Spring 2011 I had sown too many seeds to plant in the indoor grey water planters and the suspended food growing buckets. Being a plant lover I could not let the extra starts die, so I planted them in the only other place they would be able to grow out here on the High Desert Mesa, the Visitors Center black water planter. The black water planter is a contained out door botanical cell located between the septic tank and the leach field. Here, black water planters usually have cold hardy ornamentals such as red willows, cold hardy fruit trees such as winter pear and apple, and wild flowers growing, providing a habitat and food source for wild birds and small animals out here on the Mesa.
It takes years to amend the Mesa soil which is made up of volcanic ash and sticky clay, not very conducive to growing food. So it is not easy for serious self sustainable Earthship owners to make a garden outside out here, to supplement growing food all year inside the green house grey water planters.
A friend out here on at the Greater World Earthship Community had loaned me her copy of THE HUMANURE HANDBOOK by Joseph Jenkins, a book every person should read. Inspired by this book, I decided to conduct an experiment in using the black water planter as an outside garden in which to plant food. I was curious weather the vegetables would be contaminated with bacteria. An intern who was working with me at the time, (now living in the Greater World Earthship Community, ) networked and had good connections, put me in touch with the Professor of Food Safety Microbiology from the Department of Food Science and Nutrition, University of Minnesota, Dr Francisco Diez-Gonzalez. He was interested in helping us by testing the vegetables we had planted in the black water planter for bacteria.
We had planted watermelon, winter squash, hot and sweet peppers, kale, tomatoes and potatoes in the black water planter. We also sent some bananas to be tested. I suspected that root crops and leafy greens would have more chance of being contaminated, than the produce on larger plants or vines. We also sent soil samples of three different black water planters. Below are the results we received back from Dr Francisco Diez-Gonzalez.
No Escherichia coli was detected in any of the above mentioned produce. However, the kale sample had a relatively high count of coliforms, which are bacteria closely related to E. coli. The potatoes had a small amount. Some of these bacteria naturally occur in low counts in all produce. A high count of bacterial CFU/g suggests that there may be too many bacteria, which means that the chances for pathogenic bacteria could increase, as in the case of the kale sample.
So the conclusion I’d like to draw from this experiment is as follows. It seems that plants may have a capability to filter out bacteria by its roots and stem. It seems that the more plant material such as a stem and branches or long vines, or the taller the plant is, the more capability it may have to filter out bacteria. The closer the edible part of the produce is to the soil the chances for contamination increases. So no root crops or leafy greens in the black water planter.
I have eaten watermelon and bananas, obviously raw, grown in black water planters, and did not get ill in any way. I do however have a pretty strong constitution. I have also eaten the peppers, and the winter squash cooked and did also not get sick. All this produce was grown in the black water planter of a public facility, which is a risk in itself, as we do not know what the individuals who came to and used the facility, had ingested. But Earthship homeowners know what they have put into their bodies and hence what is coming out.
So if you are an Earthship owner, you can, AT YOUR OWN RISK use your black water planter as a garden to grow certain foods. I would however recommend you cook all the produce, that is heating it above 155 degrees Farenheit, at which point pathogenic bacteria are killed. Our ancestors always used to make their vegetable gardens over their leach fields.
Because the Visitors Center at the Greater World Community is a public facility, its black water planter will only be planted with plants that provide wild life with a protected habitat and flowers, to attract beneficial insects and birds.