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Understanding Urban Soils.

Published onJul 10, 2019
Understanding Urban Soils.
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How do we determine different soils types and their functions?

“Next May, the yellowwood flowered early and profusely. Thousands of fragrant white blooms hung in long clusters; petals covered bricks, blew across grass. How beautiful, people said. How sad, though. Several years’ bud scars bunched up against each twig’s growing tip. Abundant flowers signaled a dying, and seeds found no purchase in the plaza. People admired the tree and walked on; they had lost the language that gives tongue to its tale. Once a yellowwood stood. No more. And few knew why.

Anne Spirn, Language of Landscape

In this Exploration, we will begin to understand the diverse functions and roles of soils—the foundation of all terrestrial ecosystems—and the types of life they support. We will learn to categorize various soils and the species contained therein, and begin to unravel how urban environments shape soil structure and function.

Setting Up.

Workshop Musings:

What are the different kinds of soils that exist in our neighborhood? What are they made of, and what roles do they play in our environment? What does it mean for the environment if the soil is mostly sand? mostly clay? mostly silt? How might the soil impact (or be impacted) by the surrounding environment? What does the composition of a soil tell us about the type of life it can support? How do urban soils differ from other types of soil?

Materials + Preparation:

  • Field journal with zine holder (one per participant)

  • Viewfinder (one per participant)

  • Pens and pencils

  • Tape

  • Printed, cut, and folded Feeling zines (see below)

  • Hand shovels (we used these ones)

  • Clear glass jars (we used these ones)

  • 9 - 12 soil samples from around your city or neighborhood (from, for example, your backyard, local gardens and parks, construction site, from around your library, or from your friends!)

  • Easel pad paper

  • OPTIONAL: Example soil components - loose sand, silt, and clay (email us — we will send some to you!)

  • OPTIONAL: camera and mobile printer (we used the Polaroid Zip Instant Photoprinter)

Introductory ‘Zine:

The Feeling zine introduces the diverse functions of soil, and why they are critical for ecosystem health. In addition, it provides an outline of determining what a given soil sample is composed of (and how these different compositions permit different types of life). Download and print your copies here:

(Visit this website to learn how to cut and fold the zine after printing.)

Getting Started.

Preparing the Soil Show and Tell.

The introductory activities will require some set-up in advance of participants’ arrival. First, on large sheets of easel pad paper (each group of 2-3 will work on triangle together), draw a simplified version of the soil triangle—a tool used to determine the percent composition of sand, silt, and clay in a given soil sample:

<p>Soil Show and Tell setup.</p>

Soil Show and Tell setup.

You will also have to gather soil samples prior to the start of the session (see materials list above). We suggest exploring public pathways, community and public gardens, and construction sites—ensure to gather diverse soil types to make the ‘show and tell’ more exciting!

(High-resolution USDA soil triangle available here.)

<p>Example soil characterization using the (more complex) USDA’s Soil Texture Triangle. For older explorers, it’s useful to have this version printed in case they are interested in a more comprehensive quantitative analysis of their soil samples. </p>

Example soil characterization using the (more complex) USDA’s Soil Texture Triangle. For older explorers, it’s useful to have this version printed in case they are interested in a more comprehensive quantitative analysis of their soil samples.

Running a Soil Shake.

A soil shake test can show you the different elements that make up a soil. After separation of the soil components, you can also cross-reference the relative composition of a given soil sample with your soil triangle ‘predictions.’

How to run a soil shake test:

  1. Collect some soil into a jar and fill the jar with water (fill the jar about 1/3 with soil, and top off with water).

  2. Give the jar a good shake for about 30 seconds.

  3. Let the jar sit, undisturbed, for up to 48 hours (though you will see stratification much quicker than that, in only a few minutes!).

  4. After about one hour, notice the soil separate into 3 distinct layers—the bottom layer is sand, the middle layer is silt, and the top layer is clay.

  5. Calculate the % of each layer in the soil, and use the soil triangle to determine what kind of soil it is.

<p>Reading a soil jar (from the ‘Feeling’ ‘zine)</p>

Reading a soil jar (from the ‘Feeling’ ‘zine)

Soil Show and Tell:

Field Exercise.

Soil Portraits:

This week’s field exercise is relatively simple: You’ll need jars (around 3 - 4 for each small group), shovels, collection bins, a camera (a phone is OK!), and the field journal. The goal of the exercise is to collect diverse soil samples from within one (or multiple) sites, as well as somehow document the type of life that soil supports. For example, if you find a street-adjacent compacted soil sample, dig a few inches down to collect the soil itself, but also collect a spontaneous urban species growing in it. If there is nothing growing in a soil sample, make a note of that in the field journal (this condition is equally telling of the health of that soil sample). If the species is too large to collect (for example, a tree), take an image of the life form fostered by the soil, or utilize another form of method developed in the previous field exercise (a bark rubbing; a drawing).

<p>Clumping soil can give you insight to its composition and function. </p>

Clumping soil can give you insight to its composition and function.

While you have may only 3 - 4 jars for specimen collection, take inventory of as many soil types as possible in your field journal. Do some on-site analysis in the field: clump the soil together in your hands; predict how well or not it might retain water; predict its relative composition of clay, silt, and sand; try to imagine how this sample of soil is changing over time—what is its future or past?

Coming Together

A Living Exhibition:

For the come-together discussion, patrons will share their collected soil samples, as well as the types of species respective soil types fostered. Before the discussion, though, begin by adding water to each of the collected soil samples, and perform a soil shake all together (this way the soil can start to form layers by the time the discussion component ends). Discuss:

  • Which types of soil (compositionally) supported what type of plants?

  • Did any soil samples cultivate no life forms at all?

  • What are the underlying causes of this?

  • Which soil enabled the most diverse array of plant species to grow?

  • Can any trends be noticed in associating the soil composition with the life growing within it?

<p>In our playtest with Somerville Public Library, we shared out portraits roundtable-style. </p>

In our playtest with Somerville Public Library, we shared out portraits roundtable-style.

<p>We also performed soil shakes with all of the samples collected during the field exercise.</p>

We also performed soil shakes with all of the samples collected during the field exercise.

Facilitation Tips and Additional Resources.

Example Schedule:

This is the example schedule from a playtest we ran with a local library:

Time: 2 hours

5 minutes: patrons look through the Feeling zine; discuss amongst themselves any questions or observations they might have.

10 minutes: interactive discussion on the functions of soils and why they are important (and how they differ in urban contexts); learn to categorize soils using the triangle by doing an example all together (touch test and a rubbing)

20 minutes: working in pairs, participants categorize 5-6 soil samples by feeling and placing them on the soil triangle; come-together for a discussion about what was place where and why; following the discussion, participants add water to their soil jars, shake, and let them settle while we take to the field

50 minutes: participants visit two field sites, differing in the type of vegetation they have (we chose a basketball court next to a construction site and a landscaped courtyard), collecting a soil sample as well as a plant specimen (or the image of the plant if not possible to collect) at each

20 minutes: Show-and-tell and wrap-up discussion (outside!)

10 minutes: Clean-up and hand-washing!

Takeaways:

  • Learning through feeling, and seeing of different soils.

  • Collecting sample soils from various areas of your neighborhood

  • Wondering about how location impacts soil makeup and vice versa.

Carole King - I Feel the Earth Move (Audio)

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