Serradella survives and shines in tough season

Serradella survives and shines in tough season


On Farm
Serradella (yellow flowering) survived second driest late autumn winter early spring on record to recommence growing, flowering, and seed setting following October rains.

Serradella (yellow flowering) survived second driest late autumn winter early spring on record to recommence growing, flowering, and seed setting following October rains.

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While mortality among all winter legume species has been high as a consequence of the season, serradella survived and responded to October rains.

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Despite 2017 experiencing the second driest six months between April 1 and September 30 since 1900 (118 years) in our central west NSW area, serradella winter legume has outperformed sub clover by a big margin. On some properties biserrula has also performed far better than sub clover.

Sub clover, the traditional winter legume for many districts, more or less totally died off late August early September on ours and many other properties setting a little seed from early maturing varieties but not setting any from mid-season varieties. Late winter early spring was just too dry. 

While mortality among all winter legume species has been high as a consequence of the season, serradella and biserrula, especially on our lighter country, survived in enough quantity to respond to breaking early October rains to regrow, set more seed, fix more soil nitrogen and provide more useful high-quality feed. Ability to root deeper and faster than sub clover is part of the reason why serradella and biserrula survived the long dry better than sub clover. Deeper rooting helps access more soil moisture and nutrients, vital in long dry periods. Also probably important is that both species have better acid soil tolerance than sub clover and with acid subsoils common in many lighter soil paddocks, tolerant varieties are able to better grow in them. While liming has helped correct top soil acidity it has commonly had little impact on subsoil acidity.

Serradella and biserrula also have an inherent ability to regrow, flower and set more seed should they remain alive after a long dry but with a good rain event eventually arriving. Such has occurred this year with breaking October rains occurring in many districts. In contrast sub clover tends to “shut down” when conditions remain dry for too long and commonly are unable to regrow when breaking rains eventually occur.

A totally different season in 2016 for many districts was excessive winter early spring rain with lush winter legume growth occurring. For us and many landholders, especially those running cattle, bloat was an issue. Serradella and biserrula fortunately are largely regarded as bloat free and provided bloat free grazing areas when species including sub clover and medics were causing problems, including animal deaths. A number of serradella and one main biserrula variety have high levels of hard seed, commonly better than that of the best sub clover varieties. Once a good soil seed bank has built up both species are able to regenerate well following short to moderate cropping cycles and/or after a run of droughts resulting in poor seed set. Serradella also has a good range of maturity types ranging from early to mid/late.

Serradella appears to have the ability to perform at maximum or close to full productivity at lower soil phosphate levels than species like sub clover. An ongoing study is testing this thesis across the nation with funding from the Australian Government’s Department of Agriculture and Water Resources as part of its rural research and development for profit program, Meat and Livestock Australia, Dairy Australia, AWI and farmer groups. Research is led by CSIRO and NSW Department of Primary Industries. It is also examining flowering times, hard seededness and seed softening patterns among serradella varieties with the aim of extending the regions in which it can be successfully grown.

Serradella and biserrula are aerial seeders, a major contrast to sub clover which can flower close to the ground and buries a lot of its seed. Grazing that allows good seed set in the initial years and periodically is critical for long term persistence. Many farms, including ours, have serradella as the principal long-term winter legume lasting indefinitely at good density. Serradella has good aphid tolerance (not biserrula). Both species are equal in quality to other legumes and have had few disease issues. Neither has good waterlogged tolerance. 

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