Summary

This project investigated innovative methods for growers to harvest and sow pods from medic pastures to increase the cost-effectiveness of establishing medic pastures. Desiccation allowed medic pods to be harvested with a grain harvester. With storage of pods for two summers, Scimitar burr medic was the only cultivar where a low sowing rate achieved target plant density after sowing in February or March.

Background

Annual medics fix nitrogen, provide a break from cereal diseases, and increase the yield of subsequent grain crops. An inexpensive method of harvesting and sowing medic pods would increase the cost-effectiveness and renovation rate of run-down medic pastures, increase nitrogen input, reduce costs for subsequent grain crops, and increase overall farm profitability.

Research Aims

The core objectives of the project were to:

• Use novel methods to harvest medic pods on farm.
• Conduct a seed softening study to develop recommendations for sowing harvested pods.

In The Field

Harvesting trials were conducted with strand medic cv Seraph and barrel medic cv Sultan-SU at Palmer (low rainfall site) and Kingsford (medium rainfall site) in 2022 and 2023. At Palmer in 2022 a strip of each medic cultivar was sown at 50kg per hectare to mimic a regenerating medic pasture and was mowed until early flowering to simulate grazing. Medics were desiccated when many pods had turned grey, some pods had fallen, and plants were senescing. Four days later, pods were harvested with a grain harvester.

Seed softening trials were run in 2024 with pods of Seraph and Sultan-SU harvested with a grain harvester and stored for one to three summers, and naturally senesced pods of current cultivars (Cavalier, Penfield, Emperor, Sultan-SU, Jester-SU and Seraph) stored for two summers. Pods were placed inside envelopes of insect screen and placed on the soil surface in mid-February and mid-March. The pods were collected on April 20 and planted in pots in a shade house. Plant establishment was counted and used to calculate a sowing rate to achieve 200 soft seeds per square metre.

Broadcasting trials were conducted in 2023 to examine the impact of medic pods that had been stored for one or two summers. At Palmer and Kingsford, pods stored for one summer were broadcast at 80 or 120kg/ha and at 40 or 80kg/ha for pods stored for two summers.

Results

In 2022 at Palmer, 620kg pods/ha for Seraph and 350kg pods/ha for Sultan-SU were harvested from sown pastures and 700kg pods/ha for Seraph and 220kg pods/ha Sultan-SU medic in the simulated regenerating strips. In 2023 plant growth was insufficient at the Palmer site to attempt pod harvest due to the dry late winter and early spring.

At Kingsford in 2022 (wet spring year) a pod yield of 1,000kg/ha was achieved with Sultan-SU and 2,500kg/ha for Seraph. In 2023 (dry spring year) pod yield of 1,100kg/ha for Seraph and 800kg/ha was achieved for Sultan-SU. The harvester collected between 40 and 60 per cent of the total medic pods.

Broadcasting of pods failed to establish medic pasture. This was attributed to very low levels of seed softening and dry periods between rain events at the season break. It was concluded that sowing will achieve higher establishment as it allows pods to wet up.

Scimitar burr medic pods stored for two years could be sown at 30kg/ha in mid-March or mid-February. However, pods of Seraph, Sultan-SU and other current cultivars would need to be stored for more than three years which would not be viable for many growers.