Water savings and hydroponic lettuce

At a time of water restrictions across metropolitan Melbourne and Victoria's farmers crying out for rain, RMIT University researchers are coming up with a bright idea to save water.

Wilson Lennard, a PhD student from RMIT's Department of Biotechnology and Environmental Biology, has found that growing Australian Murray Cod with hydroponic lettuce production can purify water by reducing the amount of waste nutrients, such as nitrate, by up to 90 per cent.

"Findings in the research project show that an integrated aquaponics strategy involving the growth of Murray Cod with hydroponic lettuce can save water," RMIT senior lecturer in ecology and aquaculture and Mr Lennard's research supervisor, Brian Leonard said.

"This approach is more effective than operating separate industries and can make efficient use of waste nutrients from the fish culture.

"Integration can add to farm diversification and provide a profit from what would otherwise be disposable waste."

"The research also found hydroponic lettuce can be grown to commercial size in three weeks, which is just as efficient as commercial hydroponics," Mr Leonard said.

Mr Leonard said that based on the findings, it is feasible to produce yields of greenhouse lettuce comparable with commercial hydroponics and also fish comparable with a commercial fish operation without additions of hydroponic nutrients to the fish wastes. However, the size of the hydroponic operation needed to be very large compared with the fish operation.

Mr Lennard's research was conducted at the aquaculture centre of RMIT University's Bundoora Campus. He received funding from the Rural Industry Research and Development Corporation and is expected to complete the research in 2005.