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

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

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

  2. How it all started…… July 1994 Australian newspaper Wanted PhD student to look at biology of Chilean needle grass. Mark’s thoughts *

  3. 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

  4. 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)

  5. 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

  6. Long lived seed bankOne years seeding seven years weeding (10 seeds/ m2 after 12.4 years)

  7. 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

  8. Why I hate CNG • Gets around • Has few friends

  9. 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)

  10. Seed dispersal by sheep

  11. 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

  12. Distribution Current 3 million ha Potential 40 million ha

  13. 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

  14. Landholder views of CNG • 80 % believed CNG has negative economic impacts • 95 % of respondents to survey said CNG is not beneficial

  15. 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!

  16. 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

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

  18. 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

  19. Management options • Depends on land use • High cost • Crop rotation • Pasture sowing • Herbicide control • Slashing/ mechanical control • Low cost • Burning • Biological control • Grazing management *

  20. 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

  21. How to favour desirable pasture species 2 • Increased cost of fencing paddocks and more intensive management

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