Abstract:
This project provided valuable review of environmental impact and development of
risk assessment strategies within the Australian Cotton Industry. It was found that
GM technologies can reduce potential environmental impact by reducing or
changing pesticide use practice. Although the benefits of Bt cotton varieties and
reduced endosulfan use are well documented, a strong correlation between pesticide
use (per ha) and average rainfall was observed. This indicates that climatic
conditions offer a potential predictor of environmental impact. These results are
based on the assumption that insect pressure is greater during wetter periods, thus
requiring more insecticide use. We would therefore expect to observe an increase in
pesticide use and environmental impact when growing conditions improve,
commensurate to the use of Bollgard cotton within the industry.
Analysis of environmental impact of herbicide use did not show a significant
reduction associated with the introduction of Roundup Ready (RR) cotton. These
results indicate that improvements in herbicide use scenarios could potentially have
been made by reduced use of "high impact" residual herbicides with introduction of
RR cotton but this did not occur. However, the use of RR Flex and Liberty Link
cotton may improve the potential environmental impact of herbicide use if such
reductions in use of residuals is achieved. We also identified a slight negative trend
(r2=0.3) between herbicide application and precipitation. This indicates that if the
climates become drier then an increase in herbicide use (g/ha) will be observed. We
expect this was either a response of growers, aiming for a higher level of crop
protection for improved yields or reducing the risk of crop failure, or a more virulent
response by weeds during dry periods. The results of the analyses conducted within
this project were used to direct industry goals with respect to environmental
custodianship.
An experiment conducted within this project showed that pesticide residues
dissipate faster in actively composted cotton gin trash (GT) than in passively
composted GT. This experiment evolved from a previous study concerning potential
environmental exposure and the regulation of GT wastes. Whilst composting of GT
is recommended to reduce the concentration of pesticide residues, the resources
required may be too large for an effective BMP. Further studies, with respect to reuse
of GT, are more likely to identify a more suitable industry-wide management
practices.