Lawn pH Testing: Understanding Jacksonville's Soil

You fertilize on schedule, water appropriately, mow at the right height, and yet your Jacksonville lawn still looks pale, grows slowly, or develops mysterious problems. The fertilizer you're applying should be working, but it's like your grass can't access the nutrients. The likely culprit isn't what you're doing—it's what's happening at the chemical level in your soil.

Soil pH, the measure of acidity or alkalinity, controls nutrient availability to grass roots. Even if your soil contains adequate nitrogen, phosphorus, potassium, and micronutrients, your grass can't absorb them if pH is outside the optimal range. It's like having a full pantry but a locked door—the food is there, but you can't access it.

At Jax Sod, we've spent 37+ years working with Northeast Florida soils, and we've seen countless Jacksonville homeowners struggle with nutrient deficiencies that weren't nutrient problems at all—they were pH problems. A simple soil test revealing pH out of range explains yellowing St. Augustine, slow Bermuda growth, and fertilizer that seems ineffective.

In this guide, we'll explain why pH matters, what Jacksonville's typical soil pH looks like, how to test your soil properly, and how to adjust pH for optimal grass health. Whether you're in Riverside with 100-year-old native soil or Nocatee with imported fill dirt, understanding and managing soil pH will transform your lawn care results.

Why Soil pH Matters

Soil pH is measured on a 0-14 scale, with 7 being neutral. Values below 7 are acidic, while values above 7 are alkaline (or basic). Most lawn grasses prefer slightly acidic to neutral soil, typically 6.0-7.0, though specific preferences vary by grass type.

Nutrient Availability

Different nutrients become available or locked up depending on pH. In very acidic soil (pH below 5.5), aluminum and manganese become soluble and can reach toxic levels. Iron, while abundant in Florida soils, becomes unavailable in alkaline conditions (pH above 7.5), causing the yellow color (chlorosis) Jacksonville homeowners often see.

Nitrogen, phosphorus, and potassium—the primary nutrients in fertilizer—are optimally available in the 6.0-7.0 range. As pH drops below 5.5 or rises above 7.5, these nutrients become chemically locked in forms grass roots can't absorb. You can apply all the fertilizer you want, but if pH is wrong, your grass literally can't use it.

This is why soil testing before fertilization is so critical. Applying more fertilizer to yellowing grass when the real problem is pH just wastes money and contributes to environmental runoff without solving the problem.

Microbial Activity

Beneficial soil microorganisms that decompose organic matter, fix nitrogen, and suppress disease organisms thrive in the 6.0-7.0 pH range. As pH becomes more acidic or alkaline, microbial populations decline and diversity decreases. This affects everything from nutrient cycling to disease resistance.

Jacksonville homeowners using organic fertilizers rely entirely on soil microbes to convert organic nitrogen into plant-available forms. If pH is too low or high, these microbes can't function effectively, making organic fertilizers perform poorly even when they'd work well at correct pH.

Root Health

Grass roots function best within their preferred pH range. Outside this range, root growth slows, stress tolerance decreases, and disease susceptibility increases. A St. Augustine lawn in Jacksonville maintaining 6.5 pH develops deeper, healthier roots than identical grass at 5.0 or 8.0 pH, even with identical care otherwise.

Deeper roots mean better drought tolerance, improved nutrient uptake, and stronger overall health—all critical in Jacksonville's challenging summer conditions.

Jacksonville's Typical Soil pH

Native soils throughout most of Jacksonville, Duval County, Clay County, and St. Johns County are naturally acidic, typically ranging from 5.5 to 6.5. This acidity results from our sandy soil composition, high rainfall leaching basic elements, and lack of limestone bedrock (unlike Central and South Florida, where limestone creates alkaline soils).

Geographic Variations

Coastal areas (Jacksonville Beach, Atlantic Beach, Neptune Beach, Ponte Vedra): Slightly higher pH due to salt spray and shell content in soil, typically 6.0-6.5. Some beachfront properties with high shell content can approach 7.0.

Inland Jacksonville (Riverside, Avondale, San Marco, Arlington): Classic acidic sandy soil, typically 5.5-6.0. Older neighborhoods with decades of oak leaf accumulation sometimes drop to 5.0-5.5.

Clay County (Orange Park, Fleming Island, Middleburg, Green Cove Springs): Similar to inland Jacksonville, 5.5-6.0, with some areas of heavy clay subsoil that tends slightly more acidic.

St. Johns County (Fruit Cove, Nocatee): Variable depending on development age and fill dirt sources. Established areas run 5.5-6.0, while new construction varies wildly based on imported soils.

New Construction Issues

The most dramatic pH variations occur in new developments throughout Northeast Florida. Contractors often import fill dirt from various sources—some from clay pits, some from other construction sites, some from agricultural areas that have been limed for decades. We've tested adjacent lots in Nocatee, Town Center, and new Ponte Vedra developments that varied from pH 4.5 to 8.5.

Alkaline fill dirt (pH 7.5-8.5) creates immediate and persistent problems for Jacksonville lawns. St. Augustine, Bermuda, and Zoysia all struggle in alkaline soil, developing iron chlorosis (yellowing while veins remain green), slow growth, and disease susceptibility. Correcting high pH is more difficult and expensive than correcting low pH, making soil testing critical before sodding new construction.

If you're building in a new development, test soil pH before final grading and definitely before sod installation. Correcting pH problems is vastly easier before grass is installed than after.

How to Test Your Soil pH

Jacksonville homeowners have three testing options, ranging from quick-and-dirty approximations to detailed laboratory analysis.

DIY pH Test Kits

Home Depot, Lowe's, and garden centers sell pH test kits for $10-20. These use either litmus paper or chemical indicators that change color based on pH. You mix a soil sample with distilled water, insert the test strip or add indicator drops, and compare the resulting color to a chart.

Advantages: Immediate results, inexpensive, good for quick checks or testing multiple locations.

Disadvantages: Less accurate than lab tests (typically +/- 0.5 pH units), don't provide nutrient information, user error affects results.

For Jacksonville homeowners who want a quick assessment or are testing multiple areas around their property, DIY kits provide useful information. Follow instructions carefully, use distilled water (tap water pH affects results), and test several locations for representative results.

Electronic pH Meters

Battery-powered or probe-style pH meters are available for $15-100. You insert the probe into moist soil and read pH from a dial or digital display.

Advantages: Quick, reusable, portable for testing multiple locations.

Disadvantages: Accuracy varies wildly by model, cheap meters are unreliable, requires calibration, affected by soil moisture and salt content.

We've found most inexpensive electronic meters sold at garden centers provide inconsistent results in Jacksonville's sandy soils. Professional-grade meters ($100+) are accurate but overkill for homeowner use. Save the money and use UF/IFAS testing instead.

UF/IFAS Extension Soil Testing

The University of Florida IFAS Extension offers comprehensive soil testing for Jacksonville residents through the Duval County Extension office. For $7 per sample, you get laboratory-grade analysis of pH, nutrients, and specific recommendations for correcting deficiencies.

This is by far the best value and most accurate option. Here's how to collect and submit samples:

1. Collect soil samples: Use a soil probe, trowel, or shovel to collect 10-15 subsamples from your lawn. Go 3-4 inches deep, avoiding surface thatch and grass. Mix all subsamples together in a clean bucket.

2. Fill sample bag: Place 1-2 cups of the mixed soil in a sealed plastic bag or the sample bags provided by the Extension office.

3. Complete submission form: Download the form from the UF/IFAS website or pick one up at the Extension office. Indicate you're testing lawn/turf, specify your grass type, and note any specific concerns (yellowing, slow growth, etc.).

4. Submit sample: Drop off at the Duval County Extension office (1010 N. McDuff Avenue, Jacksonville, FL 32254) or mail according to their instructions. Payment is $7 cash or check.

5. Receive results: Results typically arrive via email within 7-10 business days. You'll receive pH, nutrient levels, and specific recommendations for lime or sulfur application if needed.

Jacksonville Pro Tip: Test different areas separately if your property has variations. Front and back yards often differ. Shaded areas under oaks may be more acidic than open lawn. New construction fill sections should be tested separately from existing soil areas.

Interpreting Soil Test Results

Your UF/IFAS soil test report will include pH measurement and interpretation. Here's how to understand what those numbers mean for your Jacksonville lawn.

pH Ranges and Grass Health

| pH Range | Classification | Effect on Jacksonville Grasses | |----------|---------------|--------------------------------| | Below 4.5 | Extremely acidic | Aluminum toxicity, nutrient deficiencies, poor growth | | 4.5-5.5 | Very acidic | Limited nutrient availability, acceptable for Bahia | | 5.5-6.0 | Moderately acidic | Good for Bermuda and Bahia, acceptable for St. Augustine and Zoysia | | 6.0-7.0 | Slightly acidic to neutral | Optimal for St. Augustine, Zoysia, Bermuda | | 7.0-7.5 | Slightly alkaline | Acceptable but iron chlorosis risk increases | | Above 7.5 | Alkaline | Iron deficiency, limited nutrient availability, poor grass health |

What the Numbers Tell You

pH 5.5-6.5: Your Jacksonville lawn is in the ideal range. No pH adjustment needed. Focus on appropriate fertilization and maintenance practices.

pH 5.0-5.5: Slightly low for St. Augustine and Zoysia but acceptable for Bermuda and Bahia. Consider light lime application (25-50 lbs per 1,000 sq ft) to bring pH up slightly, though not urgent.

pH below 5.0: Definitely too acidic. Apply lime according to test recommendations, typically 50-100 lbs per 1,000 sq ft. Retest after 6 months to monitor improvement.

pH 7.0-7.5: Slightly alkaline. Monitor for iron chlorosis. If yellowing occurs, apply iron sulfate rather than adjusting pH (see below).

pH above 7.5: Too alkaline for Jacksonville grasses. Apply sulfur or acidifying fertilizers according to test recommendations. This is common in new construction and requires aggressive correction.

The UF/IFAS report will provide specific amendment rates based on your pH, soil type, and grass species. Follow these recommendations rather than generic product label instructions for best results.

Ideal pH for Each Grass Type

Different grasses tolerate different pH ranges. Knowing your specific grass type's preferences helps you target pH adjustments appropriately.

St. Augustine Grass (Floratam, Palmetto, CitraBlue, ProVista)

Ideal pH: 6.0-7.0

St. Augustine performs best in neutral to slightly acidic soil. At pH below 5.5, you'll see yellowing, slow growth, and increased disease susceptibility. St. Augustine is particularly sensitive to iron deficiency in alkaline soils—pH above 7.5 causes the characteristic yellowing with green veins (chlorosis) even when iron is present in soil.

For St. Augustine lawns in Riverside, Mandarin, or San Marco with pH in the low 5s from oak tree acidity, apply dolomitic lime to raise pH into the 6.0-6.5 range. For new construction properties with alkaline fill (pH 7.5+), apply sulfur to lower pH.

Bermuda Grass (TifTuf, Celebration, Latitude 36, Tifway 419)

Ideal pH: 5.5-7.0

Bermuda is the most pH-tolerant grass commonly used in Jacksonville. It performs acceptably in moderately acidic soil (5.5) and tolerates neutral to slightly alkaline conditions (7.0-7.5) better than other warm-season grasses.

Bermuda lawns in Jacksonville Beach, Ponte Vedra, or Nocatee with pH in the low 6s are perfectly fine with no adjustment needed. Even at 5.5 or 7.5, Bermuda will usually perform adequately, though optimal range still provides better results.

Zoysia Grass (Empire, Zeon, Icon, Palisades)

Ideal pH: 5.5-7.0

Zoysia preferences are similar to Bermuda, tolerating a fairly wide pH range. However, Zoysia is more sensitive to iron deficiency than Bermuda, so alkaline soils (pH above 7.0) cause more visible yellowing.

Zoysia lawns in new developments with alkaline fill should be treated aggressively with sulfur to lower pH. The dense growth habit and deep green color that make Zoysia attractive disappear when iron chlorosis sets in from high pH.

Bahia Grass (Argentine, Pensacola)

Ideal pH: 5.5-6.5

Bahia actually prefers slightly more acidic soil than other Jacksonville grasses and performs well in the 5.0-6.0 range that's too acidic for St. Augustine or Zoysia. This makes Bahia ideal for acidic soils in wooded areas, under oaks, or in areas where soil amendment is impractical.

Bahia lawns testing at pH 5.0-5.5 don't need lime application. Focus on appropriate fertilization and mowing instead. Only apply lime if pH drops below 5.0, where even Bahia's tolerance is exceeded.

Raising Soil pH: Lime Applications

When Jacksonville soil is too acidic (below 5.5 for most grasses), lime application raises pH by neutralizing soil acidity. Lime is ground limestone, primarily calcium carbonate, that reacts chemically with acidic soil components.

Types of Lime

Dolomitic lime: Contains both calcium carbonate and magnesium carbonate. This is the preferred choice for Jacksonville soils, which are often deficient in magnesium. Most garden centers and home improvement stores carry dolomitic lime in 40-50 lb bags.

Calcitic lime: Pure calcium carbonate without magnesium. Use only if soil testing shows excessive magnesium, which is rare in Northeast Florida.

Pelletized lime: Compressed lime pellets that spread easily through broadcast spreaders without the dust of powdered lime. More expensive but cleaner and easier to apply. Popular choice for Jacksonville homeowners.

Hydrated (slaked) lime: Fast-acting but caustic. Not recommended for lawns—too easy to burn grass. Stick with standard dolomitic or calcitic lime.

Application Rates and Timing

Your UF/IFAS soil test will specify lime application rates based on your current pH and target pH. General guidelines for Jacksonville's sandy soils:

• To raise pH 0.5 units: Apply 25-50 lbs dolomitic lime per 1,000 sq ft
• To raise pH 1.0 units: Apply 50-100 lbs dolomitic lime per 1,000 sq ft
• To raise pH 1.5+ units: Apply 100 lbs per 1,000 sq ft, wait 6 months, retest, and apply additional if needed

Never apply more than 100 lbs per 1,000 sq ft in a single application. Excessive lime creates alkaline conditions and ties up nutrients. If you need large pH increases, apply 100 lbs, wait 6 months, retest, and apply more if still needed.

Best timing for Jacksonville: Apply lime in fall (October-November) or early spring (February-March) when grass is actively growing but not stressed by heat. Lime reacts slowly—expect 3-6 months before significant pH change occurs. Fall application working through winter provides corrected pH by spring green-up.

Application Method

1. Mow grass: Mow your lawn shorter than normal to expose more soil surface.

2. Calibrate spreader: Follow lime bag instructions for your specific spreader model. Lime density varies by product.

3. Apply evenly: Use a broadcast spreader, walking in overlapping passes to ensure complete coverage. Avoid piling lime—more is not better.

4. Water in lightly: Apply 0.25 inches of irrigation to wash lime off grass blades and into soil. Heavy watering can cause runoff before lime incorporates.

5. Avoid traffic: Keep foot traffic minimal for 48 hours to avoid tracking wet lime throughout the property.

Lime isn't a quick fix. It may take 6 months to see full pH change, especially in Jacksonville's sandy soil with high rainfall leaching. Be patient and retest 6 months after application to confirm results.

Jacksonville Pro Tip: Don't lime just because your neighbor does or because you read you should lime annually. Only apply lime based on soil test results. Unnecessary lime applications create high pH problems that are harder to fix than acidic soil.

Lowering Soil pH: Sulfur and Acidifying Amendments

Alkaline soil (pH above 7.5) is increasingly common in Jacksonville new construction. Lowering pH is more difficult than raising it and requires more frequent applications.

Elemental Sulfur

The primary pH-lowering amendment is elemental sulfur (also called soil sulfur or garden sulfur). Soil bacteria convert sulfur to sulfuric acid, which neutralizes alkalinity and lowers pH.

Sulfur works slowly—even more slowly than lime. Expect 6-12 months for full pH change, as bacterial conversion is required. This makes sulfur application a long-term strategy, not a quick fix.

Application rates for Jacksonville soils:

• To lower pH 0.5 units: Apply 5-10 lbs sulfur per 1,000 sq ft
• To lower pH 1.0 units: Apply 10-20 lbs sulfur per 1,000 sq ft
• To lower pH 1.5+ units: Apply 20 lbs per 1,000 sq ft, wait 6 months, retest, and apply more if needed

Never exceed 20 lbs per 1,000 sq ft in a single application. Excessive sulfur creates extremely acidic conditions and can burn grass.

Iron Sulfate

For alkaline soils causing iron chlorosis, iron sulfate provides dual benefits: immediate iron for greening and slow pH reduction as sulfate converts to sulfuric acid. Apply at 5-10 lbs per 1,000 sq ft every 6-8 weeks during growing season.

Iron sulfate is faster-acting than elemental sulfur for correcting yellowing but provides less total pH reduction. Use iron sulfate for immediate color improvement while elemental sulfur works on long-term pH correction.

Ammonium Sulfate Fertilizer

Nitrogen fertilizers containing ammonium sulfate have acidifying effects over time. For Jacksonville lawns on alkaline soil, using ammonium sulfate (21-0-0) for routine nitrogen applications slowly reduces pH while fertilizing.

This isn't a substitute for elemental sulfur when serious pH reduction is needed, but it prevents pH from continuing to rise and provides modest acidification over seasons.

Sulfur-Coated Urea

Some slow-release fertilizers use sulfur coating, which provides acidification as the coating breaks down. Look for SCU (sulfur-coated urea) products if you're managing slightly alkaline soil and want your fertilizer to help rather than worsen the issue.

Jacksonville-Specific Soil pH Issues

Northeast Florida's unique conditions create specific pH challenges homeowners need to understand.

Alkaline Fill Dirt in New Construction

This is the most common pH problem we encounter. Developers importing fill dirt from agricultural areas that have been limed for crops, from limestone-bearing regions, or from alkaline clay pits create pH levels up to 8.5-9.0.

If you're building in new developments in Nocatee, Town Center, Durbin Crossing, or any Clay County subdivision, absolutely test pH before sodding. We've seen beautiful new TifTuf Bermuda or Palmetto St. Augustine installed over alkaline fill that yellows within 30 days despite perfect care.

Correcting pH 8.5 soil down to 6.5 requires 18-24 months of aggressive sulfur applications. Do this before sod installation, not after. If discovered after sodding, commit to regular iron sulfate applications for immediate color while elemental sulfur works long-term.

Coastal Soil Variations

Properties in Jacksonville Beach, Neptune Beach, Atlantic Beach, and Ponte Vedra near the ocean have naturally higher pH from shell content and salt spray. This is moderate (6.5-7.0) and manageable. Regular iron sulfate applications during growing season prevent chlorosis without needing to lower pH significantly.

Beachfront properties with extensive shell in soil may run 7.5-8.0. These locations benefit from Bermuda or Zoysia selection over St. Augustine, as they tolerate higher pH better. Alternatively, commit to regular acidification with sulfur and iron treatments.

Oak Trees and Acidity

Neighborhoods with mature live oaks, water oaks, and laurel oaks—common throughout Riverside, Avondale, San Marco, and Mandarin—develop more acidic soil over time as oak leaves decompose. Oak leaf litter produces organic acids that lower pH.

Shaded lawn areas under oak canopies often test 0.5-1.0 pH units lower than open lawn areas. If soil tests show pH 5.0-5.5 under oaks but 6.0 in open lawn, apply lime only to shaded areas, leaving open areas untreated. Separate applications by zone prevent over-liming open areas.

Testing Frequency and Timing

How often should Jacksonville homeowners test soil pH? The answer depends on your situation.

Initial Test

If you've never tested, do so immediately. Soil pH is foundational to lawn health. Understanding your baseline before making fertilizer and amendment decisions prevents wasted effort.

Routine Testing

Established lawns with good health: Test every 3-4 years to monitor gradual changes from fertilizer use, rainfall, and organic matter decomposition.

New construction or recent pH correction: Test annually for 2-3 years to confirm pH is moving in the right direction and stabilizing in the target range.

Problem lawns with persistent yellowing or poor growth: Test annually until the problem is resolved and lawn health stabilizes.

Best Testing Time

Late winter or early spring (February-March) is ideal for Jacksonville lawns. Test results guide your spring fertilization and amendment program. Testing in fall (September-October) also works and allows lime application before winter.

Avoid testing during extreme drought or immediately after heavy fertilization, as these can skew results.

How pH Connects to Fertilizer Effectiveness

Understanding the relationship between pH and fertilizer performance prevents common Jacksonville lawn care mistakes.

Nitrogen Efficiency

In optimal pH (6.0-7.0), nitrogen fertilizers convert efficiently to plant-available forms. In acidic soil (below 5.5), nitrogen conversion slows and some nitrogen leaches away before grass can use it. In alkaline soil (above 7.5), nitrogen availability decreases and more volatilizes as ammonia gas.

This means identical fertilizer applications at pH 5.0 and 6.5 produce dramatically different grass responses. The pH 6.5 lawn greens up beautifully while the pH 5.0 lawn barely responds. Homeowners often respond by applying more fertilizer, which doesn't solve the pH problem and contributes to environmental runoff.

Phosphorus Lockup

Phosphorus becomes highly unavailable in alkaline soil. At pH 7.5-8.0, even high-phosphorus fertilizers provide little benefit because phosphorus chemically binds with calcium in alkaline conditions, forming insoluble compounds grass roots can't absorb.

For Jacksonville new construction with alkaline fill, phosphorus fertilizers won't improve root growth until pH is corrected. Lower pH first with sulfur, then phosphorus applications become effective.

Micronutrient Management

Iron, manganese, zinc, and other micronutrients become severely limited in alkaline soil. The classic symptom—yellow grass with green veins—results from iron present in soil but chemically unavailable to grass at high pH.

Foliar iron sprays provide temporary greening without solving the root problem. Correct pH, and iron already in your soil becomes available. This is far more sustainable than repeated iron applications.

Conclusion

Soil pH is one of the most important yet most overlooked factors in Jacksonville lawn health. Jacksonville's naturally acidic sandy soils generally fall in acceptable ranges, but new construction fill dirt and specific site conditions create wide variations that dramatically affect grass performance.

A simple $7 UF/IFAS soil test reveals your pH, provides specific recommendations for corrections, and explains nutrient deficiencies that might be pH-related rather than fertilizer-related. Whether you need lime to raise pH in acidic soil or sulfur to lower pH in alkaline conditions, proper pH management makes every other aspect of lawn care more effective.

Different grass types prefer different pH ranges. St. Augustine and Zoysia perform best at 6.0-7.0, Bermuda tolerates 5.5-7.0, and Bahia accepts 5.5-6.5. Match your pH management to your specific grass type for optimal results.

Test your soil now if you haven't recently. If pH is out of range, commit to correction with appropriate amendments. Retest annually until pH stabilizes in the optimal range. The investment of time and money is minimal compared to the dramatic improvement in fertilizer effectiveness, grass health, and overall lawn appearance.

Ready to establish the healthiest possible lawn in Jacksonville? Contact Jax Sod today at (904) 901-1457 or visit jaxsod.com for expert advice on turf selection, soil preparation, and maintenance strategies that account for your specific soil conditions. With 37+ years serving Northeast Florida, we understand Jacksonville's soil challenges and can help you succeed.