Professor Jim Pratley, Dr Deirdre Lemerle,
Dr Terry Haig
Research Staff:
Mr Sean Cormack
Funding:
$80,000 (GRDC)
Duration:
1997-1998
Project Summary:
Herbicides are an essential component of crop production in Australia. Nearly $500 million are
spent each year on herbicides on Australian farms to
raise the productivity and quality of the primary product.
The increasing environmental demands on farmers, together with the need to reduce moisture
loss through evaporation, have resulted in stubble
retention systems being increasingly adopted on farms of
the winter rainfall areas of southern Australia.
In these areas, however, the dry summers
frequently experienced in the south often do not allow for
the leaching and breakdown of stubbles. Thus, at
sowing time, leachate from the stubbles may interfere with
the crop germination and establishment process.
The leachate may contain allelochemicals and also herbicides stored in the stubbles from the
previous year's application. Anecdotal evidence from
farmers indicates a significant problem can occur in
some situations and preliminary evidence (Pratley, 1992)
has demonstrated that chemicals do carry through
in stubbles.
There is therefore an important need to better understand the processes involved and the factors
of influence so that management practices can be put
in place to minimise its effects. Further, such
carryover may also play an important role in the development
of herbicide resistance through continuous exposure
of the same herbicide to potentially resistant weeds.
Further, the possibility that at least some chemical
may be stored in the grain puts at risk the export
markets serviced by the Australian grain industries.
The aims of the project are to:
• clarify the extent to which herbicides are stored
in stubbles and in grain;
• evaluate the extent of variability between
varieties and species in their abilities to store chemicals;
• investigate the influence of environmental
factors on the potency of crop stubbles with respect
to herbicide carryover.
