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RESEARCH ARTICLE (Open Access)
Contents Vol 76(6)

Swathing subterranean clover (Trifolium subterraneum) does not suck: a promising alternative to vacuum seed harvesting

R. C. Wiese https://orcid.org/0009-0006-7753-4256 A B * , M. H. Ryan A B , P. G. H. Nichols https://orcid.org/0000-0001-6778-5525 A C , W. M. Moss A B D , B. Wintle A , Y. A. Zago A , L. Hunt https://orcid.org/0009-0004-1479-9594 A , A. Hamblin A C and A. L. Guzzomi B C D
+ Author Affiliations
- Author Affiliations

A UWA School of Agriculture and Environment, The University of Western Australia, Crawley, WA 6009, Australia.

B Centre for Engineering Innovation: Agriculture & Ecological Restoration, The University of Western Australia, Shenton Park, WA 6008, Australia.

C Institute of Agriculture, The University of Western Australia, Crawley, WA 6009, Australia.

D School of Engineering, The University of Western Australia, Crawley, WA 6009, Australia.

* Correspondence to: ruby.wiese@research.uwa.edu.au

Handling Editor: Brendan Cullen

Crop & Pasture Science 76, CP24357 https://doi.org/10.1071/CP24357
Submitted: 30 November 2024  Accepted: 12 May 2025  Published: 30 May 2025

© 2025 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Context

Buried seeds of subterranean clover (Trifolium subterraneum) are typically harvested using the suction-based Horwood-Bagshaw Clover Harvester (HB) in late summer after preparatory tillage. This method relies on outdated equipment and causes significant soil disturbance. Swathing offers a promising alternative, whereby roots are cut and the sward windrowed before senescence for subsequent pickup and threshing once dried.

Aims

This study compared seed extraction efficiency and quality between swathing using a modified peanut digger as a first harvesting step and conventional HB harvesting.

Methods

Trials on a commercial subterranean clover seed crop in Capel, Western Australia, compared swathing using a modified peanut digger on 25 November and 1 December 2022 followed by hand collection of seeds to a single HB pass following standard tillage (14 February 2023). Measurements included canopy greenness, shoot biomass, soil moisture, seed extraction efficiency, seed weight, germination and seedling vigour.

Key results

Potential seed yield did not differ among treatments. As a first harvesting step, swathing achieved 100% (25 November) and 84.2% (1 December) seed extraction, compared to 61.3% for harvesting with the HB. November-swathed seeds had 82.6% germination, while December swathed (98.0%) and HB harvested (97.5%) had comparable germination. Seedling emergence followed the same trend. Swathed seeds weighed 17.1% (25 November) and 12.0% (1 December) less than HB-harvested seeds; however, seedling dry weights were mostly equivalent.

Conclusions

Although early swathing slightly reduced seed quality, swathing as a first harvesting step outperformed HB harvesting in extracting viable seed.

Implications

Swathing subterranean clover is a viable alternative to HB harvesting, addressing efficiency and environmental concerns associated with the traditional method.

Keywords: geocarpic seeds, harvest efficiency, mechanical swath, novel harvesting technology, peanut digger, seed harvesting, seed loss, seed quality, sub clover, subterranean clover, windrowing.

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