Legume seed variants for germination timing

Western Australian research has supported this approach to winter legume pasture establishment for some years. NSW DPI research agronomist Belinda Hackney has explored summer sowing of unprocessed seed of several legumes for several years and regularly recorded far earlier establishment and far greater production using the technique.

The logic of the technology is that summer sowing of unprocessed seed of hard seeded varieties, allows them to convert to a "germination ready" stage via normal fluctuating temperatures (heat of the day to cool of the night). In contrast processed seed is altered to "ready to germinate" at time of sowing and would germinate prematurely if sown early. Germinating too early leads to seedling death as conditions are too hot for winter legumes.

Dr Hackney's research has shown that early sowing of unprocessed seed commonly results in them germinating on the first autumn rains and establishing quickly. In contrast processed seed is mainly sown after the autumn break. The delay, especially in drier years like 2017, 2018 and 2019, can sometimes mean establishment is months later and overall production far less.

So what is the hold up in adoption of this technology in NSW and other eastern states? Probably lack of marketable seed of these species/varieties in an unprocessed seed state. Also lack of an appropriate way to successfully incorporate rhizobia bacteria (responsible for legumes ability to build soil nitrogen) that will survive until seed germinates in autumn following a common dry hot late summer/early autumn.

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But good news. A few growers are now harvesting and retaining seed for sale in an unprocessed state. Anthony and Dick Ord, Marombi, Coolah and George Matthew and Richard Avendano, Boggabri have harvested yellow serradella and have retained some of it as unprocessed, but clean and good quality. It includes early and mid-maturing hard seeded varieties (King, Elgara, Avila).

Belinda Hackney reports Craig Rodham, Wagga Wagga, has harvested a good quantity of the new early maturing hard seeded pink serradella variety Frano. Much of this is likely also to be retained in an unprocessed state. Dr Hackney reports Frano suits medium to lower rainfall environments. Its seedling vigour is an outstanding feature commonly allowing it to get away earlier than other varieties and species.

In WA many farmers now harvest their own seed of species like serradella (yellow and pink varieties) and biserrula in seasons with a good spring. Not needing to process seed for ones own sowing if early sowing especially suits this strategy.

An equally important part of the early sowing strategy, especially when sowing into paddocks that have not previously grown a species like serradella or biserrula, is that rhizobia inoculum can be added at sowing via Alosca pellets. Research has shown rhizobia can survive in these unique clay based pellets for months, even in hot summer conditions. No other rhizobia application technique has this survival ability.

The only drawback to Alosca pellets is that the closest distribution centre is in South Australia. It is important to order, either direct or via connected agribusiness or independent agronomist, early to ensure supply can be organised in time for late January or February application. Cost per hectare is higher than normal rhizobia addition, but success is high and a successful establishment lasts indefinitely.

Research by Dr Hackney and others, including my own long term involvement, has shown introduction of species like serradella and biserrula can add dramatically to pasture productivity. Serradella can remain green and grow weeks longer into spring. It is bloat free, high quality, can perform at lower soil phosphorus levels, thrives in acid soils (as well as less acid ones) and has proven long lasting.

Next week: Big crops equals big nutrient loss.