Long-term trials highlight lime's importance
By GRDC western regional panel member Susan Hall
Following a steep rise in the amount of lime applied to Western Australian paddocks at the start of this year’s cropping season, lime sales are again expected to be high in 2014-15.
WA growers spread more than 1.6 million tonnes of lime in 2013-14, an increase of almost 50 per cent on the previous year, and are increasingly soil sampling at depth and using split or variable rate applications to better target lime applications.
But scientists such as the Department of Agriculture and Food’s (DAFWA) Chris Gazey say that despite these big steps in the right direction, 2.5 million tonnes annually is needed over the next ten years to treat existing and ongoing soil acidity, which costs WA agriculture more than $500 million per year in lost productivity.
Mr Gazey, who recently completed a Caring for our Country soil acidity research project, says WA soils are continuing to acidify, with mapping of the State’s agricultural soils highlighting the severity and extent of soil acidity, including subsurface acidity.
He is now continuing his research and extension efforts supported by the Grains Research and Development Corporation (GRDC).
Mr Gazey says other evidence supporting the need for sustained efforts to address soil acidity includes re-evaluation of a 1994 trial site in a Mingenew paddock showing that lime rates previously considered adequate do not ameliorate soil pH at depth.
The DAFWA small-plot trial was re-examined in 2013 to investigate the long-term effects of liming.
Researchers found that only those plots that had received a total of 8 tonnes per hectare of lime since 1994 had subsurface pH levels close to the recommended target of 4.8 or higher.
In 1994 these plots were treated with the trial’s highest rate of 4t/ha and an additional 1t/ha per year was applied as part of the grower’s normal paddock operations in 1998, 1999, 2003 and 2012.
Wheat yields were 10 per cent higher where 8t/ha of lime was applied since 1994 compared with plots that received a total of 4t/ha of lime in that period.
But that 8t/ha exceeds the amount of lime that virtually all WA paddocks would have received in this timeframe.
The need for a continued focus on liming is also demonstrated by analysis of more than 69 long-term lime trials in WA, demonstrating that long-term yield responses of 10 per cent greater yield are common in years following lime application.
When the analysis removed the year that the lime was applied and the following year (lime takes time to react in the soil and responses in the first two years are not expected) there was an average 0.25t/ha or 12 per cent yield increase.
With the GRDC’s support, Mr Gazey and his colleagues are working closely with WA grower groups to test and improve a range of tools and practices to help growers better manage soil acidity.
The soil acidity research is part of a collaborative research effort ‘Soils Constraints West’ which aims to develop and deliver solutions for a range of soil constraints limiting productive grain cropping in WA.
Soils Constraints West represents more than $33 million of new research aimed at addressing non-wetting soils, subsoil constraints, soil compaction and soil acidity over five years.
The GRDC, DAFWA, CSIRO and Murdoch University are funding the research, which was developed following consultation with WA grain growers through the GRDC western regional panel and Regional Cropping Solutions Networks (RCSNs).
This new research is in addition to the GRDC’s already substantial western region investment in other areas of soil research including soil nutrition, soil carbon and soil ‘health’.
More information about soil acidity and lime is available at the GRDC Soil Acidity in WA Hot Topic at www.grdc.com.au/SoilAcidityWA or on DAFWA’s soil acidity webpages at
Caption: GRDC western regional panellist Susan Hall says GRDC-supported soil acidity research in WA is part of the collaborative research effort ‘Soils Constraints West’.
Susan Hall, GRDC western panel
0400 889 036
Chris Gazey, DAFWA
(08) 9690 2000, 0429 107 976
Natalie Lee, Cox Inall Communications
08 9864 2034, 0427 189 827