Implications of climate change for tillage practice in Australia

doi:10.1016/j.still.2007.09.018

Soil and Tillage Research

Volume 97, Issue 2, December 2007, Pages 318-330

https://doi.org/10.1016/j.still.2007.09.018 Get rights and content

Abstract

The world is experiencing climate change that in no way can be considered normal, and the challenge that this brings to agriculture is twofold. The first challenge relates to the continuing need to reduce greenhouse gas emissions that generate the changes to climate. Australia's National Greenhouse Gas Inventory estimates that agriculture produces about one-quarter of Australia's total greenhouse gas emissions (including land clearing). The main gases emitted are carbon dioxide, methane, and nitrous oxide. These gases are derived from high-value components within the agricultural production base, so reducing emissions of greenhouse gases from agriculture has the potential to provide production and financial benefits, as well as greenhouse gas reduction. Methane essentially derives from enteric fermentation in ruminants. Nitrous oxide and carbon dioxide, on the other hand, are strongly influenced, and perhaps even determined by a range of variable soil-based parameters, of which the main ones are moisture, aerobiosis, temperature, amount and form of carbon, organic and inorganic nitrogen, pH, and cation exchange capacity. Tillage has the potential to influence most of these parameters, and hence may be one of the most effective mechanisms to influence rates of emissions of greenhouse gases from Australian agriculture. There have been substantial changes in tillage practice in Australia over the past few decades – with moves away from aggressive tillage techniques to a fewer number of passes using conservative practices. The implications of these changes in tillage for reducing emissions of greenhouse gases from Australian agriculture are discussed.

The second challenge of climate change for Australian agriculture relates to the impacts of climate change on production, and the capacity of agriculture to adapt where it is most vulnerable. Already agriculture is exposed to climate change, and this exposure will be accentuated over the coming decades. The most recent projections for Australia provided by the CSIRO through the Australian Climate Change Science Programme, indicate that southern Australia can expect a trend to drying due to increased temperatures, reduced rainfalls, and increased evaporative potentials. Extremes in weather events are likely also to become more common. We anticipate that climate change will become an additional driver for continued change in tillage practice across Australia, as land managers respond to the impacts of climate change on their production base, and governments undertake a range of activities to address both emissions reduction and the impacts of climate change in agriculture and land management.

Introduction

The earth's surface has warmed over the last 100 years – roughly by 0.7 °C, and this is due mainly to increases in concentrations of ‘greenhouse gases’ in the atmosphere – carbon dioxide, methane, and nitrous oxide. These gases have increased by 30%, 150%, and 20%, respectively over this timeframe (Pittock, 2003). As with all other industries and sectors, agricultural activity has played a part in contributing to these increases.

Carbon dioxide results from the degradation of plant biomass, fossil fuel use, and changes in soil organic matter; methane is a by-product of enteric fermentation in ruminants; and nitrous oxide derives from nitrogen cycling in soils. All of these gases are derived from high-value components in the agricultural production base, and so reducing the emissions of greenhouse gases provides the opportunity for production, financial, and environmental benefits at the same time. However, understanding the processes involved in the regulation of these emissions, and their modelling and measurement remain a challenge.

The build-up of greenhouse gases in the atmosphere has a flow-on effect to all aspects of climate, and hence may have a direct impact on the capacity of agriculture to continue to generate the desired incomes for some regional communities. The impact of climate change on agriculture, and the capacity of agriculture and regional communities to adapt to climate change, comprise a second major challenge.

Tillage is one of the management variables that may enhance or retard emissions of greenhouse gases from agriculture, and may help maintain or improve the productive base under the conditions of climate change. This paper draws on tillage trends within Australia to investigate the extent to which tillage may be a tool to assist with the management of greenhouse gas emissions from agriculture, and secondly, it explores the extent to which aspects of climate change may provide additional drivers for continued change in tillage practice.

Section snippets

Trends in tillage practice in Australia

Tillage and land management practices clearly influence a whole host of interactions between soil structure and biota, and this in turn influences the stability of carbon and nitrogen within the soil matrix. Throughout this paper we define the different tillage practices as follows: cultivation – multiple tillage using a wide range of disc and tined scarifiers and cultivators; minimum tillage – one or two tillage passes before sowing giving full surface disturbance; and no-till – one pass at

Emissions of greenhouse gases from Australian agriculture

Agriculture is estimated to produce about 25% of Australia's national emissions when land clearing is taken into account (Fig. 4). This is an abnormally high proportion among developed countries (e.g. US ∼ 5.5% and EU ∼ 10%), reflecting the economy-wide balance between agriculture and energy-intensive industries within Australia. Globally, the figure is about 17% (World Resources Institute, 2007).

The agriculture sector appears to be Australia's largest source of methane and nitrous oxide emissions.

Trends in Australia's climate

Australia has experienced a general warming by about 0.7 °C from 1910 to 2000, and the trend is projected to continue. Using emissions scenarios of the Intergovernmental Panel on Climate Change (IPCC, 2001) and various global climate models, the CSIRO has projected further increases in average annual temperatures (relative to 1990) of 0.4–2.0 °C by 2030 and 1–6 °C by 2070. It is likely that there will be slightly less warming in some coastal areas and Tasmania, and slightly more warming in

Acknowledgements

The authors wish to recognise the strong contribution of Jo Mummery and Ian Carruthers of the Australian Greenhouse Office to the development of the AGO's Greenhouse and Agriculture programme, aspects of which are outlined in this paper. We also wish to thank Gary Richards, Sonia Bluhm, and Anthony Swirepik for helpful discussions.

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Implications of climate change for tillage practice in Australia

Abstract

Introduction

Section snippets

Trends in tillage practice in Australia

Emissions of greenhouse gases from Australian agriculture

Trends in Australia's climate

Acknowledgements

Soil Biol. Biochem.

Soil Biol. Biochem.

Soil Tillage Res.

Agric. Ecosyst. Environ.

National Greenhouse Gas Inventory

Soil organic carbon/soil organic matter

Basic Principles of Soil Fertility. II. Soil properties

BCG Crop and Pasture Production Manual 2005–2006

BCG Crop and Pasture Production Manual 2006–2007

Nitrogen oxides and tropical agriculture

Nature

Conservation tillage

Physiology and biochemistry of denitrification

Changes in microbial biomass and structural stability at the surface of a duplex soil under direct drilling and stubble retention in north-eastern Victoria

Aust. J. Soil Res.

The effects of direct-drilling and stubble retention on hydraulic properties at the surface of duplex soils in north-eastern Victoria

Aust. J. Soil Res.

Surface physical properties of a sandy loam soil under different tillage practices

Aust. J. Soil Res.

Climate Change Projections for Australia

Long-term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. I. Overall changes in soil properties and trends in winter cereal yields

Aust. J. Soil Res.

Soil microbial and biochemical changes associated with reduced tillage

Soil Sci. Soc. Am. J.

Predicted impact of management changes on soil carbon stocks for each agricultural region of the conterminous United States

J. Soil Water Conserv.