Tips for autumn pasture sowing success

Success also is maximised if a few aspects are adhered to.

Sowing rate is a big part of the cost and includes a host of species, many of which may not suit a given environment. It is important to select species and varieties that suit a given rainfall area and soil type. I remember years ago, a NSW DPI Wagga Wagga research agronomist emphasised why to include multiple perennial grass species when Phalaris was the only temperate perennial in the given area that was capable of long-term persistence.

NSW DPI Tamworth research has shown that four to nine tropical grass plants per square metre of species like Premier digit grass are all that is required for maximum production. For lucerne, 20 plants per square metre are around what is needed for many environments. For temperate perennials like Phalaris, 20 plants per square metre are likely more than sufficient.

Sowing quality seed with good equipment that can accurately place small seeds, as most perennials have, can contribute to good establishment at relatively low perennial species sowing rates. Lucerne, for example, has around 450,000 seeds (clean seed basis) per kilogram. Sowing at 2 kilograms per hectare will therefore supply around 90 seeds sq/m. Good quality seed at this sowing rate, sown into good moisture at 10 to 15 centimetre soil depth, normally can guarantee more than 20 plants sq/m.

Two kg/ha for phalaris is equivalent to 130 seeds sq/m, for tall fescue 80 seeds sq/m, perennial ryegrass 110 seeds sq/m and cocksfoot 260 seeds sq/m. These are approximate and do not allow for coating, which can lower seed numbers by 30 per cent or so, depending on coating levels. Also, check seed germination levels for determining viable seeds/kg.

Basically, seed size and sowing rate analysis carefully assess what is commonly being advocated as excessive sowing rates with coexisting high costs. Depending on sowing conditions, a common sense compromise is to decide how many perennial plants are required per sq/m and decide what a sensible sowing rate to achieve this is needed.

Read more: How to balance soil nitrogen for top quality pasture

Establishing perennials successfully also depends on many other factors, such as excellent weed control, stored soil water, good soil fertility and guarding against pests like red-legged earth mites and blue oat mites.

Sowing of annuals into existing pastures, especially grass-based ones, including native pastures, also helps with seed size, species and sowing rate analysis. Unlike perennials, annual legumes can commonly be successfully established by drilling them into existing pastures and also by topdressing, although the risk of success is less than the former.

Annual legumes like sub clover, medics and serradella have larger seeds, generally more vigorous seedlings and can compete better with existing vegetation. However, success is also enhanced if seed is applied ahead of the autumn break so that they can compete on equal terms with existing soil seed populations (which can be a multitude of grass and broadleaf plant species).

Because annual legumes, if successfully established, can set hundreds of seeds per plant, sub-optimal populations can increase rapidly given careful management and reasonable seasonal conditions. While it is commonly advocated to sow these at relatively high rates to help encourage rapid development to ideal density, the same can be achieved at lower sowing rates, but perhaps an extra year or two is required to build to a good soil seed level (for future autumn germinations).

Sowing winter annuals ahead of the autumn break, either via drilling into the pasture or via topdressing, can present difficulties with the survival of rhizobia suited to the particular legume. If germinating rains don't follow soon after adding them to the pasture, rhizobia added via conventional seed coating, even lime coating, won't survive long. Alosca pellets are a relatively new technology than can help avoid this issue.

Next week: Pulses in most profitable crop rotations.