Mallee seep management strategies surface from on-farm trials

New collaborative research targets 'Mallee seeps' in South Australia and Victoria

Grower Stories
Kevin, Kate, left, and Louise Bond have twin-sown millet and sorghum to help remediate Mallee seep-affected areas on their family's South Australian property. PHOTO Clarisa Collis

Kevin, Kate, left, and Louise Bond have twin-sown millet and sorghum to help remediate Mallee seep-affected areas on their family's South Australian property. PHOTO Clarisa Collis

Aa

Lucerne and summer grains - sorghum and millet - help growers tackle seeps degradation

Aa

A new collaborative research effort is helping the Bond family tackle the swathes of sodden and scalded soil - so-called 'seeps' - that have increasingly surfaced across their cropping country in South Australia's Murray Mallee region.

There, about 12 kilometres east of Mannum, the Bond brothers - Kevin and Geoff - and their co-workers Daryl Sparks and Brett Newman, have seen 12 seep-affected areas emerge on the family's 2960-hectare property in the past 20 years.

To date, the Bonds estimate the complex, permanent pattern of land degradation has claimed about 25ha of their farmland, in the vicinity of sandy hills and ridges, since they made the transition from mixed farming to continuous cropping in 1999.

This seep-affected farm area is relatively small, but its impact on logistics for paddock operations, such as seeding, spraying and harvesting, is significant.

SEEP DYNAMICS

Studying the seeps on the Bonds' property for the past four years as part of research funded by Natural Resources SA Murray-Darling Basin, Chris McDonough, from Insight Extension for Agriculture, has identified a link between continuous cropping and seep formation.

Mr McDonough says better chemical control of summer weeds as part of modern intensive cropping systems is one of three main factors contributing to seep development. The other two factors are rainfall and landscape (deep sands over impermeable clays).

Specifically, more effective chemical control means there are fewer summer weeds, particularly skeleton weed, on the Bonds' paddocks to intercept and absorb rainfall on the deep sands which form sand hills and ridges.

As a consequence, rainfall moves quickly down through the water-repellent sand until it hits an impermeable layer of clay in the soil's subsurface layers.

The result is a 'perched water table' that moves laterally through the soil, causing seeps to surface lower in the farming landscape in mid-slope areas and at the bottom of swales.

In these seep areas, the topsoil becomes waterlogged, leading to bare patches of surface soil and, eventually, saline scalds prone to wind erosion.

MANAGEMENT STRATEGIES

Assisting the Bonds to manage their seeps is a range of management strategies trialled on their property by Mr McDonough.

Highlighting two of these strategies, the Bonds have been twin-sowing summer grain crops - sorghum and millet - on seep-affected areas to help soak up excess water, provide protective ground cover and prevent surface salt accumulation.

They have also been sowing lucerne in strips above seep areas to help reduce soil water recharge.

More information: Kevin Bond, 0435 081 240, krlabond@internode.on.net

Aa