Publication Date

1993

Description

Viability of large and successful sown pasture development on the wet tropical coast of eastern Australia is threatened from invasion of these pastures by unpalatable grass and legume weeds. The main threats discussed are invasion by the unpalatable grass weeds Sporobolus diandrus (tussocky sporobolus) and Sporobolus pyramldalis (giant rat's tall grass) and the unpalatable, annual legume weed Senna obtusifolia (sicklepod). Specific cases of invasion and suggested causes for the problems are discussed. The major causes· suggested for pasture decline and invasion by less productive weedy species are: disease that can suddenly wipe out an otherwise well adapted species; inappropriate sown pasture species selection for the particular soil, climatic or weed situation; failure to ·act quickly and decisively to eradicate weed species as soon as they appear and before soil seed reserves build up; over-utilisation (over-grazing) of sown species creating a situation where less palatable species gain the advantage to establish and spread; failure to adjust stocking rate annually in line with summer growing season pasture dry matter growth and lack of knowledge or experience by producers of the principles of pasture growth; pasture management and assessment of pasture condition whereby stocking rate is judged on animal condition alone without including an assessment of the condition of the pastures.

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Case Studies and Causes of Weed Invasion of Sown Pastures on the Wet Tropical Coast of Eastern Australia

Viability of large and successful sown pasture development on the wet tropical coast of eastern Australia is threatened from invasion of these pastures by unpalatable grass and legume weeds. The main threats discussed are invasion by the unpalatable grass weeds Sporobolus diandrus (tussocky sporobolus) and Sporobolus pyramldalis (giant rat's tall grass) and the unpalatable, annual legume weed Senna obtusifolia (sicklepod). Specific cases of invasion and suggested causes for the problems are discussed. The major causes· suggested for pasture decline and invasion by less productive weedy species are: disease that can suddenly wipe out an otherwise well adapted species; inappropriate sown pasture species selection for the particular soil, climatic or weed situation; failure to ·act quickly and decisively to eradicate weed species as soon as they appear and before soil seed reserves build up; over-utilisation (over-grazing) of sown species creating a situation where less palatable species gain the advantage to establish and spread; failure to adjust stocking rate annually in line with summer growing season pasture dry matter growth and lack of knowledge or experience by producers of the principles of pasture growth; pasture management and assessment of pasture condition whereby stocking rate is judged on animal condition alone without including an assessment of the condition of the pastures.