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Charles Sturt University (2010)

Low cost rehabilitation of perennial grass pastures by managing seedling recruitment

Thapa, Roshan

Titre : Low cost rehabilitation of perennial grass pastures by managing seedling recruitment

Auteur : Thapa, Roshan

Grade : Doctor of Philosophy (PhD) 2010

Université de soutenance : Charles Sturt University

Résumé
Many permanent pastures across southern Australia have sub-optimal levels of perennial grass species, below that required for sustainability. However, increasing perennial grass content by conventional re-sowing is often unprofitable. Research in central New South Wales, with the native grasses, wallaby grass (Austrodanthonia spp.) and red grass (Bothriochloa macra), has identified low-cost, ecologically-based management options to enable the successful recruitment of native perennial grass seedlings within existing pastures. Successful recruitment occurs in early autumn, provided the following conditions are met : (i) adequate quantities of germinable seed are available (following removal of stock from spring to promote flowering and seed set) ; (ii) a suitable rainfall event after seed maturation and shedding results in a 7-15 day period of moisture in the top 50 cm of soil ; and (iii) an appropriate micro-site is present for seedling emergence (light scarification can help on soils that are not self-mulching). Insecticides can be used to control seed-harvesting ants and sub-lethal herbicide doses can be used at seed maturity to weaken plant competition prior to recruitment. Climate analyses indicated that soil moisture conditions in February-March should be favourable for seedling recruitment in most years. These results have been used to develop a management package for farmers to enhance the recruitment of desirable perennial grass seedlings within existing pastures. The techniques can be used to significantly increase the perennial grass content of pastures across south-eastern Australia at low-cost, with substantial impacts on medium to long-term profits and environmental benefits.

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Page publiée le 24 mai 2011, mise à jour le 10 juillet 2017