The capeweed content of pastures in south-west Western Australia

Abstract

The capeweed (Arctotheca calendula) content of pastures in the agricultural areas of Western Australia was estimated from coloured aerial photographs taken during flowering. Linear regressions were obtained between a visual score for capeweed content based on colour and the actual capeweed content of calibration sites. Surveys in 1972, 1973 and 1975 showed that 1973 was a year of high capeweed content in all areas compared with 1972 and 1975. The content was higher in lower-rainfall wheatbelt areas, where it averaged about 50% of pasture dry matter in 1973, than in the high-rainfall grazing areas, where the average was 37%. Fluctuations from year to year were followed on fixed sites between 1973 and 1977. The high rainfall sites varied more from year to year in capeweed content than did the low-rainfall sites. A detailed survey of one farm was made between 1972 and 1976 and this confirmed the indications from the other broadscale surveys that 1973 and 1976 were years that favoured capeweed. They were years when germination was followed by a 4-5 week dry period. Soil type and position in the landscape were also shown to influence the capeweed content of pastures.

Discrimination of blackberry (Rubus fruticosus sp. agg.) using hyperspectral imagery in Kosciuszko National Park,NSW, Australia

“…The potential of remote sensing to identify and monitor weed infestations has been studied using aerial photography (Arnold et al, 1985;Everitt et al, 1996), multispectral imagery, such as Landsat Thematic Mapper (Dewey et al, 1991;Gardiner et al, 1998;Taylor, 1990) and multispectral digital video systems (Lamb et al, 1999;Lass and Callihan, 1997;Richardson et al, 1985) with mixed success (McGowen et al, 2001). In particular, Ullah et al (1989) and Frazier (1998) showed that high-spatial-resolution multispectral data could be utilized to produce accurate maps of blackberry distribution.…”

Effect of temperature on germination and early growth of subterranean clover, capeweed and Wimmera ryegrass

“…The botanical composition of annual pastures varies markedly from year to year depending on rotation, cultivation, management, environmental conditions at seed set and the timing of the break of season (Arnold et al ., 1985; Arnold and Anderson, 1987; Bolger et al ., 1995; Thomson et al ., 1998). The Mediterranean‐type climate of south‐western Australia is characterized by hot dry summers and cool wet winters (Turner, 1992).…”

The use of qualitative airborne multispectral imaging for managing agricultural crops - a case study in south-eastern Australia

“…Harris and Haney 1973), and later extended to detect weeds in crops and pastures (Barrett and Leggett 1979;Arnold et al 1985). However, limitations of aerial photography for crop monitoring include the absence of a quantitative data acquisition capability, the high cost and limited availability of colour infrared film and processing, and the requirement for manual scanning or digitising for incorporation into a Geographic Information Systems (GIS) package.…”