Salisbury: Rehabilitating the Scalds

A regenerative agriculture case study from The Marra, north-central NSW.

Tour the farm with Will MacAlpine

Ready for drought, ready for rain

Salisbury is typical of Dorothea McKellar’s ‘land of droughts and flooding rains’. There are no permanent watercourses on Salisbury. Water supply is rain and bores that tap the Great Artesian Basin. Average annual rainfall is about 450 mm on the property or 405 mm as measured at the nearest meteorological station, perhaps indicating high local variability. The average and median monthly rainfall sometimes falls in a single day, sometimes causing regional flooding. Conversely, very little rain falls for substantial periods.

Will MacAlpine is clear that for the grazing business to cope, obtaining maximum benefit from rainfall events and minimum damage during dry periods, ‘we must be ready for drought, and we must be ready for rain’. The strategy to achieve that comprises a number of tactics:

• Increase the area of productive grazing land by rehabilitating scalded land.
• Cap the artesian bores to control water supply.
• Control kangaroo grazing pressure.
• Manage sheep grazing pressure in dry periods by moving sheep to holding pens and hand feeding them, and by deferring joining young ewes.

In practice, these tactics are interlinked or interdependent.

Rehabilitating the scalds

A scald on Salisbury, still remaining in 2020, showing the hard-packed surface soil and elevated root systems of dead plants, indicating the depth of topsoil lost to wind and water erosion.

Although rehabilitation work was begun on Salisbury in the 1970s by the previous owners, when the MacAlpines took over the property Grant MacAlpine could land his light plane almost anywhere on the property. After seeing promising results on properties nearby, the MacAlpine family continued rehabilitation in the 1980s and 1990s. Works ramped up in 2009 and 2012 when government grants were available.

The methods that have been used successfully for several years on Salisbury involve using a grader to build low ponding banks to hold rainwater to a depth of 10 cm or so. These are circular on flat ground and semi-circular (a ‘horseshoe’ shape) on scald with a mild slope. The opening of the horseshoe is to the up-slope side, so that run-off collects within the banks. Each pond covers about 0.4 hectares. The grader used to construct the banks is also used to disturb the soil surface within the ponds in strategic locations (Thompson 2008). Saltbush seed – some of it collected on the property – is sown over the disturbed surface. Running cattle over the ponded area after the surface had been softened by rain was used to disturb the soil surface in a previous Soils For Life case study of a property near Brewarrina.

The effect of the ponding banks and disturbance is to hold water from the intermittent heavy falls. This then infiltrates – albeit slowly – to leach salts from the surface and provide moisture down the soil profile. The banks and disturbance within them provide a barrier to wind-blown sediments and plant material, which collects and starts to form an organic-rich surface layer. The saltbush seed, together with whatever seed is delivered by wind, sheep and birds, then has somewhere to germinate and moisture to tap in the soil profile. The natural processes of ecological succession have effectively been given a ‘kick-start’ and can take their course. To date, about half of the scalded areas on Salisbury have been treated in this way.

The results can be seen here:

Capping the bores

Four artesian bores that were installed early in the 20th century and have been flowing ever since supplement Salisbury’s intermittent water supply from rainfall. The aggregate potential flow rate is 9 L/second (284 ML/year, or about 114 Olympic swimming pools). However, the volume required to support grazing stock is estimated at around 1 L/second, so the rest (around 250 ML/year) runs away to waste via bore drains. The wasted water supports a kangaroo population far in excess of what would be there naturally, whereas a tank and trough system can be managed to restrict water supply.

One of the four bore drains that together used to carry away around 250 Ml/year of surplus water.

Capping the bores maintained the pressure of the underground artesian aquifer and used only the amount of water needed for stock. A threat by governments to charge for water used in excess of stock requirements focused the MacAlpines’ action. A subsidy from the NSW Government [1] helped too. Following the mandated specifications, each tank supplies two nearby troughs – the second being presumably for backup in case one failed. So far, two of the four bores on Salisbury have been capped.

Tank and troughs that have replaced free-flowing artesian bores.

Managing grazing pressure

This is the biggest concern for the viability of the Salisbury business is a seemingly endless supply of kangaroos willing to move on to the property. Generally, they come from the north and arguably in far higher numbers than would have been possible before graziers started providing water sources.

Managing the kangaroo population requires a massive investment in specifically designed fencing. Fences like that will also exclude wild dogs that be-devil sheep graziers elsewhere and that the MacAlpines expect in the Marra region before long.

The cost of kangaroo-proof fencing is around $4,000/km for materials and the property boundary is about 50 km, so a substantial investment is required. Fortunately, the NSW Government has provided a low-interest loan for this.

Kangaroo-proof fence: extra height wire supported by fewer posts; mesh apron to prevent kangaroos pushing under the bottom wire; two electrified mid height wires powered by solar panels.

Sheep grazing pressure is managed in dry periods by moving sheep to holding pens and hand feeding them with grain and straw. This is especially useful for ensuring that ewes chosen for breeding have optimum nutrition.

Further tactics to reduce grazing pressure include:

• deferring joining young ewes so that their grazing requirements are minimised; and
• selling older ewes or passing them on to the farm run by Alex MacAlpine at Grenfell, NSW.

Will and Grant MacAlpine make these decisions from time to time [2], taking particular note of animal and pasture health.

Adapted to a variable climate

In summary, the grazing enterprise at Salisbury is well adapted to the highly variable, semi-arid climate. Amongst their many benefits, the water ponds bring more areas into production and generally improve the appearance of the property. Capping the bore, erecting wildlife-proof fencing and managing stock numbers controls the total grazing pressure and ensures sustainability so that the MacAlpines are ready for drought and ready for rain.

[1] Not as generous as the subsidy in Queensland.

[2] Especially over the summer period when a “feed gap” would develop if rain was inadequate.

THIS CASE STUDY WAS PUBLISHED IN SEPTEMBER 2012 AS PART OF THE SOILS FOR LIFE INNOVATIONS FOR REGENERATIVE LANDSCAPE MANAGEMENT PROJECT.
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