Water-saving study yields high hope for farmers

Thursday, 10 July 2003

At a time when water is becoming a more highly valued commodity, research by the University of Adelaide shows Australian farmers can potentially save water on crops without losing profits - and at the same time, increase their yields.

It's all thanks to the use of an organic compound known as polyacrylamide, which can reduce excessive leaching of water through sandy soils.

Polyacrylamides are long chain carbon molecules that can alter the behaviour of water in soil, acting like a "sponge" to soak up water more effectively and hold it in place in the soil.

Polyacrylamide can be added to irrigation systems in the form of a fine powder, which dissolves into irrigation water at the point of delivery.

Shane Phillips has been studying polyacrylamide use for several years. Mr Phillips is now studying for his Masters in Applied Science at the University of Adelaide's School of Earth & Environmental Sciences.

"Effectively, by adding polyacrylamides to the irrigation process we can increase water retention in the root zone of sandy soils where the water is needed most, and reduce the frequency of irrigation, thereby saving water. At the same time, the technique is able to increase plant yields," Mr Phillips says.

"Considerable success in using these organic compounds has been demonstrated overseas, and our experience in Australia is also extremely positive."

Mr Phillips has studied the practical results of polyacrylamide usage in drip irrigation in Australia, such as in vineyards.

"In drip systems the use of polyacrylamide has increased water retention in sandy soils in the top 40cm of the root zone," he says.

"In a vineyard trial this season, this resulted in a marked difference for a crop at Lake Cullularaine in north-west Victoria. The rows of vines that were not treated with polyacrylamide showed visually more leaf burn than those that had been treated, and the yields from the treated area were also higher.

"This trial has been expanded into Viognier and Shiraz as part of the postgraduate research program."

Because of their ability to retain water, polyacrylamides also help to prevent other problems of irrigation, such as the need for "back flushing" by increasing the amount of clay removed from within the drip line, Mr Phillips says.

"Back flushing can represent a significant volume of water lost to irrigation, particularly when clay content is very high as can be seen in parts of the Murray and Darling Rivers," he says.

"In the driest continent on earth the use of polyacrylamides represents a novel means for growers to increase water use efficiency, yet maintain farm profitability.

"The extensive research on polyacrylamides world wide, of which this is just a part, suggests that uptake of this technology could well become common practice in the not-too-distant future.

"With the reality of water restrictions facing many growers in the Murray Darling Basin, the benefits of using polyacrylamide as part of their irrigation management program should be seriously considered."

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