GROWERS and advisers will be better equipped to manage soil constraints in their paddocks after the development of a three-dimensional (3D) mapping strategy, currently trialled at farms in western Victoria.

So far, four farmer’s paddocks have been mapped using the new sensing techniques, located in the state’s medium-rainfall zone at Nurcoung, Nurrabiel and Wallup and in the high-rainfall zone at Wickliffe.

This will give a greater understanding of the dynamics and location of constraints to crop production that lurk in the depths of the soil profile.

Agriculture Victoria senior research scientist, Professor Roger Armstrong is leading the research, working closely with a team of scientists, technicians and PhD students.

The research effort is part of the Victorian Grains Innovation Partnership (VGIP) between Agriculture Victoria and the Grains Research and Development Corporation (GRDC).

“Growers often have trouble identifying what the soil constraints are in their cropping paddocks, the soil profile can be highly variable, and often they only analyse the topsoil,” Prof Armstrong said.

“However, our research is enabling us to use soil sensor technologies to 3D-map the location and severity of multiple soil constraints at a paddock scale.

“It’s quite unique in terms of its soil mapping approach.”

The soil maps are created using a variety of rapid soil sensing technologies including EM38 and gamma radiometrics.

Ground Penetrating Radar is also being trialled which can identify where and at what depth the B horizon (subsoil) occurs in duplex (sand over clay) soils.

In areas such as the Western Districts, this B horizon is a major throttle to drainage and is a major factor in the extensive water logging that commonly occurs.

“We then use the soil maps we have created and overlay them with ‘above-ground’ crop growth rates, which were developed using a range of ground based and satellite crop sensor technologies,” Prof Armstrong said.

“Combining the soil and crop-focussed maps links the 3D spatial arrangement of soil constraints within a paddock to crop performance.

Prof Armstrong said that this approach could be used to better target management strategies.

One strategy, for example, is subsoil amelioration (manuring) using organic matter, gypsum, lime or nutrients. This strategy can cost $1400 a hectare and economic analysis has shown that it can pay for itself in about three to four years depending on potential productivity, the nature of soil constraints and what depth these are located in the soil profile.

Many farmers said they were reluctant to invest such a high upfront cost however, so another option was to simply reduce the area treated by targeting the specific areas in a paddock where the soil constraints occur and are close enough to the soil surface to be able to be treated based on information from the 3D mapping.

The 3D methods, combined with data gathered from satellites and subject to climate variability, expand the information farmers have on their soil compared to traditional soil sampling methods.

“Our findings will inform the way growers and their advisers will be able to assess soil-based crop constraints in the future and how to tackle the problem to achieve optimal crop production and maximum profitability,” Prof Armstrong said.

Commercial crops grown in these paddocks included wheat, barley, faba beans and canola.

The VGIP aims to improve the enduring profitability of Victorian and Australian grain growers through world-class research and innovation.

For more information about research at Agriculture Victoria, visit agriculture.vic.gov.au/about/our-research.

For more information on the project led by Prof Armstrong, visit bit.ly/3xW2dUP.