Soil indicators and their use by farmers in the Billabong catchment, southern New South Wales.(Report)

Introduction

Earth's ecosystems depend on functional soil. Soil is critical for decomposition and nutrient cycling, which in turn sustains plant and animal productivity, supports biodiversity, enhances air quality, and maintains water quality (Torsvik et al. 1990; Doran 2002; Sojka et al. 2003). Humans exert a major influence on the world's soil, in particular through agricultural land use. To meet the increasing demands of the growing human population, contemporary agricultural methods in developed countries have created an industrial system of high inputs and outputs. However, increased agricultural production has come at a high cost to soil resilience, and aspects of the industrial approach threaten the vital ecosystem services soil provides (Doran 2002).

This threat to ecosystem function is recognised in current public discourse on soil management, which is framed in terms of 'soil health', as exemplified by the 2006 State of the Environment report (Australian Government Department of Environment and Water Resources 2007). State and Federal governments currently fund various soil health projects, including the Australian Government's 'Healthy Soils for Sustainable Farms Programme' (Department of Agriculture, Fisheries and Forestry 2007). Because governments have limited powers to influence management on privately owned farms directly, these soil health projects follow traditional agricultural extension practice by providing a mix of information and incentives to encourage farmers to undertake recommended 'best practice'. What constitutes best practice in this context is predominantly determined by soil scientists. The perspectives of soil specialists are reasonably well documented, as it is they who publish most papers on soil and its management. However, how soils are understood by farmers, and how that understanding informs their farm management decisions, is less well documented. The research presented in this paper sought to better understand how dryland farmers in the Billabong catchment of southern New South Wales (NSW) use soil indicators to inform their management decisions.

Soil indicators

The use of soil indicators can be traced back to Roman philosophers who suggested sight, taste, touch, and smell as qualitative criteria for evaluating soil and its suitability to grow particular crops (Doran et al. 1996). Experiential, anecdotal soil indicators of this type supported traditional agriculture until relatively recent times, when a more explanatory, quantitative approach developed in parallel with industrial fanning. Previous research projects have identified the variety of soil health/soil quality indicators available for farmers in different situations, and their results are summarised in Table 1.

Much of the published research has sought to assess the 'value' or 'accuracy' of traditional soil indicators in comparison with modern scientific technology (Desbiez et al. 2004; Agbenin and Adeniyi 2005; Mowo et al. 2006). Many visual indicators are dismissed in the scientific literature as unreliable (Schwenke et al. 2003). There is also some literature available on the use of laboratory-based soil tests. Lobry de Bruyn and Abbey (2003) found that many farmers regard soil testing as a way of eliminating poor crop performance from causes they cannot see. However, some farmers regard soil testing as unreliable (Hayman and Alston 1999). This scepticism is possibly attributable to the farmer' s perception of soil testers, rather than the tests per se, as the people doing the testing are employed by agricultural companies to sell fertiliser and to give advice (Lobry de Bruyn and Abbey 2003). Wilkinson and Parminter (1997) suggested that soil tests were used mainly to help solve a particular problem, and complemented rather than replaced informal monitoring. Indeed, Australian farmers appear to use multiple soil indicators. For example, as well as using scientific testing for nutrition, organic carbon, and soil pH, some farmers in the central NSW area also used more traditional methods such as visual observation and the feel of 'the dirt between their hands' (Lobry de Bruyn and Abbey 2003).

Although it is clear that both technical and non technical soil indicators are accessed by farmers, there is little information about how the farmers use these different sources of information in their farm management decision making. In particular, there is no indication of why one soil indicator may influence decision making more than another. This is significant, as research has shown that changes to one indicator may create significant changes to several others, making the choice of indicator more complex (Andrews et al. 2002). Nor is there much published information about how farmers make sense of possibly conflicting information.