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Impact of pasture height and herbage mass on suppression of variegated thistle in North Island East Coast hill country

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posted on 2023-05-10, 07:38 authored by Katherine TozerKatherine Tozer, Rose GreenfieldRose Greenfield, Renee Grigson, Catherine CameronCatherine Cameron, Ants Roberts, Emma NoakesEmma Noakes, Tim Rhodes, Sue ZydenbosSue Zydenbos
Variegated thistle in East Coast North Island hill country reduces pasture and livestock productivity. To quantify the impact of increasing amounts of pasture cover (herbage mass) on this weed, variegated thistle seeds were hand-sown in autumn into pasture swards that ranged in height from 0 cm (bare ground) to 12 cm, on an East Coast property near Gisborne. Sward height was maintained by mowing without damaging the thistle plants. Increasing pasture cover reduced thistle emergence, height, diameter, biomass, survival, and seed production. By early June, 7 weeks after sowing, thistle emergence was greatest from bare ground and from maintaining a pasture at a height of 3 cm (>1100 kg DM ha-1 in autumn) and declined with increasing pasture height. By December, thistle height, diameter, biomass, flowerhead production and survival were highest in the bare ground treatment (thistle biomass ≈760 g plant-1), much lower in the 3-cm pasture height treatment (≈20 g plant-1), negligible in the 6-cm (>1600 kg DM/ha) and nil in the 8-cm (>1800 kg DM ha-1) and 12-cm (>2700 kg DM ha-1) pasture treatments (P<0.002). Maintaining pasture height of 3 cm severely reduced variegated thistle establishment, growth and flowerhead production. Results infer that grazing management strategies, such as lengthening the interval between grazing events in autumn and early winter, will increase pasture cover and are likely to severely reduce thistle establishment, growth and seed production.


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This work is licensed under a Creative Commons Attribution-Non Commercial-NoDerivatives 4.0 International License.


  • English

Does this contain Māori information or data?

  • No


NZ Grassland Association Inc.

Journal title

Journal of New Zealand Grasslands




Tozer, K. N., Greenfield, R., Grigson, R., Cameron, C., Roberts, A., Noakes, E., … Zydenbos, S. (2020). Impact of pasture height and herbage mass on suppression of variegated thistle in North Island East Coast hill country. Journal of New Zealand Grasslands, 82, 83–90. doi:10.33584/jnzg.2020.82.439

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