garndening aust text.

Presenter: Colin Campbell [30/04/2004]
At a disused mine site at Drake in NSW, trials are being carried out on a material that is a carefully modified residue from alumina refineries called red mud. This caustic material is turned into an inert product called Bauxol. The first application of this product was to treat contaminated acid mine water to convert it to drinking water standards or better. From this process there remained a dried reddish sediment consisting of a mixture of minerals. The next logical step was to experimentally add it to the soil. Some of the natural minerals that make up Bauxol are ingredients in antacid products for stomach complaints. When Bauxol is added to the soil it neutralises it. Because plants will absorb heavy metals and minerals that are present in the soil in which they are grown, the aim of the experiment was to see if the vegetables grown in the modified soil would show this. Because it was known that the heavy metals had been removed from water, the experiment was to see if they could be removed from the soil. Vegetables are consistently analysed to make sure that they are safe for human consumption. An honours project by a student showed that the vegetables complied with the limits that allowed them to be safely eaten. It was clear that the contamination was somehow being bound up in the soil and was not being transferred to the vegetables.

The ground at the mine site consists of mine tailings and is contaminated with heavy metals and has a pH of 2.5, which is like trying to grow plants in sulphuric acid. The experimental vegetable patch shows the benefits of what would otherwise be a waste material. Minimal germination of seed occurs with 1% of Bauxol added to the soil, however with 2% added, many more seeds germinated and all the silver beet plants were very healthy. With 5% added to the soil there is a significant improvement. A greater variety of seeds have germinated including tomatoes and pumpkin with fully developed vegetables ready to be harvested. Home gardeners would not need to add 5% because the soil that they are growing their vegetables in is already in good condition, so a maximum of 1% would be adequate.

Estelle Webber is a 17 year old student who has won several science awards, the most recent being the International Young Scientist of the Year for her work with the modified red mud. She initially set up a pot trial experiment, where different percentages of Bauxol were added to individual foam boxes of soil. Two controls were established to compare the results. To represent a broad range of species Estelle used a variety of different plants including leaf, grain and root crops. In her second trial she used a much larger area of ground and added MBO (monosulphide black ooze) to intensify the acidity of the soil, and she recorded the results over two successive seasons. Corn was used as a grain crop. The number of cobs that were harvest from each plot were recorded and the trial was very successful in showing that grown in soil with Bauxol added gave a much higher yield. The results showed that Bauxol raised the pH of the soil and bound up the toxic trace elements to make the nutrients in the soil more available to the plants, even when there is not an extreme acid sulphate soil problem. Bauxol does not neutralise acidic soil as well as lime, but it remains in the soil to continue being active as long as necessary and does not leach away. This unique product is being used all around the world to clean up polluted waterways and soils; and the result is a much healthier environment. Its potential for garden use has yet to be realised, but it may well be the soil additive of the future.

Bauxol is not available yet as a garden product. Visit the website: www.virotec.com