The influence of nitrogen level, rainfall, seed pools and pasture biomass on the botanical composition of annual pastures
1987
Arnold, G.W. (Commonwealth Scientific and Industrial Research Organization, Midland (Australia). Div. of Wildlife and Rangelands Research) | Anderson, G.W. (Commonwealth Scientific and Industrial Research Organization, Wembley (Australia). Div. of Animal Production)
A pasture that had declined in content of Trifolium subterraneum to 5 percent remained at this level over five years when receiving 100 kg per ha of nitrogen fertilizer. On plots not receiving nitrogen fertilizer, but grazed to the same level, Trifolium seedling numbers in autumn increased from 5 per sq cm to a maximum of 60, but Trifolium content of the pastures in October only increased to 15 percent. At another site, where plots were resown to Trifolium, after three years Trifolium content had declined markedly. It had been replaced by Arctotheca calendula. Plots sown to Arctotheca and Erodium botrys maintained high levels of the sown species. Plots sown to the grass Lasiochloa echinata developed a progressively higher content of Arctotheca. Whilst seedling number in autumn was a major determinant of the content of a species in the pastures in August, Trifolium content was enhanced by high autumn rainfall and low winter biomass. The pasture composition in October was mainly determined by composition in August, although heavy rain in October favoured Arctotheca and light rain favoured the grass species.
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