Bartolo bladder clover

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Bartolo is the first cultivar of bladder clover (Trifolium spumosum) commercially available to world agriculture. It can be grown successfully across mildly acid to alkaline sandy-loam and loam soils and is suited to regions with 32-500mm annual rainfall. High seed yields from direct use of grain harvesters makes bladder clover a lower cost alternative to subclover and annual medics.

Origin

Bartolo bladder clover was collected from Cyprus (near the town of Melini) in 1987 by C. Francis, D. Drousiotis and A. Della. It has been developed by the Department of Primary Industries and Regional Development with the involvement of research officers Angelo Loi and Bradley Nutt, as part of the National Annual Pasture Legume Improvement Program.

Description and area of use

Bladder clover is a self-pollinating species and produces small pink flowers. Seeds are contained in a papery pod which is surrounded by a bladder-like, papery calyx; the basis for the common name of bladder clover. One inflorescence may produce up to 150 seeds. Individual seeds are round in shape, approximately 2mg in weight, and range in colour from yellow to orange brown.

Bartolo is a semi-erect cultivar, flowering approximately 105 days after emergence in Perth. It is adapted to sandy-loam and clay-loams soils of mildly acid to alkaline reaction (pH 5-8 CaCl2), provided it is reasonably fertile. It is not adapted to saline soils or to long periods of waterlogging.

Bladder clover has an advantage for seed-setting over subterranean clover on hard setting soils, where subterranean clover is unable to bury its burrs. Bartolo can be sown alone or is an ideal companion plant in mixtures with other legumes such as subterranean clover or yellow and French serradellas.

Bartolo flowers
Bartolo flowers

Field performance

The quantity of forage produced by Bartolo is at least equivalent to current pasture such as subterranean clover or annual medics. Peak dry matter yields in ungrazed experimental swards have ranged between 4-7t/ha, depending on season and location. Seed yields are normally high ranging from 0.5-1t/ha. Seed is easily harvested using conventional grain harvesting machinery.

Severe frost at flowering can reduce seed production. Bartolo regenerates well in both continuous pasture and after rotational cropping. It has a hard seed level in the autumn following seed set of about 55%. This suggests that Bartolo has adequate hard seed levels for persistence in crop rotations but also makes it suitable for use in a phase farming system (short pasture phases of 1-3 years). The pattern of seedling emergence of Bartolo indicates it suffers less seedling loss from false breaks following un-seasonal rainfall.

Bartolo dry flower head and seeds
Bartolo dry flower head and seeds

Nutritive value

The feeding value of Bartolo is similar to subterranean clover. Digestibility of Bartolo in spring can be as high as 82%, with 22% crude protein; these values decrease from late flowering to senescence. Grazing trials have shown no differences in liveweight change or wool growth between sheep grazing Bartolo and Dalkeith subterranean clover.

No livestock disorders have been reported with Bartolo but, as with most legumes, very pure bladder clover swards could cause bloat in cattle. Levels of the phyto-oestrogens formononetin (0.015%) and genistein (0.002%) in Bartolo are lower than in Dalkeith subterranean clover and are unlikely to cause infertility problems and difficult births in grazing animals.

Establishment

Bladder clover should be treated as a seed crop in the year of establishment to ensure maximum seed set. Spray-top the paddock in the previous spring or select a paddock coming out of a cereal crop where broad-leaf weeds have been successfully controlled. Delay sowing in high rainfall regions to achieve good weed control with a knockdown herbicide.

In low rainfall regions sow bladder clover as close to the break of season as possible. Inoculation with Group C (strain WSM 1325) rhizobium is highly recommended. Sow from 5-10kg/ha if sown alone. Use lower rates if sown in mixtures with other pasture legumes. For optimal establishment sow bladder clover less than 2cm deep.

If machinery with precise seeding depth is not available this can be accomplished by dropping seed on the surface and covering with trailing harrows. Fertilise at sowing with at least 150kg/ha superphosphate or super-potash, if on sandy soils. Control redlegged earth mite until plants have three true leaves.

Regenerating Bartolo sward
Regenerating Bartolo sward

Herbicides

Bartolo is sensitive to many of the more common broadleaf herbicides including Bromoxynil, Spinnaker® and Raptor®. Broadstrike® appears reasonably safe in the year of establishment and Tigrex® may offer an intermediate weed control option in established pastures.

Management

Moderate grazing six to eight weeks after germination will help reduce weeds and encourage development of a prostate sward. Graze lightly or remove animals during flowering in the establishment year to optimise seed set. Bladder clover seeds are relatively small and a large proportion will survive ingestion by grazing sheep and cattle. Removal of biomass by heavy grazing over the summer is necessary to achieve good regeneration in the second year.

Bartolo under grazing
Bartolo under grazing

Disease and pest tolerance

Redlegged earth mites need to be controlled in the first three weeks after sowing to enable successful establishment. Bartolo will suffer damage from heavy infestations of blue-green and cowpea aphids and lucerne flea. Monitor stands in spring and control if necessary, particularly in the year of establishment. Bartolo has little or no sensitivity to clover scorch disease. Occasional infections of pseudopeziza leafspot have been observed in high rainfall areas.

Dry sward of Bartolo ready to be harvested
Dry sward of Bartolo ready to be harvested

Seed harvesting

Seed of Bartolo can be easily harvested with conventional multi-crop harvesters. Best results are achieved using an open front with a tined reel and crop lifting fingers. This method can result in up to 75% of seed capture. Bladder clover drum settings are similar to those used for wheat but with a reduced wind speed. Short stands of AGWEST® Bartolo can be raked into windrows and collected using lifting fingers or a pickup front.

Seeds are easily handled with augers and elevators and can be cleaned with standard seed processing equipment. Seed coats are much thicker than other pasture legumes and require aggressive scarification to achieve high levels of germination.

Harvesting Bartolo seed
Harvesting Bartolo seed

Production and marketing

Bartolo is a public variety and can be freely bought and sold.

Acknowledgment

Bartolo was developed and field tested as part of the National Annual Pasture Legume Improvement Program supported by the Grains Research and Development Corporation and Australian Wool Innovation.

Contact information

+61 (0)8 9368 3907

Author

Angelo Loi