Know Your Soil
Healthy gardens start below the surface. A simple soil test tells you exactly what your soil needs so you can grow stronger plants with less guesswork.
Why Test Your Soil?
Most gardening problems start with the soil. Testing takes the guesswork out of fertilizing and amending.
Stop Guessing
Know exactly which nutrients your soil has and which it lacks. No more over-fertilizing or under-fertilizing.
Save Money
Apply only the amendments your soil actually needs. A $10 test can save you hundreds in wasted fertilizer.
Healthier Plants
Balanced soil grows stronger, more disease-resistant plants that need less intervention from you.
Common NE Florida Soil Issues
• Sandy soil: Drains too fast, low in organic matter and nutrients
• High pH: Coastal areas often have alkaline soil from shell deposits, locking out iron and manganese
• Low organic matter: Florida sand has very little humus, leading to poor water and nutrient retention
• Nematode pressure: Sandy soil harbors root-knot nematodes that damage vegetable roots
How to Collect a Soil Sample
Follow these steps for accurate results. The whole process takes about 15 minutes.
Gather Your Tools
You need a clean trowel or spade, a clean plastic bucket, and a quart-sized plastic bag. Avoid using galvanized or brass tools, which can contaminate the sample.
Take Multiple Sub-Samples
Dig 6 inches deep in 8-10 random spots across the area you want tested. Remove surface debris first. Put each sub-sample in your bucket.
Mix and Bag
Thoroughly mix all sub-samples together in the bucket. Scoop about 2 cups of the mixed soil into your plastic bag. Label the bag with the area name (e.g., "Front Lawn" or "Veggie Garden").
Let It Dry
Spread the soil on newspaper and let it air-dry for 24 hours. Do not oven-dry or microwave it. Wet soil can lead to inaccurate results.
Submit to a Lab
Drop your sample off at the UF/IFAS St. Johns County Extension Office, or mail it to the UF Soil Testing Lab. Results typically arrive in 5-7 business days.
Pro tip: Test different areas separately. Your lawn, vegetable garden, and flower beds may have very different soil profiles.
What Your Results Mean
Your soil test report will include pH, macronutrients, and micronutrients. Here is how to read the key numbers.
Soil pH
pH measures how acidic or alkaline your soil is on a scale of 0-14. Most plants prefer slightly acidic soil (6.0-6.5). Northeast Florida soils typically range from 5.5 to 8.0 depending on location.
Too Acidic
Add lime to raise pH. Common in older, inland landscapes.
Ideal Range
Most nutrients are available to plants. No major adjustments needed.
Alkaline
Add sulfur or organic matter. Common near the coast due to shell content.
Key Nutrients (N-P-K)
Nitrogen (N)
Drives leafy green growth. Low nitrogen means pale, slow-growing plants.
Fix low N: Compost, blood meal, or a balanced fertilizer.
Phosphorus (P)
Supports root development and flowering. Florida soils are often adequate or high.
Fix low P: Bone meal or rock phosphate. Do not add if levels are already adequate.
Potassium (K)
Strengthens plant cell walls and disease resistance. Sandy soils often run low.
Fix low K: Wood ash, greensand, or potassium sulfate.
Micronutrients to Watch
Iron (Fe): Deficiency causes yellow leaves with green veins. Common in high-pH soils.
Manganese (Mn): Similar symptoms to iron deficiency. Often locked out above pH 7.0.
Magnesium (Mg): Older leaves yellow first. Apply Epsom salts if low.
Calcium (Ca): Causes blossom-end rot in tomatoes. Usually adequate near the coast.
Local Soil Testing Resources
Northeast Florida gardeners have access to affordable, reliable soil testing through the University of Florida.
UF/IFAS Soil Testing Lab
The University of Florida operates a comprehensive soil testing lab that provides detailed analysis and specific recommendations for Florida soils.
- ✓ Standard test: ~$7 per sample
- ✓ Results in 5-7 business days
- ✓ Includes fertilizer recommendations
- ✓ Florida-specific guidance
St. Johns County Extension
Your local extension office can help you interpret results, provide gardening advice, and answer questions about soil health in our area.
- ✓ Free consultations with agents
- ✓ Drop-off location for soil samples
- ✓ Master Gardener help desk
- ✓ Local gardening workshops
3125 Agricultural Center Drive, St. Augustine, FL 32092
When to test: Test your soil every 2-3 years, or any time you notice unexplained plant problems. The best time is late fall or early spring before you start planting.
Need Help Reading Your Soil Test?
Bring your results to Southern Horticulture. Our team can help you pick the right amendments and plants for your specific soil conditions.