Thinking outside the box on soil acidity
Alternatives to traditional lime products such as finer granulated limes, liquid limes and calcium nitrate as a fertiliser are being investigated as part of research looking at new ways to fast-track production gains from acidic soils.
A five-year project looking at new soil amendment options and tillage tactics for soil acidity is being conducted through the Grains Research and Development Corporation (GRDC) Soil Constraints – West initiative by the Department of Agriculture and Food (DAFWA) and The University of Western Australia (UWA).
DAFWA soil scientist Chris Gazey said that as well as testing alternative lime products, researchers would mix lime with organic substances, such as compost and crop residues, and assess the effects of gypsum and applying silicates (diatomaceous earth) on the soil surface and at depth.
“These treatments will be evaluated in glasshouse trials at UWA and the most promising will be tested at several field trial sites across the grainbelt, along with several soil disturbance treatments,” he said.
“These will include one-way and mouldboard ploughs and modified deep rippers with inclusion plates.”
Mr Gazey said glasshouse and field trial data would be used to assess the costs, crop yield advantages and residual benefits of different soil acidity amelioration options compared with untreated scenarios.
“The aim is to have a good understanding of the effectiveness and economic impact of various treatments over the long term,” he said.
“Meanwhile, the recommendation to growers is to soil test to depth and apply the appropriate rate of best value-for-money lime (lime sand, limestone or dolomite) adjusted for neutralising value and particle size, and to incorporate it whenever possible.”
GRDC Western Regional Panel member Gemma Walker said soil acidity was an important issue for WA growers including those in the Esperance region, where she farmed at Munglinup.
“Depending on farm location and access to quality lime sources, it can cost some WA growers upwards of $50 per tonne to purchase, transport and spread lime, which tends to take at least four to seven years to provide a return on investment when top-dressed at appropriate rates to improve pH sufficiently,” she said.
“Soil acidity and treatment options have been a frequently raised topic by growers consulted with during GRDC Western Regional Panel spring tours and other events.
“DAFWA estimates that more than 70 per cent of surface soils and half of subsoils across the WA grainbelt – about 14 million hectares – are affected by soil acidity that can reduce wheat yields by up to 13 per cent.”
Ms Walker said a recent GRDC-funded economic analysis of the impact and management of subsoil constraints in WA, conducted by DAFWA economist Elizabeth Peterson, found that subsoil acidity had the highest cost in lost production in average terms ($141/ha per year) and in total terms ($1.6 billion/year) compared with subsoil compaction and sodicity.
“The analysis assumed that only one constraint was acting at a time. In reality, these constraints rarely exist in isolation and the next phase of Soil Constraints – West will focus on how they interact and the amelioration of multiple constraints,” she said.
Ms Walker said Dr Peterson’s analysis also showed that liming to ameliorate soil acidity increased the indicative equivalent annual profit by $63/ha per year – with $11 returned for every $1 invested.
Gemma Walker, GRDC Western Regional Panel
0428 751 095
Chris Gazey, DAFWA
08 9690 2000, 0429 107 976
ContactNatalie Lee, Cox Inall Communications
08 9864 2034, 0427 189 827
GRDC Project Code DAW00252, DAW00236, DAW00238, DAW00242, RSS00010, CWF00019, SFS00026