A survey of management and economic impact of weeds in dryland cotton cropping systems of subtropical Australia

Abstract

In dryland cotton cropping systems, the main weeds and effectiveness of management practices were identified, and the economic impact of weeds was estimated using information collected in a postal and a field survey of Southern Queensland and northern New South Wales. Forty-eight completed questionnaires were returned, and 32 paddocks were monitored in early and late summer for weed species and density. The main problem weeds were bladder ketmia (Hibiscus trionum), common sowthistle (Sonchus oleraceus), barnyard grasses (Echinochloa spp.), liverseed grass (Urochloa panicoides) and black bindweed (Fallopia convolvulus), but the relative importance of these differed with crops, fallows and crop rotations. The weed flora was diverse with 54 genera identified in the field survey. Control of weed growth in rotational crops and fallows depended largely on herbicides, particularly glyphosate in fallow and atrazine in sorghum, although effective control was not consistently achieved. Weed control in dryland cotton involved numerous combinations of selective herbicides, several non-selective herbicides, inter-row cultivation and some manual chipping. Despite this, residual weeds were found at 38–59% of initial densities in about 3-quarters of the survey paddocks. The on-farm financial costs of weeds ranged from $148 to 224/ha.year depending on the rotation, resulting in an estimated annual economic cost of $19.6 million. The approach of managing weed populations across the whole cropping system needs wider adoption to reduce the weed pressure in dryland cotton and the economic impact of weeds in the long term. Strategies that optimise herbicide performance and minimise return of weed seed to the soil are needed. Data from the surveys provide direction for research to improve weed management in this cropping system. The economic framework provides a valuable measure of evaluating likely future returns from technologies or weed management improvements.

Measuring the effectiveness of management interventions at regional scales by integrating ecological monitoring and modelling

“…Arable weeds are a worldwide problem for crop production and are costly in terms of yield reductions, in addition to the financial costs of the machinery and chemicals needed to control them –. Moreover, there are indirect costs associated with weeds; for example, some rotational or management combinations are not possible when weeds are an established problem.…”

Acute toxicity and sublethal effects of the mixture glyphosate (Roundup® Active) and Cosmo-Flux®411F to anuran embryos and tadpoles of four Colombian species

“…Toxicity values were estimated through the mean lethal concentration (LC 50 ) and the associated 95% confidence intervals, using the TSK Trimmed SpearmanKarber method (version 1.5). Sublethal effects at 96h were assessed by measuring the tadpole body size, the stage of embryonic development, and the tadpole swimming performance, as this is expected to relate the ability to evade predators (Fitzpatrick, Reisen, & McCaslin, 2003;Walker et al, 2005). Twenty surviving animals, and ten animals for the laboratory experiments with tadpoles, were tested from the control and each of the tree experimental concentrations lower than the LC 50 .…”

Curvas de dose-resposta e eficácia de herbicidas inibidores da enzima ALS aplicados em pré-emergência sobre espécies de Amaranthus

“…Reconhecendo-se o potencial de prejuízo à cultura do algodoeiro, atualmente espécies de Amaranthus são consideradas problema em campos de produção de algodão no Paquistão (Bukun, 2005), na Austrália (Walker et al, 2005) e nos Estados Unidos (Troxler et al, 2002;Porterfield et al, 2003;Murdock et al, 2004;Richardson et al, 2007). No Brasil, estas espécies ocorrem em todos os Estados, com maior concentração em regiões agrícolas (Kissmann e Groth, 1999).…”