In well drained, adequately fertilised soils all of the alternative legume species are suitable. In poorly drained and slightly saline soils, both balansa and persian clovers have some tolerance to these soil conditions and would therefore be suitable.
In contrast, serradella, arrowleaf and crimson clover are less tolerant of waterlogging. Arrowleaf clover has a deep rooting habit, which can access soil moisture at depths. It is suitable on soil profiles containing a perched watertable at 1.5 m.
Serradellas have some tolerance to poor soil nutrition, high soil acidity and high aluminium levels. Serradellas are suitable on acidic sandy soil types as well as in mixtures with subterranean clover.
Crimson clover also has some tolerance to acidic soils. In contrast, persian clover has a low tolerance to high soil acidity.
Importantly, as with subterranean clover and annual ryegrass the maturity of the individual alternative legume cultivars will need to be matched to the length of the growing season.
Inoculation and lime pelleting:
Inoculation of each of the different alternative legume species with the appropriate rhizobia is necessary if they have not been previously grown in the paddock. Because new improved rhizobia stains are now available it is suggested that in older alternative legume paddocks inoculation be undertaken as a relatively cheap insurance. Lime pelleting should not be used on serradella.
Sowing technique:
The small seeded species, e.g. balansa, persian and arrowleaf, should be sown at 2 - 5 kg/ha, whilst the larger seeded species, crimson clover and Cadiz serradella should be sown at 5-10 kg/ha. The soft seeded Cadiz pink serradella readily germinates from the pod segment in contrast to the hard seeded yellow serradellas.
Due to the relatively low price of Cadiz it can be sown at higher rates, e.g. 10 kg/ha, if a high seedling density is required. The more expensive dehulled and scarified yellow serradella seed, e.g. Avila can be sown at 2-3 kg/ha.
In addition, farmers can also sow a low rate of up to 5 kg/ ha of annual ryegrass with the alternative legume mixture. Annual ryegrass will compete against the alternative legume but it will provide some early feed for grazing and will lessen the danger of bloat.
In a few isolated cases cattle bloat has occurred in paddocks growing a heavy balansa sward. In contrast, serradellas have never been implicated with cattle bloat. Recently a 3 year establishment/persistence trial was completed at Vasse research station on a sandy soil site with a mixture of alternative legumes including serradella, cvs Cadiz and Avila, arrowleaf clover, cv Cefalu and biserrula, cv Casbah.
Over the three years the two serradella cultivars have successfully dominated the alternative legume component. Over time it is anticipated that the hardseeded Avila will increase relative to the soft seeded Cadiz as it is less vulnerable to summer rain.
This research has demonstrated that, in the establishment year, drill sowing rather than topdressing will result in more than a threefold increase in legume germination density, spring legume content and legume seed yields.
The ‘best practice’ management in year one was to set up a sustainable seed bank for long-term persistence.
This entailed:
- opportunistic grazing to promote the sown alternative legume sward;
- foregoing fodder conservation to promote maximum seed production, i.e. set up the seed bank; and
- grazing the residual dry matter over summer to both utilise this high quality feed resource and importantly promote seed softening and seedling emergence at germination.
In the first year regenerating swards the drill sowing treatments again had higher serradella seedling density, dry matter yields, spring serradella content and serradella seed pod yields in comparison to the topdressing sowing technique.
This is directly attributable to the higher seed bank set up in the establishment year by drill sowing and will greatly assist in the long-term persistence of the sward. However, the beneficial effect of drill sowing was not as evident in the second regeneration year. Here the seed yields and subsequent natural regeneration from the establishment by topdressing increased to a sustainable level at the end of the first regeneration year.
The topdressed sowing technique needed an additional year to build its seed pod bank up to a sustainable level of approximately 150 kg/ha. In general, with alternative legumes a high seed bank is essential to help compensate for both the small seedling size and their relative slow growth rates in the autumn/ winter feed gap period.
An inadequate legume seed bank can result in a low dry matter yield, which can be compounded by poor quality if the sparse legume germination density is displaced by weed competition.
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