Assessing the impact of lime

Countryman
Assessing the impact of lime
Camera IconAssessing the impact of lime Credit: Countryman

Shifting investment from nutrients to lime incorporation can be profitable on acid soils, and provide immediate benefits, Department of Agriculture and Food research shows.

The research, funded by the Grains Research and Development Corporation (GRDC), will be presented at the Agribusiness Crop Updates in Perth on February 24-25.

Northam-based department research officer Craig Scanlan said the field trials were conducted last year at Dalwallinu and Dandaragan to quantify the effect of cultivation and incorporating lime on soil nutrient availability.

"We aimed to determine whether renovating acid soils with lime incorporation causes an immediate change in grain yield response to fertiliser and to assess the relative impact of cultivation, lime incorporation and reduced fertiliser rates on short-term profitability," Dr Scanlan said.

"The trials had a replicated, strip-plot design with a control (no treatment), cultivation, and combined lime and cultivation treatments.

"At Dalwallinu, the method used for cultivation was a deep-ripper followed by a one-way plough fitted with 65 cm diameter discs while an Imants 37SX rotary spader was used at Dandaragan.

"Prior to cultivation at both sites, 3 t/ha of lime sand, with a neutralising value of 94 per cent, was applied to the combined lime and cultivation treatments."

Dr Scanlan said a key outcome of the research was that one-way plough changed soil pHCa in 0-20 cm while rotary spader changed soil pHCa 0-30 cm.

"The results indicate an immediate payback from lime incorporation, however profit is driven by the cultivation effect," he said.

"Cultivation with and without lime led to significant decreases in soil pH in the surface 10 cm at both sites because more acid soil was bought to the surface by the cultivation.

"However, cultivation with lime caused a significant increase in soil pH at 10-20 cm at Dalwallinu, and 10-30 cm at Dandaragan just 17 weeks after its application.

"There was also a yield response to cultivation at both sites, however the addition of lime did not result in additional grain yield.

"At both sites, the mean yield for the cultivation and lime and cultivation treatments was significantly higher than for the control, and the yield for the nil nutrient treatment was significantly lower than for the all treatments."

Dr Scanlan said the research results suggest that subsidising the cost of lime and cultivation by reducing investment in nutrients and maintaining profit in the first year was a feasible proposition.

"The success of this strategy depends on the severity of soil acidity and existing soil nutrient levels," he said. "The lack of yield response to lime incorporation can be explained by the fact that only a small proportion of soil was ameliorated by the one-way plough at Dalwallinu.

"The rotary spader achieved much better mixing of the lime at Dandaragan but had no impact on growth because soil pH was already above target levels.

"The yield benefit from cultivation at both sites was enough to offset the cost of the cultivation and some of the lime application, and the net margin in the year of application could be improved by reducing fertiliser rates.

"There is likely to be a future economic benefit from lime incorporation because the acidic subsoil will be ameliorated two to three years faster than if the lime was top-dressed and not cultivated.

"The research also demonstrated the implement used to achieve incorporation is important. If it can mix to the depth where the soil pH constraint occurs, an immediate payback on lime and cultivation is possible. If not, 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."

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