Objective

The Tarwin demonstration site in South Gippsland, Victoria is hosted by Schreurs & Sons, approximately 150 kilometres south-east of Melbourne. It aims to maintain soil carbon in a clay loam greenfield site which is gradually being converted from pasture to a vegetable production system rotation, predominantly celery, spinach and leek.
The aim is to enhance soil structure, nitrogen, and phosphorus levels by using green cover crops, compost and minimum tillage practices.

Rationale

The cover crops will compete with weeds and forage for nitrogen and phosphorus. By sowing the cover crop between celery and spinach plantings and using minimum tillage practices, soil disturbance will be minimised.

The trial area, previously fallow ground used for pasture, presents specific soil challenges: a low pH of 3.8, a Colwell P of 15, and 8% soil organic carbon. Given the observed soil carbon losses in similar blocks on the same farm.

Trial Theme and Topic

Carbon and Climate – Resilient Production Systems (Adaptation)

This trial focuses on the themes of carbon and climate resilience, emphasising soil health through the use of cover crops, rotations, minimum tillage, and composting to improve soil structure. By adopting these practices, a more sustainable and productive farming system can be created.

Crops and Rotation

Due to weather conditions, there was a significant delay in spreading lime and seeding the cover crop. Going into spring, the initially planned winter (June) cover crop including Faba bean (Vicia faba) to add nitrogen and recover nutrients with Cereal rye (Secale cereale) as a control to suppress weeds had to be skipped.
Instead, the trial commenced with a spring cover crop blend of buckwheat (Fagopyrum esculentum) and vetch to forage for nitrogen and phosphorus and to suppress weeds. The cash crop of spinach was sown in summer (February), followed by celery sown using strip tillage in May, 2024. A fast-growing warm-season cover crop with a large biomass providing competition against volunteers, such as buckwheat and/or Japanese millet (Echinochloa esculenta), was sown in February/March.
Then a second crop of spinach followed by leek for the winter months.

Soil Type and Texture

The soil is loam-clay, friable with low pH and low phosphorus, but high soil organic carbon.

Climate and Microclimate Impacts

The area is exposed to wind, which blows the topsoil away, as well as heavy rainfall events.

Trial Start and End Date

The trial started in June 2023 and will continue for a minimum of 3 years, potentially up to 5 years as a core demonstration site.