AU: Food producers experiment with new ways to grow crops on barren opal fields

A lush green oasis lies among mine shafts on the opal fields of Lightning Ridge. Everything from avocados and olives to almonds and corn grow against a backdrop of white opal dust, as a few intrepid farmers find new ways to grow food in the outback. Ashley Steed's aquaponics greenhouse sits just off a non-gazetted dirt road in one of the outback town's many opal fields.

"There are beds made up with gravel, which holds the seedlings, and there's water flowing through those beds constantly carrying oxygen and nutrients," he said. "And the water comes from the fish tanks."

A series of large water tanks hold hundreds of silver perch — a freshwater fish that copes with both the extreme heat and winter frosts endured through the year. The fish wastewater is then pumped into a filtration system where it is re-oxygenated before it snakes through garden beds filled with gravel.

There's no soil in this system, so the gravel acts as a support structure for the plants as they grow while the constant stream of nutrient-dense water acts as the fertilizer. "There are two different bacteria, there's one that changes the ammonia that comes from the fish into a nitrite and then there are another bacteria that gets going after that and turns it into a nitrate," said Mr. Steed.

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