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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.

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)

Why Test Urban Soils?

Common concerns in urban soil include:

pH extremes (too acidic or too alkaline)

Compaction and poor drainage

Heavy metal contamination (lead, arsenic, cadmium)

Excess salt from past construction or irrigation

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.

Depth of Sample

Lawn	3-4 Inches
Flower Garden	4-6 Inches
Shrub Beds	6-8 Inches
Vegetable Gardens	4-6 Inches
Trees	4-8 Inches
Pastures	4-6 Inches

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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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”).

2 Collect soil cores

4 Prepare sample

3 Combine samples

Sources

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

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.