Last update the trials looked something like this:
To recap: Lettuce was started inside under a grow light. Thirty of those “starts” were planted in the rooftop mixes at the FarmingUp trial site pictured above. Five of the starts were planted in the field at the Stone Barns Center, below.
At Stone Barns, Zach Wolf manages soil fertility masterfully, using practices that conform to organic standards and then some. Planting five of the FarmingUp lettuce starts in the Stone Barns field allows us to directly compare foods grown in our rooftop mixes to those coming from a well-managed field. It will help anwer the question, “Can farmers’ market quality produce be grown in engineered soils in the urban environment?”
Not long after the last update the lettuce was ready for harvest. All of the heads were gathered from both the rooftop and the Stone Barns field. We also snagged a couple heads from the corner bodega to examine what else is available locally. Tucked into a cooler, the lettuce was whisked up to Ithaca, NY where Ray Glahn awaited in his USDA lab.
(The drive up was great).
Ray showed me around his lab and then let me loose to prep samples for processing. In a great and unexpected twist, Ray suggested that each head be cut in half so that it could be processed both washed and unwashed. The difference in the amount of heavy metals found on washed and unwashed samples should indicate crud that settled onto the plants from the air. (Air quality is a perennial concern among urban food growers and the trial site is directly across the street from a cement factory). The comparison of washed and unwashed lettuce will shed light on some of the broader health implications of urban growing, at least in that section of the Gowanus, and is a layer of information that we hadn’t dreamed of collecting.
When looking for metals in trace quantities, the tiniest bit can skew results. Accordingly, in a USDA lab one doesn’t simply rinse lettuce, one rinses it in “18 mega-ohm” water. (I’m going to assume that’s really, really clean water). The air coming into the lab is well filtered and even electrical sockets, when not in use, are wrapped in plastic to ensure that rogue traces of metal don’t get any wise ideas.
Prepped heads went into a freezer where they are on hold until they can be freeze-dried, pulverized and analyzed. Many share the equipment that tests for metals and phytonutrients. We’re in the queue and will hopefully have data soon.
Figuring out what ‘nutrition’ is, is trickier than you’d think. There are so many compounds to consider that making blanket statements about nutrition becomes impossible. What if one sample is high in iron while another is high in zinc and a third is high in calcium? Those are only three out of dozens of metals and metals are only one of many classes of nutrients. For the purpose of measuring ‘nutrition’ in lettuce, we’re looking at about two dozen metals. Lettuce is also particularly high in the A vitamins – important antioxidants – so hopefully we’ll get data on some of those as well. Anecdotally, the lettuce that came off the roof looked great next to what came from the field.
Field-grown at left, straight Rooflite on the right.
Below: Lettuce grown in straight Rooflite on the right, next to lettuce grown in half Rooflite, half biocharchar/compost on left.
Hopefully we’ll have all sorts of good news to report shortly.
Thanks again Ray. Thanks too, to Rebecca Givan for putting me up in Ithaca.