Saturday, October 29, 2011

Aquaponics

Published in the Sun October 30, 2011

Sometime around 1880, a Walburg farmer hand-dug a cistern to collect rainwater off his roof.  The cistern is big, about eight feet across and thirty feet deep, and completely lined with large stones.  It was built to last, and it has, for 130 years, but it is no longer used to collect rainwater.  If that farmer were to visit today he would be astonished to see what Bob and Janine Hall are doing with his cistern.

It starts with the Halls washing machine.  With several kids at home they run about twelve loads of laundry a week.  The graywater from the washing machine runs directly into the cistern.  There is a five foot opening covered with wire mesh at the top of the cistern, so you can easily look down and see the water, which looks very clean.  (Janine uses Seventh Generation laundry detergent, which is phosphate free.)  From the cistern the water is pumped into three 330 gallon tanks.  The tanks provide water for two raised gardening beds about the size and shape of pool tables.  But there is no soil in these beds; they are filled with river rock and crushed granite.  The first bed is crowded with lush, dark green tomato plants.  The other bed is newly planted with strawberries.

Both beds are equipped with an ingenious drain that allows them to automatically fill with water and then drain completely every two hours.  The surface of the gravel stays dry in the sunshine so that algae will not grow.  The tomato bed drains into a plastic pond stocked with forty small goldfish and some aquatic plants.  The pond water, which contains waste from the goldfish (and goldfish are prolific with waste) drains back into the cistern.

The ammonia waste from the fish provides nitrogen and other nutrients for the plants.  The plants, by consuming the nutrients as fertilizer, clean the water for the fish.  This symbiotic relationship between gardening and fish is called aquaponics.  The word aquaponics is a combination of the words “aquaculture”, which means fish-farming, and “hydroponics”, which means raising vegetables in nutrient-rich water.  As long as the fish and the plants are in balance, the water can be recycled through the process indefinitely.  Contrary to what you might think, aquaponics uses only 10% of the water that a dirt garden would consume.  Bob has used only washing machine water to keep his cistern filled all summer.  In fact, not only does the cistern provide water for the aquaponics system, but also for six baby fruit trees, three dogs, five goats, four sheep, three horses, and a flock of chickens.

Actually, the system just described was only Bob’s starter project.  Now he has built a large greenhouse holding five larger planting beds flourishing with peppers, lettuce, and broccoli.  There is also a hydroponic “raft” in which plants are suspended in the water without the stones.  Bob lifts up a lettuce to demonstrate the bare roots extending 12 inches into the water.  We follow the PVC pipe to a separate room at the end of the greenhouse housing a 550 gallon tank of tilapia.  The tilapia are more sensitive than goldfish, but can be harvested and eaten when they get big enough.  The tilapia reproduce in the tank.  The mother carries the eggs in her mouth until they hatch, and even after hatching she will protect hundreds of babies in her mouth until they can manage on their own.  A good aquaponics farmer can end up with a continuous supply of delicious and mercury-free fish for supper.

At one point the Halls had the tilapia outside in the goldfish pond, but unfortunately there were tragic consequences.  One night Janine noticed some movement around the pond.  Going closer with a light, she noticed a 5 foot water moccasin slithering out of the pond after a tasty snack.  Shining her light down into the cistern she saw more huge moccasins.  I wish I could have seen with my own eyes what happened next.  Bob fetched his shotgun and started blasting away into the cistern.  After the massacre they fished eight dead snakes out of the water.  But it was too late; most of their tilapia were gone.

Eventually Bob and Janine plan to sell produce from their aquaponic greenhouses, as well as provide themselves with all the fresh vegetables they can eat.  Bob says he can get 8-10 times the produce in half the time out of his aquaponic beds that he could get from his old dirt garden.  He can farm year round, and with aquaponics he doesn’t need pesticides or chemical fertilizers.  Plus there are no weeds to pull.

The Hall’s former dirt garden lies drought parched and abandoned beside the barn.  A chicken, searching for a bug she might have missed, scratches in the dust.

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