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.