Hardseededness
Hardseeds of Sothis generally soften in late autumn. This provides considerable protection against seedling losses from false breaks, unlike the seeds of subterranean and balansa clovers, which generally soften in early summer. The levels of hard seed of Sothis remaining in the soil after the first autumn are about 65%, making it suited to self-regenerating ley systems or short-term phase farming systems (where it needs to be resown at the beginning of each pasture phase).
Using Agwest® Sothis as a tool for weed management
In regenerating pastures, the delayed germination of Sothis is a useful tool in controlling herbicide-resistant weeds. The long period of delayed germination allows the use of non-selective herbicides (and grazing where possible) at the break of the season for a period of up to six weeks.
Trials have found this technique can control more than 90% of the weeds present without compromising potential legume production. The table below shows the impact on clover and weed densities when this management system was used in a trial at Bakers Hill. The density of Sothis was only reduced by 35% following the herbicide treatment, compared to almost complete loss of subterranean clover, while weed densities, particularly the broadleaf (herb) component, were substantially reduced.
| Sown legumes | Grasses | Herbs | |
|---|---|---|---|
| Sothis - unsprayed | 722 | 6325 | 3548 |
| Sothis - sprayed | 475 | 165 | 0 |
| Dalkeith - unsprayed | 5160 | 5295 | 3682 |
| Dalkeith - sprayed | 161 | 145 | 4 |
Sowing
As with other pasture legumes, Sothis should be treated as a crop in its first season to ensure maximum seed set. Minimise competition from weeds by spray-topping the paddock in the previous spring or select a paddock that was cropped to cereals or canola in which broad-leaf weeds were successfully controlled. In very weedy situations the sowing can be delayed for 2-3 weeks for better knockdown weed control with little impact on subsequent growth. Sothis requires rhizobial inoculation with Group C (clovers).
It should be sown at 10-15kg/ha when planted alone, but lower rates can be used when sown in a pasture mixture. Sowing depth of Sothis should be no more than 2cm. When establishing Sothis, ensure adequate nutrition, particularly phosphate and potassium. Monitor for insect pests and apply an appropriate insecticide if necessary. Graze lightly in the first season, particularly in spring, to allow maximum seed set.
