Tarwin, Victoria

By Paulette Baumgartl, Applied Horticultural Research

With the help from tech company AgriKnow, Soil Wealth ICP has introduced an innovative online platform to connect vegetable growers with ongoing insights from the Tarwin site. This technology enables users to explore interactive features, such as virtual walk throughs and soil parameter comparisons, enhancing understanding of sustainable agricultural practices.

Users can take a 360-degree virtual tour of the site, comparing different treatments and their impact on soil and crop growth.

Interactive icons within the platform reveal 3D cross-sections of soil and root development, offering an immersive and educational experience. In addition to these interactive features, the platform provides comprehensive data on the trial site’s soil type, crop rotation, and climate effects. Summaries of the four treatments used, along with aerial and NDVI imagery, offer a detailed view of the ongoing trial.

The platform also houses various educational resources, including videos featuring grower Adam Schreurs. These videos delve into the trial’s purpose, the importance of soil carbon, and labile carbon test results. Updates on crop growth, nutrient levels, and other key metrics are also available, providing a complete picture of the trial’s progress and findings.

The trial

Set on clay loam soils, the greenfield site is transitioning from lush pasture to vibrant vegetable production. The focus of this trial has been on maintaining and enhancing soil carbon.

The rotation features high-value crops like celery, spinach, and leek, with a strong emphasis on sustainable soil management. Key practices include incorporating green cover crops, applying nutrient-rich compost, and embracing minimum tillage to improve soil structure and fertility. This dynamic site showcases approaches to achieving long-term soil health in vegetable production systems.

Soil carbon, which constitutes about 50 percent of organic matter, is vital for soil health, crop resilience, productivity, and greenhouse gas sequestration.

“Without soil carbon there the soil is dead to me. It’s just so important to grow. We’ve seen areas where our soil carbon is depleted and things struggle to grow,” host grower Adam Schreurs says.

High organic carbon levels enhance microbial activity, nutrient cycling, and soil stability while reducing erosion and buffering against soil acidity. This trial highlights the critical role soil carbon plays in sustainable vegetable production.

Baseline conditions and treatments

Baseline measurements in June 2023 revealed organic carbon levels ranging from 5.5-5.9 percent. The soil structure was stable in the control area but unstable in the trial area, likely due to prior deep ripping and cultivation. Phosphorus and nitrogen levels were relatively low, ranging from 28-34 kg/ha and 23-28 kg/ha, respectively.

Treatments (Table 1) included the use of cover crops such as buckwheat, vetch, and millet, sown and terminated sequentially between January and March 2024. Fertiliser inputs were applied to the control area prior to spinach being sown as the first cash crop.

Spinach was followed by celery and leek rotations. Minimum tillage with new strip-till equipment was employed to maintain cover crop residue.

Key results and insights

Results from the trial showed that Treatment 4, which used cover crops with minimum tillage, had the smallest reduction in soil carbon (-0.1 percent) compared to the control (-0.5 percent) (Figure 1). The minimum tillage treatments also demonstrated better bed stability and rooting depth, particularly after heavy rains.

Nitrogen levels increased significantly in the second year for treatments that received fertiliser inputs, with Treatment 4 returning more nitrogen to the soil than was applied, likely due to the decomposition of cover crop biomass.

The carbon-to-nitrogen ratio improved in treatments with cover crops, supporting microbial nitrogen breakdown. Soil health analysis revealed limited arbuscular mycorrhizal fungi (AMF) presence in both control and trial areas.

TABLE 1: Different treatments in the trial area

Soil-borne pathogens, including sclerotinia and rhizoctonia, were more prevalent in the trial area, while pest-suppressing microbes were detected in the control area. Nematode diversity and abundance provided further insights into soil health, with undisturbed reference areas showing higher biodiversity compared to cultivated blocks.

FIGURE 1: Changes in organic carbon percentage by treatment

The virtual walk through and full case study of the Tarwin demonstration site, including a comprehensive overview of the trial’s objectives, treatments, and findings is available at soilwealth.com.au

FOR MORE INFORMATION
Contact project leaders Dr Gordon Rogers on 02 8627 1040 or gordon@ahr.com.au and Carl Larsen on 03 9882 2670 or carll@rmcg.com.au