Project objectives

Practical, reliable, predictable and cost effective methods to allow land owners and managers in the upper Murrumbidgee catchment to revegetate with local provenance native grasses through:

• faster germination of seed
• more synchronous germination of seed
• increasing the amount of germinable seed (less wastage)
• developing better strategies for seedling establishment

 

Major Recommendations

Seven locally growing species of grass have been investigated. Excellent progress has been made towards the goals of maximising germination rate and increasing the speed of establishment by optimising storage temperature, selection of appropriate species for the local region, and pre-treatment of seed. The following recommendations can be made for practical revegetation with grasses in the region.

• For sunny positions the easiest species to germinate is Bothriochloa macra, but it is a C₄ grass and spring sowing is probably necessary. Austrodanthonia caespitosa, although it exhibits more dormancy than Bothriochloa macra, is also recommended for sunny positions, and could probably be sown in either spring or autumn.
• In semi-shade or moister positions Ehrharta stipoides is the most reliable species and can probably be used for either spring or autumn sowing. The second choice would be Joycea pallida. The latter is a more tussocky grass.
• Bothriochloa macra, Austrodanthonia caespitosa, Ehrharta stipoides and Joycea pallida could all be amenable to having their seed coats removed by suitable machinery before sowing which will increase the speed of germination and establishment.
• For sunny positions Austrostipa scabra can be used if storage has been managed properly, but it is more difficult than Bothriochloa macra and Austrodanthonia caespitosa. Poa labillardierei, for semi shade positions, also needs careful management.
• Themeda triandra can not be recommended for reliable establishment, although recent improvements in harvesting and cleaning techniques may well improve its performance. Further work is needed on this species.
• A potentially useful strategy would be to develop seed mixes that include the more difficult species as well as the easier ones. This would increase diversity in the sward and allow the difficult species to germinate opportunistically.
• Additional trials are recommended on the use of fertilisers, machinery for seed cleaning and seed coat removal, the use of herbicides to control weeds, and seed production under irrigation.
• Opportunities exist to develop seeds that are coated with germination enhancing chemicals. Coated seeds should also be less susceptible to predation

 

Summary of results and recommendations

Seed testing in vitro

• predictable germination rates will only be possible if seed of known provenance is used, or germination tests are done for each seed batch
• seed quality can be estimated in most species by soaking in water followed by microscope examination
• standardised conditions should be used for in vitro testing
• the use of towelling rather than filter paper is more labour efficient for in vitro testing
• the use of PPM, Previcur or Foli -R-Fos is recommended for in vitro testing to control bacteria and fungi
• powder formulations such as Thiram may be more appropriate for field application because of its ease of use
• fungicides must not be used in combination with Trichopel (see below)
• incubation should generally be at room temperature
• the ‘International Rules for Seed Testing’ (International Seed Testing Association, 1996) are recommended as a guide to standard practice for evaluating germinability

Seed supply and quality

• predictable germination rates will only be possible if seed of known provenance is used and germination tests are done for each seed batch
• seed of some species may require storage at lower temperatures to insure against poor seasons for seed production. The lower temperature will slow seed ripening
• seed quality can be estimated in most species by soaking them in water followed by microscope examination
• some of the reported findings of low establishment rates for native grass seed may be due to sowing less seed than was assumed
• sowing rates will probably need to be increased compared to past practice for most species to compensate for deficiencies in seed quality and quantity
• mechanised harvesting does not appear to reduce seed quality and has obvious benefits for the supply of large quantities of seed
• mechanised cleaning can be used to select only full seed

Storage temperature

• seed of most species can be stored at room temperature, but ripening of the seed in some instances requires several months before germination rates will be satisfactory (in practical terms this usually means that seed collected in summer should be used in the following spring)
• seed of all species can be stored at room temperature (20-25° C) for convenience and low cost
• Bothriochloa macra and Ehrharta stipoides showed very little or no dormancy and only require minimal monitoring of germinability. Surplus seed of these species remains viable for at least 2 years at room temperature
• dormancy will prevent the early use of intact Poa labillardierei seed
• Joycea pallida preferably should be used within a year of harvesting or after 2 years of storage
• Themeda triandra shows strong dormancy and is very unpredictable in its responses. It will require constant monitoring to judge when it is ready to use
• Austrostipa scabra should be stored at room temperature and sown, assuming harvest in mid-summer, in the following spring or after 2 years storage
• Austrodanthonia caespitosa is intermediate in its dormancy responses. Monitoring of germination rates will be beneficial to optimise the rate of establishment but may not be necessary if seed is plentiful as germination rates were moderately high

Physical pre-treatment

• removal of the seed coat is beneficial for Austrodanthonia caespitosa, Bothriochloa macra, Ehrharta stipoides, Joycea pallida, and Themeda triandra, although often this meant faster germination rather than greater % germination and the effect in some cases depended on the age of the seeds
• although Austrostipa scabra and Poa labillardierei benefited from seed coat removal this is probably not practical
• the technology needed to remove seed coats needs further investigation
• none of the other physical pre-treatments tested (vernalisation, wet/dry cycle, heat and seed orientation) stimulate Themeda triandra germination significantly and some were detrimental
• light probably does not influence dormancy in Austrodanthonia caespitosa, Austrostipa scabra, Joycea pallida and Themeda triandra (the other species were not tested)
• Themeda triandra seed appears to be damaged by UV light so it should probably be buried when sown

Chemical pre-treatment

• smoke treatment is generally not necessary, though it may be useful to break dormancy in fresh seed of some species
• smoke treatment should be used on fresh seed of Austrodanthonia caespitosa, Austrostipa scabra and Joycea pallida to accelerate and increase germination rates. Smoke is not necessary with older seed of these species
• smoke has no effect on Bothriochloa macra, Ehrharta stipoides, Poa labillardieri (young seed not tested) or Themeda triandra
• Trichopel, gibberellic acid and tissue culture medium all enhanced germination of Themeda triandra
• boric acid, PPM and potassium nitrate had no significant effects on germination of Themeda triandra
• concentrated hydrochloric acid had a strongly negative effect on Themeda triandra germination
• smoke extracts and Trichopel can easily be incorporated in seed mixes when sowing
• gibberellic acid and elements from the tissue culture medium (as well as smoke extracts and Trichopel) could be incorporated into pelletised seed

Field trials

• kerosene is not recommended as a suitable ant deterrent as it reduced in germination of Themeda triandra seed.
• burial of seed is likely to reduce predation, and will also prevent UV damage and maximise germination of Themeda triandra
• sowing a C₃ grass such as Austrodanthonia caespitosa in autumn should provide a reliable revegetation method providing there is appropriate weed control
• further trials using germination enhancing practices suggested in this report are strongly recommended

Austrodanthonia caespitosa

• 100% germination rates can be achieved in 4 days given suitable conditions
• mechanical methods to remove the seed coats need to be investigated
• store seed at room temperature for convenience
• monitoring of germination rates is beneficial to optimise the rate of establishment but may not be necessary if seed is plentiful
• remove the seed coat prior to germination to accelerate establishment
• use smoke treatment on fresh seed to accelerate and increase germination rates
• smoke is not necessary with older seed

Austrostipa scabra

• germination rates of nearly 90% have been achieved in 5 days under suitable conditions
• store at room temperature and sow, assuming harvest in mid-summer, in the following spring or wait for 2 years before sowing.
• sow intact seed
• use smoke treatment with fresh seed
• smoke treatment is not needed with older seed

Bothriochloa macra

• 100% germination can be achieved in 3 days given suitable conditions
• store at room temperature
• removal of the seed coat will increase the speed of establishment
• use Bothriochloa macra to establish groundcover quickly in sunny positions ( it does not appear to compete well in the longer term and mixed sowings with other species may be appropriate)
• store at room temperature for convenience and low cost
• surplus seed can be used in the following year
• smoke treatment is not needed

Ehrharta stipoides

• 100% germination can be achieved in 4 days given suitable conditions
• store at room temperature
• use this species for rapid groundcover in semi shade locations
• surplus seed can be used in the following year with adequate rates of germination
• remove the seed coat with young seed to increase the rate of germination
• smoke is not needed

Joycea pallida

• 90% germination can be achieved in 5 days given suitable conditions
• fresh seed can be used for rapid ground cover in semi-shade
• store at room temperature
• remove the seed coat from young seed for rapid germination
• use smoke with fresh seed
• smoke is not needed with older seed

Poa labillardierei

• 100% germination can be achieved in 5 days given suitable conditions
• store at room temperature for convenience
• dormancy will prevent the early use of intact seed
• if possible remove the seed coat
• smoke is not needed with older seed

Themeda triandra

• sometimes 65+% germination can be achieved in 5 days, but usually it is much lower and very unpredictable
• provenance is an important factor in germination characteristics
• kerosene is not recommended to reduce predation as it caused a reduction in germination.
• although storage at room temperature gave the best results further research is needed on this species before specific recommendations can be made
• removal of the seed coat improves germination
• scarification increases the speed of germination but not the ultimate %
• seed appears to be damaged by UV light so it should probably be buried when sown, but more research is needed
• vernalisation reduced germination
• a short wet/dry cycle had no effect but needs further investigation
• heat had no effect
• seed orientation had no effect
• smoke is not needed
• boric acid had no effect
• ‘Trichopel’ increased rate and ultimate % germination
• ‘PPM’ did not enhance germination
• gibberellic acid increased germination
• potassium nitrate had no effect
• germination on tissue culture medium increased germination substantially
• concentrated hydrochloric acid does not substitute for physical scarification

 

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