25-01-2002

A major study into Queensland's cropping lands conducted by the Queensland Department of Natural Resources and Mines with the support of the Grains Research and Development Corporation has shown the need for targeted management of major areas of cropped land to avoid the threat of dryland salinity.

While salinisation was not generally detected in these areas, 21 per cent, or 500,000 hectares, of the 2.3 million ha of cropping land in Queensland was identified as having a high risk of developing salinity over the next 50 years.

The study found that 1.6 million ha of cropping land required special management to help stop the high salinity hazard land from becoming salt affected.

The Department of Natural Resources Principal Project Officer, Ian Gordon, said the study, entitled 'Delineation of potential salinity hazard areas in Queensland cropping lands' was carried out under the National Dryland Salinity Program and with the co-operation of the Grains Research Development Corporation.

"The study used Geographic Information System-based hazard mapping and EM31 soil conductivity measurements to identify land with a high potential for developing salinity, Mr Gordon said.

"This approach considered land in the context of the contributing catchment areas and found that a significant proportion of the landscape will require 'management' to minimise the risk of salinity developing in those areas identified as being of high hazard," he said.

Mr Gordon said that the PERFECT model (Productivity, Erosion and Runoff Functions to Evaluate Conservation Techniques) was used for Dalby, Goondiwindi, Emerald and Roma to look at the deep drainage potential for six different cropping systems:

• Wheat;
• Sorghum;
• Dryland and irrigated cotton
• Wheat/sorghum opportunity cropping; and
• Wheat/sorghum opportunity with Zero tillage.

"For comparison, simulations of pasture and tree systems were modelled at the same locations, using 43 years of climate data," he said.

"The study re-emphasised the point that, in Australia, broad acre cereal crops and traditional pasture species do not make full use of available soil moisture, allowing more water to be lost through drainage beyond the root zone, nor do they tolerate salt accumulation in the root zone.

"When water tables are close to the surface (less than 2 m deep), total crop loss can occur, with significant reductions in yield when water tables are at about 4 m depth."

Mr Gordon said that assessment by the National Land and Water Resources Audit show that dryland salinity from shallow water tables potentially threatens production from 4.6 million ha of agricultural land Australia-wide and this figure is expected to at least double by 2050 under current climate and land use."

"The report concluded that salinity was an issue in all of Australia's agricultural lands.

"Loss of productive land to saline outbreaks will put more pressure on the remaining unaffected lands.

"Development of management and remediation and innovative farming system strategies is vital to ensure sustainable production is maintained in the long term," Mr Gordon said.

"The main aim is to make full use of available soil moisture, for example by double or opportunity cropping, and using perennial pasture species in rotation with annual crops. In this way, farmers can increase profit and reduce recharge, a real win-win".

For further information please contact:

Please contact Land & Water Australia
Email: land&wateraustralia@lwa.gov.au
Phone: 02 6263 6000