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A 10 year love-hate relationship with CNG: lessons learnt Mark Gardener EWL Sciences, Darwin, NT. How it all started……. July 1994 Australian newspaper Wanted PhD student to look at biology of Chile an needle grass. . Mark’s thoughts. *. Why I love CNG.

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A 10 year love-hate relationship with CNG: lessons learnt Mark Gardener EWL Sciences, Darwin, NT

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A 10 year love-hate relationship with CNG: lessons learntMark GardenerEWL Sciences, Darwin, NT


How it all started……

July 1994 Australian newspaper

Wanted

PhD student to look at biology of Chilean needle grass.

Mark’s thoughts

*


Why I love CNG

  • Has an attractive weeping habit with sexy purple glumes

  • Likes to have sex

  • Is good with kids

  • Will stick around through good and bad times


Reproductively successful

  • Can produce 20,000 seeds/ year/ m2

  • Has 3 types of breeding systems

    • Panicle seeds (cross and self fertilised)

    • Stem seeds (self or cleistogamous)

    • Basal seeds (self or cleistogamous)


1996

1997

Basal node

0.2

0.5

2nd node

1.5

0.9

3rd node

3.1

2.7

4th node

2.5

3.1

Total cleistogene seeds

7.3

7.2

Total panicle seeds

26.6

27.4

Seeds per tiller


Long lived seed bankOne years seeding seven years weeding

(10 seeds/ m2 after 12.4 years)


Long lived tussocks

  • Seedling survival is high

  • Growth is slow but steady even in dry times

  • Survival of tussocks is high - 70% over 3 years


Why I hate CNG

  • Gets around

  • Has few friends


Good dispersal mechanisms

  • Barbed seeds adhere to clothing, machinery and animals

  • e.g. 10 % of seeds still in sheep’s wool after 3 months

  • Wind dispersal up to 3 m

  • Hygroscopic awn (self drilling seed)


Seed dispersal by sheep


Widely dispersed

  • Found over approximately 3 million ha in Queensland, NSW, Victoria, South Australia and Tasmania

  • Found on all land tenures in grassland and open woodlands

  • Tolerates some shade but doesn’t like waterlogging


Distribution

Current

3 million ha

Potential

40 million ha


In summary…

  • CNG is widespread and well established in Australia

  • It is highly persistent and well suited to temperate Australia’s variable climate

  • Its biology mitigates against control at a broad scale


Landholder views of CNG

  • 80 % believed CNG has negative economic impacts

  • 95 % of respondents to survey said CNG is not beneficial


Cost of CNG

  • Cost of control estimated at $60-$120/ ha/ year

  • Returns for grazing/cropping enterprises $24- $112 ha/ year

  • Probable negative return plusongoing cost because of reinfestation!


Benefits of CNG:what I learnt in South America

  • CNG is widespread in temperate grazing regions

  • CNG often the dominant species in temperate grasslands

  • CNG was considered a beneficial winter growing pasture species


What I learnt in AustraliaCNG as a pasture plant in Northern NSW


My view of CNG

  • Yes it does have negative economic impacts

  • But MAYBE it could be used as a pasture species even though there is a drop in production

  • Grazing management may result in more productive outcomes


Management options

  • Depends on land use

  • High cost

    • Crop rotation

    • Pasture sowing

    • Herbicide control

    • Slashing/ mechanical control

  • Low cost

    • Burning

    • Biological control

    • Grazing management *


How to favour desirable pasture species 1

  • A short duration- high grazing intensity- long rest system

  • All species are eaten/trampled to similar height during grazing period

  • During rest (up to 90 days) faster growth of desirable pasture species results in competitive advantage


How to favour desirable pasture species 2

  • Increased cost of fencing paddocks and more intensive management


Conclusion

  • Don’t get emotionally involved with CNG but look for ways to manage it appropriately for your land use


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