A PROJECT to identify the culprits in falling canola yields in NSW has been hampered by a string of poor seasons.
The Grains Research and Development-funded project includes trial sites at Culcairn, Lockhart, and between Albury and Lockhart.
Poor spring rainfall in 2007 and last year has meant the results have been inconclusive.
But NSW Department of Primary Industries project leader Mark Conyers was able to get some results from tests during the early part of the growing season, when rainfall was adequate.
He said while there was a clear response to salinity, there had been no response to sub-surface lime, gypsum or deep ripping.
The studies showed the plants were not sensitive to subsurface acidity and compaction.
Dr Conyers said the results regarding sodicity were ambiguous.
"Last spring and the spring before we ran out of moisture, but that only proved water was a limitation to growth in the canola," he said.
Dr Conyers said fertiliser, nitrogen, lime and sulphur needed to be well managed with canola crops.
He said canola was popular in the 1990s, but average yield had declined 9 per cent.
Because more people were growing it, there was potential for more diseases in the crop, he said.
"Also, farmers were growing it on less-suitable paddocks as they wanted to grow a bigger area," Dr Conyers said. "It used to be grown on the best paddocks."
He said canola might make a comeback in NSW as farmers realised its grazing potential.
CSIRO scientist Susan Sprague is researching how diseases including blackleg and sclerotinia can affect yields.
Dr Sprague said she was concerned the dry seasons might have left growers complacent about the potential impact of disease on canola yield.
"Blackleg can kill seedlings and reduce yield in mature plants," she said.
"In a wet year, sclerotinia can cause canola yield losses of up to 25 per cent, with 40 per cent of plants infected."
