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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.
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.