Weed species richness, density and relative abundance on farms in the subtropical grain region of Australia
L. J. Rew A F , R. W. Medd B , R. Van de Ven B , J. J. Gavin A C , G. R. Robinson D , M. Tuitee E , J. Barnes E and S. Walker DA NSW Department of Primary Industries, Tamworth Agricultural Institute, Tamworth, NSW 2340, Australia.
B NSW Department of Primary Industries, Orange Agricultural Institute, Forest Road, Orange, NSW 2800, Australia.
C Present address: South Australian Department Water, Land and Biodiversity Conservation, PO Box 357, Port Augusta, SA, 5700, Australia.
D Department of Primary Industries, PO Box 2282, Toowoomba, Qld 4350, Australia.
E Primary Industries and Fisheries, PO Box 23, Kingaroy, Qld 4610, Australia.
F Corresponding author. Email: lrew@montana.edu
Australian Journal of Experimental Agriculture 45(6) 711-723 https://doi.org/10.1071/EA03273
Submitted: 20 December 2003 Accepted: 17 September 2004 Published: 29 June 2005
Abstract
Weed management is one of the most important economic and agronomic issues facing farmers in Australia’s grain regions. Weed species occurrence and abundance was monitored between 1997 and 2000 on 46 paddocks (sites) across 18 commercial farms located in the Northern Grain Region. The sites generally fell within 4 disjunct regions, from south to north: Liverpool Plains, Moree, Goondiwindi and Kingaroy. While high species richness was found (139 species or species groups), only 8 species occurred in all 4 regions and many (56 species) only occurred at 1 site or region. No species were observed at every site but 7 species (Sonchus spp., Avena spp., Conyza spp., Echinochloa spp., Convolvulus erubescens, Phalaris spp. and Lactuca serriola) were recorded on more than 70% of sites. The average number of species observed within crops after treatment and before harvest was less than 13. Species richness tended to be higher in winter pulse crops, cotton and in fallows, but overall was similar at the different sampling seasons (summer v. winter). Separate species assemblages associated with the Goondiwindi and Kingaroy regions were identified by correspondence analysis but these appeared to form no logical functional group. The species richness and density was generally low, demonstrating that farmers are managing weed populations effectively in both summer and winter cropping phases. Despite the apparent adoption of conservation tillage, an increase in opportunity cropping and the diversity of crops grown (13) there was no obvious effect of management practices on weed species richness or relative abundance. Avena spp. and Sonchus spp. were 2 of the most dominant weeds, particularly in central and southern latitudes of the region; Amaranthus spp. and Raphanus raphanistrum were the most abundant species in the northern part of the region. The ubiquity of these and other species shows that continued vigilance is required to suppress weeds as a management issue.
Acknowledgments
Many thanks to all of the farmers who collaborated with this project and to John Hosking and Andrew Storrie at Tamworth Agricultural Institute for help with plant identification. The project was funded by the Grains Research and Development Corporation with support from NSW Agriculture. Constructive comments from 2 anonymous referees helped to improve this manuscript, particularly regarding the use of correspondence analysis.
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