05-06-2003

Wide-scale tree planting has limited appeal for farmers in the battle against growing salinity, a new economic study jointly funded by the National Dryland Salinity Program (NDSP) and the Grains Research and Development Corporation (GRDC) has revealed.

Although many thousands of farmers indicate they have planted trees to aid salinity management, the area planted nation-wide for this purpose was actually less than that planted to lucerne pastures in 2002.

The study, led by Ross Kingwell, was designed to evaluate farmers options for managing salinity. The research involved 40 case studies by economists and covered areas of WA, SA, New South Wales and Victoria.

It found that despite a general understanding that trees assist in lowering water tables to reduce salinity, the costs and returns associated with most tree plantings were restricting their uptake by farmers.

"According to the Australian Bureau of Statistics, across Australia only three-quarters of a million hectares of trees was planted to combat salinity in 2002, "Dr Kingwell noted.

"Current tree options such as oil mallees are potentially profitable on some broadacre farms. However, in most cropping situations, wide-scale tree planting is often less profitable than crop and pasture options.

"The relatively poor profitability of many trees means many farmers consider planting them only where cropping is not possible or not profitable."

"The serious challenge to researchers and farmers is to establish profitable systems that incorporate areas of trees sufficient to limit recharge, he suggested.

"By 2020 the salt-affected area in the GRDC agro-ecological zones is forecast to grow by 1.1 million hectares to 3.7 million hectares.

"Over 60 per cent of the increase will be in the GRDC Western Region covering some of the nation's major grain production regions. Salinity will impact on the national harvest and affect those regional economies."

The zones likely to be most affected are the WA Sandplain, SA Vic Bordertown Wimmera, NSW Vic Slopes, WA Central and Vic High Rainfall.

The report noted that growing lucerne was a main salinity management option for some farmers.

"In many situations lucerne boosted annual farm profit from $1 to $20 per hectare of arable land," Dr Kingwell said. "But on each farm there is an optimal area of lucerne and planting additional areas will only decrease farm profit.

"By comparison, growing saltland pastures such as saltbush and bluebush, when country had already become saline, only boosted annual profit by $2 to $6 per hectare of arable land."

The researchers found that including deep-rooted perennials in farming systems often boosted farm profit, improved water management and in some cases reduced the rate of spread of salinity. But reduced salinity impacts were often not observed for several years.

Where only small areas of deep-rooted perennials were profitable, their contribution to countering salinity was likely to be minor. With such limited plantings the onset of salinity might be delayed but not prevented.

The economists noted a strong and emerging interest in engineering management of salinity, especially in Western Australia, and predicted that this was likely to increase generally.

Anticipating and reacting to demand for information on the effectiveness of engineering options would be desirable, they said.

"Low cost models that offer reasonable predictions about the extent and spread of salinity on farms and the efficiency and profitability of treatment options would be highly useful," Dr Kingwell suggested.

For further information please contact:

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