Acidity threatens large areas of south-eastern Australia. AWI funded research to determine the cost effectiveness of applying lime to acid soils for wool production.

Also, increasing our understanding of soil biology under pastures has the potential to deliver increased pasture productivity in the future.

Growing productive pastures requires a foundation of healthy soil to support and sustain it. Having healthy soils involves managing your soils according to their capability, making the right fertilizer decisions, implementing solutions for problem pastures, maintaining ground cover, and looking after the soil microbes.

Soil salinity and acidity have a significant impact on pasture productivity. It is estimated that 2.4 million ha of land in Australia is affected by salinity and this costs Australia $270 million a year in lost agricultural production, infrastructure damage and environmental degradation.

There are also more than 7 million hectares of acid soils in Australia which costs approximately $300 million per annum in lost income. AWI funded research and development into soil salinity and acidity to provide woolgrowers with economic and environmentally sustainable strategies to manage and utilise these difficult soils.

The soil biota under pastures accounts for up to 75% of all living material in the system. It plays an important role in many of the ecosystem processes that are vital for plant growth. However, our current knowledge of and identification techniques for pasture soil biota is poor. AWI’s investment into soil biology increased our knowledge of pasture soil biology and developed better research techniques and tools for identifying soil biota and understanding its contribution to healthy soils.

Saline soils

Sustainable Grazing on Saline Land (SGSL), a Land Water & Wool sub program has developed techniques for reclaiming salt affected and waterlogged areas of the farm using a range of solutions of which tolerant pasture species that also provide valuable grazing for sheep is one option.

Most modern agricultural systems are based on annual crops and pastures that use less of the annual rainfall than the original vegetation. The excess rainfall drains below the root zone and joins the water table, causing it to rise and bring dissolved salts into the root zone. This results in dryland salinity and deteriorating soil health. There are currently 5.5 m ha of land classified as “at risk” of salinity and this is predicted to rise in the future.

Most dryland salinity is in southern Australia where the majority of land clearing has occurred.

Prevention by retaining native vegetation, is no longer an option in most of southern Australia. There are a range of possible approaches to managing dryland salinity and increasingly a mixture of these approaches are being applied. Options include:

• Reducing groundwater recharge by increasing the proportion of perennials (grasses and trees) in the landscape. AWI investments in EverGraze and Evergreen are focussed on increasing the proportion of perennials in the landscape.
• Adapting to salinity and developing productive pasture solutions for salt affected land
• Drainage to provide an outfall for rising saline water and to lower the water tables to below the root zone.

Salt tolerant pasture species offer the potential to make use of the excess water and increase dry matter production and livestock productivity.

SGSL has demonstrated that there are major opportunities to increase farm profitability and livestock production through changed management of saline areas. This approach also delivers environmental benefits through improved soil heath, biodiversity and removing salt from the surface of the landscape.

Acid soils

AWI funded projects that focused on economic returns from applying lime to pastures.

Soil acidity and the associated high levels of aluminium and manganese can significantly reduce pasture productivity.

AWI invested in two projects with NSW DPI looking into the effect of lime application on soil acidity, pasture productivity and wool production.

The MASTER (Managing Acid Soils Through Efficient Rotations) project ran for over 10 years, investigating the effect of applying incorporated lime on surface and subsoil acidity, pasture and  sheep productivity and economics. See more information on the MASTER project.

For many non-arable areas the incorporation of lime is not feasible. Very little information exists on the effectiveness of surface applied lime in reducing both surface and subsoil acidity or the economic impact of the application.

A second project near Canberra looked at the effect of surface applied lime and phosphorus on acidity, pasture and sheep productivity. The project assessed the potential for targeted use of phosphorus fertilizer and stocking rates to increase the returns from unincorporated lime application.

Soil biology

The Pasture Soil Biology program undertaken by AWI increased our understanding of soil biology under pastures and their potential impact on pasture productivity.

Australian Wool Innovation, Meat & Livestock Australia and the Grains Research and Development Corporation co-invested in fundamental research through the Pasture Soil Biology Program. The 3 priority projects in the program were: 

1. Root rhizosphere interactions with soil-borne organisms in pasture plants
   This project investigated the interactions between the root rhizosphere and soil borne organisms.
2. Molecular tools to study soil biological constraints to pasture productivity
   This project developed molecular assays for the identification of pathogens, general soil biota as well as key pasture species. These assays were field calibrated before being used as research tools as part of MLA and AWI projects on increasing pasture productivity.
3. Characterisation of pasture soil biology constraints
   This project characterised and quantified soil biological constraints in pasture systems.