[ASC-media] Decline in canola yields due to 'soil constraints'

joanne.finlay at dpi.nsw.gov.au joanne.finlay at dpi.nsw.gov.au
Tue Dec 19 01:20:05 CET 2006

20 December 2006

Decline in canola yields due to 'soil constraints'

Canola yields in southern Australia decreased by ten percent during the 
1990s, and grain growers fear that acid and saline soils could be partly 
to blame.

Sub-soil constraints on canola performance, along with increased disease 
pressure, are thought to be the two main reasons for the yield decline.

A new three year $900,000 research project funded by the Grains Research 
and Development Corporation (GRDC) is to look at the relative contribution 
of subsurface soil constraints to the poor performance of canola.

Project leader Dr Mark Conyers from the NSW Department of Primary 
Industries (DPI) says the popularity of canola ? invaluable as a 'break' 
crop ? could have led to it being grown on less suitable soils.

A cash crop in its own right, canola is used to break the cycle of cereal 
root diseases and to improve the performance of wheat. 

Research in southern NSW has found that wheat grown after canola yields 20 
percent more than wheat grown after wheat, and the gross margin for 
canola-wheat is 25 percent higher than for wheat ?wheat.

Dr Conyers says increased use of canola could have led to increased 
disease pressure, and that disease is a key factor in yield decline in 
some areas.

"The decline in relative canola performance could also be due to its 
increased popularity in the 1990s and the consequent spread of canola onto 
less suitable soils."

Researchers have found that the depth that canola roots grow to varies 
greatly according to soil type, and this affects how much water the plants 
can access.

A CSIRO survey of 130 paddocks from Corowa to Canowindra in southern NSW 
found that root depth in heavier sodic (sodium-affected) clay soils was 
about 100cm ? half that for friable red loams.

At sowing time, water stored in subsoil can significantly improve yields ? 
and the amount of stored water available to a crop is strongly influenced 
by root depth.

Dr Conyers said research undertaken south of Wagga Wagga found that the 
development of roots of canola plants in about 60% of paddocks were 
severely restricted, often resulting in 'J-rooting'.

The study aims to identify key sub-soil constraints such as hardpans, 
salinity (osmotic effects or toxicity), acidity and sodicity.

"This will enable us to provide 'best bet' management strategies for 
ameliorating sub-soil constraints."

"Our goal is to improve canola performance so that is important role in 
the farming system is maintained", Dr Conyers said.

GRDC has awarded the Graham Centre ? a partnership between NSW DPI and 
Charles Sturt University ? funding to lead a consortium to carry out the 
research. Consortium partners include CSIRO, Farmlink, Victorian DPI and 
the University of Melbourne.

Contact: Dr Mark Conyers, Wagga Wagga, 6938 1830 or 
mark.conyers at dpi.nsw.gov.au. 

Media inquiries: Joanne Finlay on 63913171 or 0428 491813.


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