Research has revealed that many Western Australian grain growers may be unwittingly sowing break crops into paddocks with subsurface acidity levels that will limit the productivity of these crops.
It has highlighted the importance of growers measuring subsurface, as well as surface pH levels, to prevent break crops being seeded into unsuitable soils.
Break crops such as canola, field peas and chickpeas are particularly susceptible to low pH or aluminium toxicity (which is exacerbated by soil acidity).
The Putting the Focus on Profitable Break Crops and Pasture Sequences in WA project, funded by the Grains Research and Development Corporation (GRDC), has found that one in five WA canola paddocks with adequate surface pH levels will nevertheless have yields limited by poor subsurface pH levels.
Also known as Focus Paddocks, the Department of Agriculture and Food (DAFWA)-led project has aimed to deepen knowledge about the effects of crop and pasture rotations on the farming system, by collecting data from the same 184 paddocks for five consecutive years.
According to researcher Wayne Parker, of DAFWA, only 15 per cent of the canola paddocks tested had an adequate surface pH of 5.5 or greater, and of these paddocks, one in five had a pH less than 4.8 at 10 to 30cm below the soil surface.
He says many paddocks sown to other break crops are also likely to have pH levels that limit crop yields.
Soil pH targets, as established by DAFWA and industry, are set at minimum of 5.5 in the topsoil and a minimum of 4.8 in the subsurface soil.
Mr Parker says it is probable that many growers are unknowingly sowing break crops in paddocks with an unmeasured subsurface pH that is below critical levels, limiting the yield potential of these crops.
Since the late 1990s, the area sown in WA to break crops, particularly chickpea and field pea, has steadily declined, with diseases, weeds and crop architecture often being blamed.
However, Mr Parker believes subsurface acidity may be a significant factor contributing to the reduced popularity of some break crops.
This is because poor soil pH is known to decrease a crop’s competitive ability against weeds, increase disease susceptibility and decrease yield.
Soil acidity is estimated to cost WA agriculture more than $500 million per year in lost productivity.
More information about research into break crops and rotations can be found at the GRDC Break Crop Research Hot Topic at www.grdc.com.au/BreakCropResearch-West.
Soil acidity information can be found at www.grdc.com.au/SoilAcidityWA or www.agric.wa.gov.au/soil-acidity/managing-soil-acidity.
Wayne Parker, DAFWA
08 9956 8555
Paul Kelly, GRDC western panel
0427 275 022
Natalie Lee, Cox Inall Communications
08 9864 2034, 0427 189 827
GRDC Project Code