- Doubling lime rates is helping productivity
- Lime applications can reduce weed burdens in low pH soils
- Top-dressed lime can take three to five years to significantly lift subsurface pH and improve yields
A boost to liming rates may not only help improve soil and boost yields but can also reduce weed burdens in low pH soils
Ryan Forsyth – a strategic increase in lime rates is improving crop health and weed suppression.
PHOTO: Evan Collis
Although applying lime has been a long-held practice for Western Australian grower Ryan Forsyth, who farms 6400ha with his wife Kerry, father Rod and mother Judi, the decision to double the amount applied has been reaping benefits.
Ryan says increasing liming rates on certain paddocks has boosted productivity and profitability. It has allowed for more barley to be planted, which for the Forsyths achieves a better margin than wheat. “Barley doesn’t like low pH soil, which is what we have,” Ryan says. “It normally sits at 4.5 to 5.5. Liming improves our soil’s pH level.”
Ryan says he used to lime at a rate of one tonne per hectare but this has been increased to 2 to 2.5t/ha during the past five years. A healthier crop has reduced competition from weeds, in turn helping boost yields.
The Forsyths’ experience echoes results from GRDC-funded trials between 2010 and 2014 at Merredin, Wongan Hills and Eradu.
Farm manager: Ryan Forsyth
Location: Kellerberrin, Western Australia (205 kilometres east of Perth)
Farm size: 6400 hectares, with 1000ha of native bush
Average rainfall: 330 millimetres, 225mm in winter
Soil types: deep sand over clay
Enterprises: cropping and Poll Merinos
Ideal crop rotation: wheat/canola/barley/lupins
Crop program (2015): wheat 4000ha, barley 500ha, canola 970ha, lupins 200ha
The research – by the Department of Agriculture and Food, Western Australia (DAFWA), the Australian Herbicide Resistance Initiative and the University of Western Australia – found that lime applications reduced weed burdens in low pH soils. As topsoil and subsoil pH levels rose in the four to five years after application, crop competition increased and herbicide efficacy improved.
The trials found that using lime to achieve even small increases in pH significantly reduced the density of annual ryegrass, barley grass and wild radish in the four-year timeframe.
Despite subsurface pH levels rising only marginally in the four-year period and not reaching the recommended pH of 4.8 for optimal crop root growth, yields for wheat, barley and lupins increased by an average of six to seven per cent (at two sites) where lime was applied.
DAFWA’s principal weed science research officer Dr Abul Hashem says in 2013 barley yields were up to 138 per cent higher where lime and herbicides were used, compared with the untreated control. Trial results also reinforced the message that lime takes some time to move down the soil profile to alleviate acidity, but can have a positive effect on lowering weed burdens within four to five years.
“Growers with a high weed burden in acid soils should consider applying lime at rates of 2.5t/ha or higher as another tool to reduce the impact of wild radish and annual ryegrass, as well as getting other benefits of the lime,” Dr Hashem says.
Although Ryan is happy with his new liming strategy, he laments the time it takes for an initial application to work. “We often don’t see a benefit for two to three years.”
Long-term WA trial data show top-dressed lime that increases the surface pH to above 5.5 can take three to five years to significantly lift subsurface pH below 10 centimetres (longer for below 20cm) and improve crop yields.
Ryan says research on speeding up lime’s activity would be a priority. “Rain would also help in getting the lime through the soil profile.”
The Forsyths’ farm at Kellerberrin in Kwinana East Port Zone receives about 330 millimetres of rain annually, with about 225mm falling in winter. This season has seen some “good rain”, Ryan says, with six-week breaks between falls. “The place is looking good.”
The majority of the farm is deep sand over clay and has been soil tested. It has meant that the Forsyths have been able to increase lime applications (applied using variable rate technology) at the expense of phosphorus. “We have dropped our phosphorus rates down but we’ll need to watch this so we don’t deplete what we have.”
As well as cropping, the Forsyths run sheep. Poll Merinos make up 10 per cent of their enterprise and are managed by Ryan’s father, Rod. In a bid to better integrate them into the overall enterprise, the Forsyths took part in a GRDC-funded Grain and Graze 2 trial in 2011 and 2012.
Liming in WA
The Department of Agriculture and Food, Western Australia (DAFWA), estimates that about 14.25 million hectares of the state’s wheatbelt soils are acidic, or at risk of becoming acidic, to the point of restricting crop yields.
In 2013, DAFWA estimated that WA growers apply about one million tonnes of lime annually. However, it wants this level increased to 2.5 million tonnes annually to address acidification and to recover pH to levels where cereal yields are not constrained.
The crop grazing trial sought to determine the impact of grazing winter crops on subsequent grain yield and quality, on weeds, disease and nutrition and on livestock carrying capacity.
The trials showed it was possible to graze crops in winter and still maintain grain yield, although there were more frequent yield penalties during the drier 2012 season than the 2011 season.
For the Forsyths’ crops, the yield penalty was 15 per cent on wheat in 2012 when the crop was heavily grazed from early to mid-July. With less rain than the 2011 season, moisture stress could have reduced the ability of crops to recover from grazing, exacerbating the negative effects of late and heavy grazing.
Ryan says the trial was beneficial, even though it has not changed any on-farm practices. “We did the trials and seemed to get the same results and now we’re keen to try something else.”
He says they have “struggled” to fit sheep in, with compaction an issue. “A lack of rain at the start of the season has meant sheep-grazed paddocks just can’t get established. It’s just too much compaction for the crop to get up and germinating compared to other paddocks. We had 13mm of good rain in May and on those grazed paddocks it just ran off.”
Being involved in locally focused research as well as drawing on broader grains research are important to the enterprise. The Forsyths are part of their local Regional Cropping Solutions Network (RCSN) research group for Kwinana East. (The GRDC-funded initiative aims to provide on-ground links between growers, farming systems groups, agribusiness and researchers.)
Although not involved in any trials now, the Forsyths’ local RCSN group has recently prioritised its research requirements: water-use efficiency, inputs, rotations, rainfall variability and climate, and weeds.
Ryan says dealing with seasonal and price variability is important. “Dad thinks both the seasons and yields are more variable than they have been in the past. We can get a variation of 1 to 1.5 tonnes a year in the same crop. It makes it hard to make marketing and other business decisions and it is purely to do with rainfall. And the thing is, you can get 25mm of rain, and then everything is back on track.”
For Ryan, it is this variability that motivates him: “Trying to achieve as much as we can off a finite resource – water – is something that I can’t control but it motivates me to try to.”
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