Priorities for improving soil condition across Australia’s agricultural landscapes

There is a renewed international focus on soil management because of increasing concerns about the implications of current trends in soil condition. In Australia, soil acidification, unsustainable rates of soil erosion, loss of soil organic carbon and nutrient imbalances (deficiencies and excesses) are recognized as significant threats to soil function. If left unchecked, these problems will constrain Australia’s ability to take advantage of agricultural opportunities created by a growing population and demand for exports. The threats have the potential to impose significant costs because ecosystem services provided by soils will be impaired.

This report provides an overview of trends in soil condition across Australia’s agricultural landscapes. It has been prepared to assist the Australian Government design the next phase of the National Landcare Program and in so doing, meet its international obligations relating to sustainable development, climate change, biodiversity and sustainable soil management.

Soil acidification: The extent and severity of soil acidification is much greater than previous assessments have indicated. The intensification of cropping, and in particular the increase in nitrogen fertiliser usage and product removal, combined with inadequate liming, are causing significant acidification across large areas that were previously considered to be unaffected.

Soil carbon: Arresting declines or increasing soil carbon stocks has the potential to maintain or enhance soil resilience, sustainability and productivity as well as provide opportunities to mitigate greenhouse gas emissions. This highlights that increasing soil carbon stocks will be challenging across many agricultural landscapes in Australia. Success will depend heavily on the way individual landowners implement soil management measures (e.g. through the timing of cropping and grazing operations). The regions with the greatest potential for increasing soil carbon stocks are in the south east of Australia.

Soil erosion by water1: The control of soil erosion by water has the potential to preserve the soil resource and have a major influence on other soil attributes including soil organic matter, nutrient status and rates of acidification. Soil erosion is tightly linked with downstream water quality both within the rural enterprise (e.g. stock watering points and farm dams) and off-site (e.g. in rivers, reservoirs, estuaries and the ocean). The erosion of surface soils is a long-standing problem in Australia. Although there are regional success stories, the rates of hillslope erosion across Australia’s rural landscapes are still much greater than the rates of soil formation so a net rundown of the soil resource is occurring. The report emphasizes that the intensification of land use in Northern Australia should avoid areas with erodible and dispersive soils if extensive gully erosion and the mistakes of the past are to be avoided.

Nutrient imbalances: Nutrient decline is an ongoing concern but Australian agriculture has a long history of responding to deficiencies as they emerge. Despite this history, chronic and possibly irreversible nutrient decline is occurring across large tracts of once naturally fertile soils, particularly in the northern cereal growing areas of eastern Australia. The situation for nutrient excess is more complex and less certain. A large and ongoing increase in the use of nitrogen fertiliser is occurring and this has implications both on-site (e.g. acidification, emergence of other nutrient deficiencies) and off-site (e.g. nitrate in groundwater, greenhouse gas emissions).

A better understanding of the consequences of this intensification is required. Achieving sustainable soil management is complex and commentary is provided on key factors for success. These include: (1) coordinated programs of soil research, development and extension; (2) experienced and highly motivated specialists; (3) up-to-date soil mapping and monitoring at resolutions relevant to farm management; and (4) technical solutions for erosion control, sequestering carbon and sustainable farming. Of critical importance is the need to integrate public sector and private sector data streams so that farmers, industries and governments are aware of the key threats to soil function.

Rankings are provided for addressing soil acidification, increasing soil carbon, controlling hillslope erosion by water and managing nutrient deficiencies and excesses. These rankings provide a framework for prioritizing investments across NRM regions. It is emphasized that prioritization is also required within regions. The project has produced several fine-resolution data sets that can be used for district planning within each NRM region.

 

Published: 12 Oct 2017

Author(s): McKenzie, Neil; Hairsine, Peter; Gregory, Linda; Austin, Jenet; Baldock, Jeff; Webb, Mike; Mewett, Jodie; Cresswell, Hamish; Welti, Nina; Thomas, Mark

ISBN: 9781486309405