This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Subterranean clover's ability to bury its seed supports pasture persistence but makes commercial seed harvesting difficult. The industry relies on aging Horwood-Bagshaw (HB) suction harvesters, which collect seed from fully dry crops after repeated tillage and raking.
Two experimental studies investigated a very different approach: cutting and lifting plants with modified peanut-harvesting equipment while they are still green, then drying them in windrows for later collection and threshing. The research demonstrates that viable seed can be recovered well before complete crop desiccation, creating a potential pathway toward harvesting with fewer machinery passes and less soil disturbance. A commercial-scale trial at Capel, Western Australia, compared swathing a subterranean clover seed crop on Nov. 25 and Dec. 1, 2022, with conventional HB harvesting in February 2023.
A modified peanut digger cut the roots below ground, lifted the plants and placed them in windrows with the burrs attached, representing the first stage of a proposed two-stage system. Seed was collected from the windrows by hand because the second stage, mechanical pickup and threshing, was not tested. The equipment successfully lifted and windrowed the crop, although soil attached to the plants and weeds became tangled in the machinery.
These issues indicate that substantial equipment refinement and changes to paddock and harvest management would be needed. The most important finding was that subterranean clover could be harvested while plants still retained green material. Potential seed yield did not differ among the two swathing dates and the much later HB harvest, indicating that maximum seed yield had largely been reached before the crop was completely dry.
Swathing on Nov. 25 moved almost 100% of the available seed into the windrow. This fell to 84.2% on Dec. 1 as the crop became more senescent but remained higher than the 61.3% recovered by a single HB pass following three preparatory tillage operations. The earliest harvested seed was lighter and had lower and more variable germination.
However, seed swathed on Dec. 1 achieved 98.0% germination, comparable with 97.5% for seed harvested by the HB in February. Seedlings that emerged from the earlier-harvested seed generally showed similar vigor to those produced by later-harvested seed. These results suggest there is a harvest window in which plants remain intact enough to retain their burrs while the seed has developed sufficiently to maintain yield and quality.
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