On many properties a feature of pasture recovery post drought has been how well many winter legumes have regenerated to provide great winter feed.
Serradella on light acid soils for a few months now has provided high quality low bloat risk feed. Variety choice, previous establishment, previous grazing management and soil fertility have been key aspects. Some stands are decades old with long term persistence despite tough times. Sub clover regeneration has also been excellent as has other species including biserrula (see article The Land page 23, April 9 re Beckom's Mike and Velia O'Hare).
For an example of long term serradella persistence (plus sub clover and biserrula) and good productivity we can provide a morning look around our serradella (Purlewaugh east of Coonabarabran) in tropical and native grass paddocks. All aspects of sowing, variety, grazing management and nutrition will be covered. Due to Covid-19 virus we are unable to hold an open field day. However we can cater for a small group (5 to 10) just contact us to arrange at a gratis rate.
Serradella is our main legume in native and tropical grass light soil pastures. Key aspects are early flowering hard seeded varieties (King, but there are other good ones) and being careful to allow seeding every second or so years. Serradella is an aerial seeder so in dry spring years like the last three, light or no spring grazing until after seed set has been important. In tablelands longer season Avila is suitable.
It has several valuable features including more phosphorus efficiency than other legumes. Research by CSIRO and others, (MLA funding), show serradella performs at maximum production at lower soil phosphorus levels than required for species such as sub clover and medics. For example, on a soil with low "phosphorus buffering index" (PBI) serradella grows at maximum at around 20mg/kg (Colwell test) whereas sub requires 30mg/kg or higher. In the last two years that has saved us thousands of fertiliser dollars.
Serradella is a most acid soil tolerant species in soils with acidity down the profile. Soil aluminium toxicity, assessed as percentage of cation exchange capacity (CEC), correlates with soil pH and adversely affects many species. Serradella varieties generally have high tolerance to aluminium and have produced and persisted in soils as low as pH 4.0.
Especially valuable in a good winter/spring, serradella is low risk for bloat. Our steers are placed on serradella dominant pastures when bloat risk on species like sub clover is high. It roots faster and deeper than legumes like sub clover. Faster rooting helps faster establishment in autumn and can help persistence longer into protracted dry periods, like the recent droughts, where it has commonly survived while others have died. Related to its root attributes is its ability to "re-fire" should later spring rains occur. In contrast species like sub clover often senesce following a dry early spring and fail to regrow in response to later rains.
MLA funded research supports that serradella has few known diseases whereas sub clover is often compromised by various root rots and virus leaf diseases. Yellow serradella has good tolerance to many aphid species whereas sub clover can be badly compromised.
Unlike some varieties of sub clover, serradella does not contain harmful levels of oestrogen that can lead to sheep fertility issues. Serradella feed quality is at least equal to other pasture legumes for grazing, hay, silage or carryover feed.
Production of winter legumes vary according to area and soil type. In acidic deep sandy and sandy loam soils, serradella is often far more productive than species like sub clover. Current research shows mid-maturing variety Avila in newer serradella areas like the southern tablelands can yield high, 10.0t/ha dry-matter.
A well-researched relatively new development is to sow un-processed serradella seed, commonly self-harvested, in summer, with Alosca rhizobia (group S and G) impregnated clay-based granules. Hard seed breaks down over summer and rhizobia impregnated granules survive into autumn. Summer sowing advantages, with untreated "hard-seed", is faster establishment on autumn rains. Serradella is a prolific seed producer.
Next week: Knowing herbicide soil residual life is vital for avoiding future plant damage.
Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or contact 0428 752 149.
