Comparison of tillage methods for lime incorporation, West Binnu 2016 trial report

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Using tillage to incorporate lime improves the rates of reaction and increases subsurface pH sooner than spreading lime on the surface alone.

Background

Until recently the most common rate of agricultural lime application is one tonne per hectare as a blanket application across the surface of the whole paddock (Taking soil acidity seriously - results of grower surveys 2012, page 118).

This amount is often insufficient to recover and maintain soils above recommended targets of pH 5.5 and 4.8 in topsoil and subsoil, respectively.

A 2015 phone survey of 20 growers, conducted by this project, found the majority of growers are now using 2t/ha in order to speed the repair of soils.

As a result of Caring for Country project SP11-01226, growers in Western Australia are increasingly testing pH of soils below 10cm.

Growers understand the importance of lime in restoring soil pH, as seen by the increase in sales of lime in the northern wheatbelt (Liebe group technical audit results 2012).

However, according to Gazey and Andrew, lime sales of 1.1 million tonnes in 2012 (Effective management of soil acidity requires knowledge at the farm, state and national scale) are still less than half that of the 2.5 million tonnes required per year, indicating low adoption of the recommended practice.

Preliminary work by Davies, 2012 (Developing and assessing agronomic strategies for water repellent soils, page 71) has shown the applicability of a number of innovative techniques, including mouldboard ploughing and rotary spading, for incorporation of lime to depth.

Lime on the topsoil can be incorporated to a depth of 30cm enabling management of pH at this depth.

This work was to establish best practice methods and promote the effectiveness of these incorporation techniques throughout the rainfall zones of the northern agricultural region.

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