Researchers have developed initial parameters to guide Western Australian farmers who may be considering cultivating acidic soils to incorporate lime prior to seeding crops in 2014.
Cultivation to incorporate lime can be more economic than topdressing where:
- Soil pHCa is well below 5.5 in the 0-10cm soil layer and well below 4.8 in the 10-20cm layer;
- Soil fertility is adequate;
- The cultivation implement mixes to the depth of the pH constraint.
Growers have traditionally ‘top-dressed’ lime on the soil surface but can be reluctant to do so, despite long-term yield benefits, because it can take several years for these benefits to be achieved.
New research funded by the Grains Research and Development Corporation (GRDC) and conducted by the Department of Agriculture and Food Western Australia (DAFWA) found a quicker payback was possible using incorporation, although the immediate yield benefit was due largely to the cultivation effect.
DAFWA researcher Craig Scanlan said 2013 trials at Dandaragan and Dalwallinu showed the yield benefit achieved by cultivation was enough to offset, in the first year of application, the cost of cultivation and some lime application.
“The results indicate an immediate payback is possible due to the cultivation effect alone.” he said.
“In the trials we assessed whether investment in fertiliser needs to be cut to achieve a profit from lime incorporation and, overall, the answer was no.
“When we took into account grain yield responses and the costs of fertiliser, lime and incorporation, the gross margin was about the same at no and high rates of fertiliser in cultivated treatments.
“The incorporation of lime using cultivation is also likely to have ongoing benefits because acidic subsoils are likely to be ameliorated at least two or three years faster than if lime was top-dressed.”
DAFWA researcher Craig Scanlan addresses the West Midland Group spring field day.
Dr Scanlan said growers considering reducing fertiliser application and cultivating soils to incorporate lime needed to consider a few factors to assess if it would provide short and long-term economic benefits.
“Firstly, soil pHCa in the 0 to 10cm and 10 to 20cm soil layer needs to be well below the levels of 5.5 and 4.8 respectively to produce a significant yield response,” he said.
“Secondly, growers need to use soil test results to ensure that soil fertility is adequate before considering reducing fertiliser rates because low nutrient subsoil brought to the surface reduces topsoil nutrient levels.
“Finally, the cultivation implement needs to be able to mix to the depth where the soil pH constraint occurs to produce an immediate payback on lime and cultivation.
“If the implement cannot mix to this depth, the benefits from incorporating lime need to be balanced against the cost of the cultivation and the risks to crop emergence and soil erosion posed by cultivation.”
Results from the trial were presented at Perth’s Agribusiness Crop Updates, supported by the GRDC and DAFWA, and are available at www.giwa.org.au/2014-crop-updates.
Meanwhile, a separate GRDC-supported trial hosted by the West Midlands Group, has highlighted the importance of measuring subsoil pH levels and applying sufficient rates of lime to prevent and correct subsoil acidification.
The mouldboard plough in action
The trial, which will continue to be monitored, tested a range of tillage treatments to incorporate lime in 2013 including a scarifier, offset discs, one-way plough, deep ripper, rotary spader, mouldboard plough, and a combined treatment of deep ripping followed by spading.
It found that only deep tillage techniques were likely to incorporate lime into the 20 to 30cm acidic layer and that it is important to understand the depth to which lime needs to be incorporated and which subsoil layers need correction.
The GRDC is increasing its western region investment into soil acidity and compaction, which DAFWA now estimates costs up to $500 million annually in lost production across WA’s grainbelt.
New research in 2014 includes GRDC Kwinana East Regional Cropping Solutions Network trials which aim to determine the best rates and incorporation methods for lime and gypsum on different soil types in the eastern grainbelt.
The RCSN trials will investigate if soil pH and sodicity levels in the region can be improved, at low cost, to improve the long-term profitability of local growers.
More information about lime can be found at www.agric.wa.gov.au/climate-land-water/soils/soil-constraints/soil-acidity
, or www.limewa.com.au
which can be used with the www.soilquality.org.au
online lime comparison calculator.
08 9690 2174
GRDC Project Code
DAW00222, WMG00001, CSA00033, DAW00236
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