Safe Soil in the City

Posted on: January 11, 2017
Portland landscape designer Carol Lindsay

Daizzie and I in my edibles garden

Safe soil in the city – smart and healthy practices for urban gardens

I love having a vegetable garden. It’s healthy, right? I love eating kale and I grow a lot of greens for smoothies year-round.  There are a few concerns about growing food in urban areas. Two concerns that apply to us all, city and suburban, are lead paint and lead exhaust from the past in our soils. Let’s be practical not scary about this.

Is my food safe to eat? What are the most important practices I can do and how can I keep it simple?  My garden is below Highway 30.  It’s an old heavily traveled highway so our soil has years of exposure to lead exhaust.

There’s no way I’d grow my food in the ground here.

My current garden practices

I’ve been assuming my food is safe to eat because:

Our community garden has raised beds with new clean soil from just three years ago.
I apply lots of compost at least three times a year.

Carol's winter kale

My garden supplies me with year round greens like kale.

I use an organic fertilizer. (OK it’s boxed Dr. Earth, not a truckload from Natures Needs because it’s very convenient and my garden is small.)  I don’t know what my NPK ratio is which makes me a bit of a lazy gardener but the food I like to grow does fine.  NPK being Nitrogen, Potassium, Phosphorous.  And yes I was trained as an advanced master gardener and yes that was a very long time ago………they teach you all about soil in the master gardener program.

I wash my produce, no nibbling right out of the garden bed. (OK once in a while a strawberry or tomato).

According to some experts I’m doing OK but I could do a lot better.

My improvements

  1. Soil areas next to old garages often have higher lead levels.

    Soil areas next to old garages often have higher lead levels.

    Reducing exposure to dust is the most effective thing you can do to reduce lead hazard in your landscape. It is typically in the first few inches of soil. This is the most important thing in the blog.  Mulch and compost applications cover your soil and protect it from dust with contaminants in it.    We want to keep the dust and soil off human skin and out of the mouth.  This is critical for babies and small children and good for the rest of us too.  Adding compost has many benefits for improving conditions for plants.  Adding compost at least twice a year can only benefit, there are no drawbacks.

  1. Here at my community garden, we could have put a barrier between our new soil and the existing ground soil. I can still do this once my winter Kale are done in March. I’ll have to get a tarp and dig out a lot of my soil so I’m going to install a metal grid and landscape fabric.  The grid is to keep the moles and gophers out of my raised bed. They may have brought some of the lead contaminated soil up into my new clean soil, and they caused a lot of havoc with the roots of my plants.  Some died or did not produce well because of the soil disturbance.
  1. I could improve the efficacy of washing my veggies by using a 1 percent vinegar solution instead of only using water. I’m thinking a large spray bottle under the sink could be used for my final wash. It’s got to be simple or I won’t do it.

Beyond these good soil management practices, I will need to do a Nutrient Analysis soil test to know what I need to add to my raised beds to improve the health and productivity of my vegetables and bind up any lead and keep it locked into my soil where it won’t cause problems for me.

Portland landscape designer in edibles garden

My garden is below Highway 30. It’s an old heavily traveled highway so our soil has years of exposure to lead exhaust.

Lead Soil Test

My client Katy had an older home in SE Portland.  I suggested a lead soil test.  She collected the soil and submitted samples for a lead test. She discovered the area where we wanted the kids play structure to go had high lead.  It was next to the neighbors’ garage.  Several inches of contaminated soil were removed.  She brought in new soil and playground chips and now has a safe play area for her toddlers.

What’s one new thing you could do this year to improve your landscape or edibles garden?  Get your soil tested.  I’m planning to collect soil from my vegetable garden and submit it to a lab for testing.  I’ll share that experience with you in another blog.