Key Point

• ROSA can be used to identify soil amelioration options that are likely to provide the biggest economic returns when faced with many alternatives

What should be done and where should it be done first?

This is the key decision growers and advisers need to make when deciding on the potential financial return of alternative soil amelioration strategies at either a paddock or farm scale.

To help, Ranking Options for Soil Amelioration (ROSA), a user-friendly spreadsheet tool, has been developed to support decision-making for growers in Western Australia.

By estimating the financial benefit of each amelioration strategy relative to the potential yield gap posed by the soil constraint, ROSA provides an easy way to rank and interpret options.

Department of Primary Industries and Regional Development (DPIRD) staff, together with a consultant, developed ROSA to harness the wealth of information generated by a large GRDC investment - 'Soil Constraints West' - on a range of soil constraints including compaction, water repellence, topsoil and subsoil acidity and sodicity.

Industry benefit

ROSA was developed in consultation and collaboration with growers, researchers and advisers. Several versions were tested with potential users before its full release in January 2019.

By generating an expected financial return for various amelioration strategies on up to three farm soil production zones over 10 years, ROSA helps evaluate the economic benefit of different amelioration strategies - spading, ripping, gypsum, liming, claying, ploughing, wetting agents and combinations of these.

ROSA provides a logical framework to support economic best-bet amelioration decisions. - DPIRD researcher Jeremy Lemon

Results are presented as a range of standard economic analyses - benefit-cost ratio (BCR), return on investment (ROI), net present value (NPV) - together with cumulative cashflow over 10 years.

The tool is sensitive to the scale of the area to be ameliorated; small investments with small returns covering large areas often provide greater return overall than major investments over small areas.

An example is the use of soil wetters over a large area compared with claying a limited number of hectares due to the cost and work involved.

Simple to use

Once on the interface and outputs page, the user refers to the inbuilt map to select a WA soil zone, the budget limit for soil amelioration and the amelioration options they wish to consider.

For up to three farm production zones (FPZs), users nominate the hectares, one of eight major WA soil types for each and the level of each constraint or pH for soil layers. For each FPZ the user enters current average yields for four main crop types and the expected rotation for 10 years.

Users can change the default crop prices and cost of amelioration options - liming, ripping (with or without inclusion plates), soil mixing, wetting agent, claying or gypsum - to best reflect their own costs.

The user then clicks the 'Run ROSA' button and calculations are presented as a table showing the top five selected amelioration options ranked by BCR over a 10-year period (an example is shown in Table 1).

Additional information tabled for the best options is lime rate when selected, annualised cost per hectare, annualised profit per hectare, total cost and profit, ROI and BCR for the top five ranked treatments.

There is also a graphical presentation of the cumulative cashflow per hectare for these ranked options over a 10-year period (Figure 1).

Figure 1: Cumulative cashflow per hectare for ranked options from Table 1 over a 10-year period. Source: DPIRD

A copy of the ROSA tool as an Excel file can be requested from DPIRD. Additional support can also be sourced from DPIRD to help with use of the tool.

By August 2019, 142 people had requested a copy of ROSA: 39 consultants, 44 growers, 18 DPIRD researchers, 21 researchers outside DPIRD, nine grower group staff and 14 unknown.

This approach to developing a decision support tool has generated interest not only in further enhancing it for WA but also developing additional regionally specific versions for other parts of Australia.

DPIRD is currently developing a licensing agreement to use with other research groups interested in developing ROSA for other GRDC regions.

More information: Jeremy Lemon, jeremy.lemon@dpird.wa.gov.au, 08 9892 8413.