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Urban Horticultural Production

# Soil Testing in Urban Horticulture

Urban horticulture is expanding as city residents transform vacant lots, backyards, and community gardens into spaces for fresh produce, herbs, and flowers. These gardens enhance community health, biodiversity, and sustainability. However, urban soil often faces issues from contamination, compaction, and poor management. Soil testing is a vital first step for urban growers, revealing key information about nutrients, pH, organic matter, and possible contaminants.

This guide provides a simple, step-by-step approach to soil testing, helping urban growers create healthy, productive, and safe gardens.

## Why Test Urban Soils?

## Common concerns in urban soil include:

1. pH extremes (too acidic or too alkaline)

2. Compaction and poor drainage

3. Heavy metal contamination (lead, arsenic, cadmium)

4. Excess salt from past construction or irrigation

5. Nutrient imbalances (too much or too little nitrogen, phosphorus, potassium)

## Soil testing helps you:

• Identify nutrient needs

• Determine pH adjustments

• Detect potential contamination

• Avoid unnecessary fertilizer use

• Reduce environmental harm

• Support long-term soil health

• Plan crop selection, amendments, and irrigation methods based on soil conditions

## When and How Often to Test

When to Test: Ideally, test soil 3-6 months before planting, especially if amendments are needed.

How Often: At least every 2–3 years for ongoing gardens. Test annually if growing food intensively or applying compost/fertilizer regularly.

## How to Collect a Soil Sample

## Tools Needed

• Pair of gloves

• Clean plastic bucket

• Clean spade or shovel

• Clean travel or soil probe

• Ziplock bag or soil sample box (provided by testing lab)

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## Depth of Sample


<table border=1 style='margin: auto; word-wrap: break-word;'><tr><td style='text-align: center; word-wrap: break-word;'>Lawn</td><td style='text-align: center; word-wrap: break-word;'>3-4 Inches</td></tr><tr><td style='text-align: center; word-wrap: break-word;'>Flower Garden</td><td style='text-align: center; word-wrap: break-word;'>4-6 Inches</td></tr><tr><td style='text-align: center; word-wrap: break-word;'>Shrub Beds</td><td style='text-align: center; word-wrap: break-word;'>6-8 Inches</td></tr><tr><td style='text-align: center; word-wrap: break-word;'>Vegetable Gardens</td><td style='text-align: center; word-wrap: break-word;'>4-6 Inches</td></tr><tr><td style='text-align: center; word-wrap: break-word;'>Trees</td><td style='text-align: center; word-wrap: break-word;'>4-8 Inches</td></tr><tr><td style='text-align: center; word-wrap: break-word;'>Pastures</td><td style='text-align: center; word-wrap: break-word;'>4-6 Inches</td></tr></table>

## Sampling Locations

Look for different environments in your field or garden and collect separate samples from areas that are mostly sunny versus those in deep shade, or dry areas versus wet areas.*Do not sample compost areas, under the dripline of trees, or near sidewalks and driveways.

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## Recommended

Recommended

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## Collecting Your Sample

• Clear away mulch and surface debris.

- Dig 6-8 inches deep in garden beds (or 3–4 inches for lawns).

• Take 10–15 subsamples from different spots across the area.

• Mix subsamples thoroughly in the bucket.

- Fill the sample bag with about 2 cups of mixed soil.

- Label your sample with the area’s name (e.g., “Backyard Bed” or “Front Planter”).

1 Remove debris

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2 Collect soil cores

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3 Combine samples

4 Prepare sample

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## Soil Testing Resources in Louisville

KSU West Louisville Extension Office

1300 Muhammad Ali Blvd, Louisville, KY 40203

Dr. Alhagie K. Cham

alhagie.cham@kysu.edu

Jefferson Co. Soil & Water Conservation District

4229 Bardstown Rd Ste. 203, Louisville, KY 40218

Dave Nichter

soiltech@jeffcd.org

KSU Soil Lab

Dr. Mahateme Gebremedhin

maheteme.gebremedhin@kysu.edu

Jacob Brown, MSc

jacob.brown1@kysu.edu

## For more information, contact:

#### Dr. Alhagie K. Cham

Senior Extension Associate,

Urban Horticulture Production

(502) 597-6570

 alhagie.cham@kysu.edu

1300 Muhammad Ali Blvd., Louisville, KY 4020

## Contributors

Dr. Maheteme Gebremedhin

Assistant Professor, Soil

Science

Jacob Brown

Research Assistant

Kelly Rawalt

Food Systems Coordinator

Dave Nichter

Soil & Water Conservation

Technician

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## Sources

Allen, T., Kariuki, S., Mangan, F., Parkash, O., Xing, B., & Barros, Z. (2015). How and why to measure soil contaminants in urban settings (Ref. No. SPTTL_12).  https://www.umass.edu/agriculture-food-environment/soil-plant-nutrient-testing-laboratory/fact-sheets/how-why-to-measure-soil-contaminants-in-urban-settings.

Craul, P. J. (1985). A description of urban soils and their desired characteristics. Arboriculture & Urban Forestry, 11(11), 330–339. https://doi.org/10.48044/jauf.1985.071.

Wu, Q., & Congreves, K. A. (2024). Soil health benefits associated with urban horticulture. Science of The Total Environment, 912, 168852. https://doi.org/10.1016/j.scitotenv.2023.168852.