Hamilton,
are looking to the results of strategic tillage trials on
their property for a cost-effective alternative to
On-farm trials are revealing to southern Queensland grower Rodney Hamilton that a strategic approach to cultivation for weed control may be a profitable option on his family’s Condamine property, which is otherwise a no-till operation.
When the Hamiltons – Rodney and his son Sam – started hosting the trials on their 4046-hectare property in 2012, they were sceptical that ploughing the soil would not undermine the long-term benefits of no-till, which have seen increased yields and a lift in overall profitability.
However, the GRDC-funded research led by Dr Yash Dang, from the Queensland Department of Science, Information Technology, Innovation and the Arts (DSITIA), has indicated that occasional cultivation has the potential to increase both yields and gross margins, while retaining soil health.
As part of the trials, the Hamiltons used a chisel plough to cultivate the soil to a depth of 20 centimetres, mostly to control feathertop Rhodes grass, on 6 March and 18 April in 2012.
PBA HatTrick chickpeas were then sown on the trial plot, which received two herbicide sprays during the growing season as did the surrounding pulse crop. About two-thirds of the family’s chickpeas were also spot-sprayed, but this was not required on the cultivated plots due to low weed pressure.
In establishing the trials, Rodney’s main concern was maintaining the soil health benefits that no-till has accumulated over 20 years in his farming system, such as high levels of microbial activity, erosion control, better soil moisture retention and, ultimately, yield gains.
But he was also curious about whether cultivation might help mitigate the costly side effects of no-till principles, such as high weed pressure, particularly following wet seasonal conditions.
A recent survey of 55 growers and advisers in the northern grain-growing region showed that no-till systems have higher weed and disease pressure than farming systems where tillage is used.
Results from the first year of the trials showed that one pass of the chisel plough across the Hamiltons’ paddock had increased their chickpea yield by almost 0.1 tonnes per hectare. After two cultivations, the yield still increased, although only by 0.02t/ha.
In combination with high chickpea prices, at $550/t in 2012, the yield gains saw their cultivated chickpea plots return an extra $32/ha after one tillage, and $31/ha after the second tillage. In other words, cultivating before sowing chickpeas could potentially see their 1300ha pulse crop return an extra $41,600.
Of the five properties across the northern grains region where strategic tillage trials were conducted in 2012, cultivation was shown to be the most profitable on the Hamilton farm. This was an important finding for Rodney, who pushed for profitability to be added to the criteria for evaluating the results.
Net returns per hectare for wheat and barley ranged from $2.50/ha to $22.60/ha in the other on-farm trials at Biloela, Moonie and Hermitage in Queensland and Wee Waa in northern New South Wales.
A clod of earth showing an
earthworm tunnel points to the high levels of
microbial activity – achieved through long-term
no-till practices – that the Hamilton family is
keen to preserve on their property.n underneath
PHOTOS: Clarisa Collis
The gains are thought to stem mainly from the reduced weed pressure resulting from tillage. Rodney says feathertop Rhodes grass, followed by herbicide-resistant barnyard grass and fleabane are the main weeds on his family’s property.
Researchers found a single cultivation had decreased the number of weeds by more than 50 per cent on all the trial plots.
On the Hamiltons’ property, the average number of weeds declined from 14 plants per square metre to six plants/m2 after the first cultivation. But after the second tillage, the number of weeds in their chickpeas had decreased to just 2.2 plants/m2.
However, Rodney says this is unlikely to result in herbicide cost savings because he has found that there is only a small cost difference between boom spraying and using WeedSeeker® technology to selectively spray a large crop area.
The research indicates the on-farm cost of cultivation is about $10/ha, while the contractor cost is approximately $15/ha. However, Rodney estimates that it would cost a minimum of $20/ha and up to $32/ha for a one-pass operation over his 4046ha cropping area using his own chisel plough and tractor.
He says this figure includes the on-farm costs of 41 tynes at $40 each, which generally need replacing after ploughing about 1300ha, plus fuel and labour costs and the increased rate of machinery depreciation likely to result from cultivation.
Overall, it would cost the Hamiltons a total of $81,000 to cultivate their entire crop area once, using Rodney’s cost estimate of $20/ha.
However, this expenditure may be offset by the increased profitability resulting from tillage, given the 2012 trials showed a return of an extra $41,600 for their chickpeas alone.
While the preliminary findings are encouraging, Rodney is waiting to see the results from the on-farm trials in 2013 and 2014 before deciding whether to till his entire cropping area.
“It will take more than one year of trials to convince me to take up the chisel plough again,” he says. “We need to know how many tillages cause damage and over what period this is likely to occur.”
Despite the potential for strategic tillage to reduce weed pressure, and increase yields and profitability, Rodney’s reluctance to cultivate is largely driven by a strong desire to protect the soil health that supports productivity in his farm business.
This concern was partly vindicated when soil samples collected to a depth of 50cm showed that one tillage resulted in a slight decline in microbial activity. Conversely, two passes of the chisel plough substantially increased microbial activity.
The trials also showed that other indicators of soil health were not significantly affected by tillage, but there were slight decreases in the soil’s bulk density and organic carbon levels. Soil moisture levels were mostly unchanged.
The ongoing research by Queensland DSITIA in partnership with the Queensland Department of Agriculture, Fisheries and Forestry is continuing to examine the effects of strategic tillage this season and aims to determine the optimum time to cultivate.
07 4628 1103, 0428 281 103,
Dr Yash Dang,
07 4529 1245, 0427 602 099,
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