Making lime pay: can you get a quicker return?

GRDC western regional panel member Susan Hall

Growers have been busy in recent weeks applying lime to paddocks as part of ongoing efforts to overcome soil acidity and maximise their farm’s potential.

As a Grains Research and Development Corporation (GRDC) western regional panellist, I know farmers are very interested in lime and the best way to apply it.

Lime’s importance in improving soil pH levels is highlighted by the latest Department of Agriculture and Food (DAFWA) estimates showing that soil acidity costs Western Australian growers up to $500 million annually in lost production.

But understandably, getting the best value from their lime investment is a high priority for growers.

There is no doubt that lime can improve yields on acidic soils and is a preventative treatment to maintain soil pH at acceptable levels.

Results from GRDC-supported research conducted by DAFWA and CSIRO reveal that lime application increases medium to long-term yields by an average of 0.25 tonnes per hectare, or 12 per cent.

But lime takes time to react in the soil and significant yield responses in the first two years after application are not usually achieved.

The GRDC is investing in research looking at the interaction of soil pH with nutrient availability.

This includes recent trials, led by DAFWA’s Craig Scanlan, investigating how cultivation and lime change soil nutrient availability.

Dr Scanlan presented findings from these trials to Perth’s 2014 Agribusiness Crop Updates, supported by GRDC and DAFWA.

He found that a quicker ‘payback’ on lime application was possible using incorporation, although the yield benefit was mostly due to the cultivation effect.

2013 trials at Dandaragan and Dalwallinu showed the yield benefit achieved by cultivation alone was enough to offset, in the first year of application, the cost of cultivation and some lime application.

“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.”

Dr Scanlan believes the incorporation of lime using cultivation will also have ongoing benefits because acidic subsoils are likely to be ameliorated at least two or three years faster than if lime was top-dressed.

He says 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 tool mixes to the depth of the pH constraint.

Agribusiness Crop Updates papers about lime and soil acidity are available at www.giwa.org.au/2014-crop-updates.

Meanwhile, a separate GRDC-supported trial hosted by the West Midlands Group tested a range of tillage treatments to incorporate lime in 2013.

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.

GRDC Kwinana East Regional Cropping Solutions Network trials will take place this year looking at the best rates and incorporation methods for lime and gypsum on different soil types in the eastern grainbelt. 

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.

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