Degradation in soil quality is major problem in cotton-based farming
systems of Australia, and in particular, the river valleys of north-western
New South Wales (semi-arid climate, cracking clay soils inc. Vertisols)
where a major proportion of Australia's cotton is produced. In general,
corresponding yield decreases can be of the order of 10-30%, although in
extreme cases yield losses of >90% can occur. Management systems whereby
such degradation can be ameliorated and avoided are, therefore, of primary
interest to many cotttongrowers and State Organizations as even a yield
decrease of 10% represents a loss of $42.9 million (based on 1993 values)
to the State of New South Wales. Past research has indicated several
possible management techniques such as minimum tillage and sowing rotations
for avoiding and ameliorating soil degradation in irrigated farming systems
(in cracking clays).
More recently, although surveys, consultations with individual
cottongrowers and cottongrower organizations have indicated a widespread
interest in utilizing combinations of minimum tillage and rotation systems
to combat degradation in soil quality, a major bottleneck in their
extension (particularly cereal rotation crops) to the industry is in
managing/disposing of the large amounts of rotation crop residues under
minimum tillage (in irrigated farming systems in cracking clay soils, inc.
Vertisols). Comments made by cottongrowers at a series of workshops in
November 1994 further indicated that little was known about (a) the "best"
existing method of residue management; eg. burning, incorporation etc., and
(b) the effects of these residue management systems on on-farm and and
off-farm soil and water quality.
We are planning to submit a proposal for an on-farm based project which
will address some of these issues in irrigated farming systems. The
research team includes soil physicists, a soil chemist, a soil
microbiologist, 2 on-farm extension agronomists, a weed scientist and an
economist. I would like to hear from any member of the group who is
currently working or has any past research experience in the area of crop
residue management in irrigated soils (particularly irrigated cracking clay
soils) with a view to initiating a discussion on the subject.