Getting it right 

Once a seed bank is established, an ongoing pasturecrop rotation can be established. The length of the cropping phase that can be implemented will depend on the hard-seed characteristics of the legume species and variety of legume within species.

MLA-funded research found that if good establishment methods were used, the small (generally much smaller than sub-clover or annual medics) and hard-seeded nature of these legumes (arrowleaf clover, biserrula, bladder clover and gland clover) enabled a large seed bank to be established for reliable regeneration.

Sowing time and pasture production
Timing of sowing is important – summer sowing allows plants to establish and utilise higher autumn temperatures, producing a greater leaf area and therefore high quantities of dry matter before cooler temperatures arrive.

Earlier sowing can also provide greater competition against weeds. Scarified seed can be dry sown ahead of the autumn break or after the autumn break if an additional weed knockdown is desired.

Later sowing generally decreases first-year herbage production as plants grow slowly if they emerge in the cold conditions of late autumn and winter. Later sowing can also significantly reduce seed production.

Figure 1: Herbage production (kg DM/ha) for biserrula, bladder clover, gland clover, French serradella and yellow serradella. SS = summer (February) sown in pod. LS = Sown (May) as scarified seed

Seed preparation and inoculation
Appropriately inoculated legumes will be more successful in forming an adequate number of nodules and reaching nitrogen fixation potential. The appropriate inoculant group must be used for each legume species. The inoculant contains the appropriate strain of rhizobia for specific legume species.

Arrowleaf clover, bladder and gland clover require Group C inoculant (the same as sub‑clover), biserrula requires Group BS inoculant and serradella requires Group S. If you are sowing a mixed pasture, for example one that contains gland clover and serradella, it is critical to use both Group C and Group S inoculant.

The form of inoculant is also a critical consideration. Peat and freeze-dried inoculants need moist soil for survival. Clay‑based granular inoculant is suitable for use in dry soil conditions and can be drilled into the soil.

Sowing depth
The new legume species are small seeded, generally much smaller than sub-clover, and therefore should be sown no deeper than 10mm.

Sowing rates
Summer sowing and twin sowing rates of in-pod seed (serradella) are 20–30kg/ha and for unscarified seed (arrowleaf, bladder clover, biserrula and gland clover) 12–15kg/ha. A long-life granular inoculant must be used at 10kg/ha to help establish good rhizobia in the root zone.

Scarified seed can be sown at 5–10kg/ha for a monoculture, or 4–6kg when being sown in a mix with grasses or lucerne.