Tuesday, August 11, 2009

Urban Farming's Dirty Little Secret

If you have any construction or gardening experience in Brooklyn, you have encountered the two main ingredients in our soil: large rocks, and construction debris. It is difficult to believe that Brooklyn and Queens were the two counties with the largest density of agricultural land in the late 1800’s. Equally present in the soil are heavy metals due to Brooklyn’s industrial use in the 20th century.

So what to do about our dirty little secret: our soil sucks for growing edibles?

I have become plagued with questions about what makes a more sustainable urban agriculture system: soil or hydroponics, or aquaponics, or a combination?

Most people would assume less-technology-equals-more-sustainable. There is a lot of complexity to this issue, so I am going to use this blog as my research diary. Let's assume that technology scares you and that you have 'soil' to use as your growing medium. You should become intimate with your soil's qualities through testing. Start with this NY Times article that discusses safe lead levels, and then take a closer look at your soil content.

Assuming you have bric-a-brac and lead in your soil, the most sustainable method would take several years to get edibles from the plot. It would require digging several feet deep; removing large debris and rocks; mixing in organic matter (newspaper, compost, manure, etc); and planting a crop that would draw lead out of the soil. Then it gets tricky. You now have organic matter that you need to dispose of as hazardous waste: you cannot simply put it curbside and let the trash man take it away. And don't even think about composting it and putting it back in your future edible garden!

One to three years later, your soil is ready for growing edibles. Pat yourself on the back for helping to reclaim some topsoil which we are in danger of depleting due to monocultural agricultural practices, feedlots, and more.

Environmental Impact Questions: How did you dig and till your soil (manual or power)? Where did you get your compost? If bought, did it come in a plastic bag? If bought, how was it processed? If bought, where did it come from and what were the transportation costs? Same questions for any other soil amendments.

Let's assume you have a large area that would be very time-consuming to dig up or you want to start growing edibles right away. You can build raised planting beds.

Environmental Impact Questions: Where did your top soil come from and how far did it travel by truck? What's in this new soil and how was it processed? Have you helped to deplete top soil in another location? What material did you use to build your raised beds (wood, cement block, etc)? Where did it come from? How was it processed into its current form? Is it a renewable material? How long until you have to replace it?

Lots of questions. Stay tuned as I expose more dirty secrets.