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Soil pH Complete Guide: Testing, Adjusting & Maintaining
Complete soil pH guide: how to test, raise, or lower soil pH for vegetables, blueberries, lawns & flowers. Fertilizer tips for pH management.
What Is It ?
Soil pH is the single most overlooked factor in gardening success. You can apply the perfect fertilizer in the perfect amount at the perfect time, and your plants will still struggle if the soil pH is wrong. pH measures how acidic or alkaline your soil is on a scale from 0 to 14, with 7.0 being neutral. Most garden vegetables, flowers, and lawn grasses thrive in slightly acidic soil between 6.0 and 7.0, where nutrients are most available for root uptake. When pH drops below 6.0, nutrients like phosphorus, calcium, and magnesium become chemically locked in the soil — present but unavailable to plant roots no matter how much fertilizer you apply. When pH climbs above 7.5, iron, manganese, and zinc become inaccessible, causing yellowing leaves and poor growth even in nutrient-rich soil. Some plants evolved to prefer strongly acidic conditions: blueberries thrive at 4.5-5.5, and evergreens generally prefer 5.0-6.0. Understanding which fertilizers shift pH in which direction is a powerful tool — Wicked Growth Ammonium Sulfate (21-0-0) lowers pH while feeding nitrogen, and calcium-rich Wicked Organics Bone Meal (3-15-0) gently raises pH while feeding phosphorus. This guide covers how to test your soil pH accurately, how to interpret results, and how to use Old Cobblers Farm fertilizers strategically to manage pH while feeding your plants at the same time.
Why Soil pH Matters More Than Most Gardeners Realize
Think of soil pH as a gatekeeper that controls which nutrients can pass from the soil into your plant roots. At pH 6.5, virtually every essential nutrient is available in optimal amounts. Shift that pH to 5.0 or 8.0, and certain nutrients become chemically bound to soil particles in forms that roots cannot absorb. This is why you can dump fertilizer on a garden with the wrong pH and see almost no results — the nutrients are there, but the plants cannot access them. Correcting pH before adding fertilizer can be the single most cost-effective improvement you make in your garden.
Nitrogen availability is relatively stable across a wide pH range, which is why nitrogen deficiency symptoms are less commonly linked to pH problems. Phosphorus, however, is extremely pH-sensitive: it is most available between 6.0 and 7.0, and becomes increasingly locked up in both acidic and alkaline soils. In acidic soil below 5.5, phosphorus binds with iron and aluminum. In alkaline soil above 7.5, it binds with calcium. Either way, your plants starve for phosphorus even though it may be abundant in the soil. Iron and manganese are most available in acidic soil, which is why acid-loving plants like blueberries evolved specialized root systems to absorb these micronutrients efficiently at low pH levels.
Calcium availability also depends heavily on pH. In strongly acidic soils, calcium leaches out rapidly and is not replaced quickly enough for heavy-feeding crops like tomatoes — a major contributing factor to blossom end rot. Magnesium follows a similar pattern, which is why Wicked Organics Epsom Salt (Magnesium Sulfate) is so valuable in acidic New England soils where both magnesium and sulfur run chronically low.
How to Test Your Soil pH
The most reliable method is sending a soil sample to your state cooperative extension lab or a commercial soil testing service. In New Hampshire, the UNH Cooperative Extension soil testing lab is the go-to resource. A professional test costs around $15-25 and provides not just pH but a full nutrient analysis with specific amendment recommendations tailored to your soil type. This is the gold standard — no home test kit matches the accuracy and detail of a professional lab analysis.
For a quick check at home, pH meters and chemical test kits from garden centers give reasonable readings that can guide basic decisions. Digital pH meters should be calibrated with buffer solution before each use for accuracy. Chemical test kits that use color-changing reagents are less precise but perfectly adequate for determining whether your soil is in the right general range.
To collect a representative sample, gather soil from 8-10 spots throughout your garden at 4-6 inch depth. Avoid unusual spots like directly under a compost pile or against a foundation wall. Mix all the sub-samples together in a clean bucket, let the composite dry for a day, and submit about 2 cups of the mixed sample. If you have distinctly different growing areas — a vegetable garden, a blueberry patch, and a lawn — test each area separately because their pH needs and current levels may be very different.
How To Store
Blueberries, azaleas, rhododendrons, hydrangeas for blue flowers, and evergreens often need lower pH than what naturally occurs in many garden soils. There are several Old Cobblers Farm products that lower soil pH as a secondary benefit while providing targeted nutrition.
Wicked Growth Ammonium Sulfate (21-0-0) is one of the most effective pH-lowering fertilizers available. It provides 21% nitrogen while the ammonium form undergoes nitrification in the soil — a microbial process that releases hydrogen ions, directly lowering pH. You get a nitrogen feeding and a pH adjustment in one application. For blueberry patches and evergreen beds where you need both nitrogen and lower pH, Ammonium Sulfate is the go-to product. Apply at 4-5 pounds per 1,000 square feet and water in thoroughly.
The Wicked Growth Blueberry Mix (10-10-10) is specifically formulated with acidifying ingredients for acid-loving plants. It delivers balanced nutrition while steadily pushing pH downward with every application. For gardeners growing blueberries, this is the simplest approach — one product handles both feeding and pH management.
On the organic side, Wicked Organics Blueberry Fertilizer (4-6-4) contains natural sulfate of potash and ammonium sulfate to lower pH while providing balanced organic nutrition. The organic matter in this blend also supports the acidic soil biology that blueberries and other ericaceous plants depend on — the mycorrhizal fungi that colonize their roots thrive in acidic, organic-rich soil.
For established blueberry patches and evergreen beds, consistent use of these acidifying fertilizers each season gradually brings pH into the target range and maintains it there. This is more effective than a one-time dramatic adjustment because it combines routine feeding with steady pH management, and it avoids the stress that rapid pH swings cause to soil biology and plant roots.
Lowering Soil pH With Old Cobblers Farm Products
Most vegetable gardens, lawns, and flower beds perform best at pH 6.0-7.0. If your soil tests below this range, calcium-containing fertilizers help nudge pH upward while delivering essential nutrients. This approach is more nuanced than simply dumping a pH amendment — you are feeding your plants and adjusting pH simultaneously.
Wicked Organics Bone Meal (3-15-0) supplies significant calcium that gently buffers soil acidity over time while providing the phosphorus that new plantings, bulbs, and root crops need. Each application contributes calcium carbonate equivalents that slowly neutralize excess acidity. For gardeners who apply Bone Meal at planting time year after year, the cumulative effect is a gradual, stable pH increase that avoids the shock of sudden adjustment.
Wicked Organics Bone Char (0-16-0) offers the same calcium-based pH buffering with even higher phosphorus concentration, plus the soil-conditioning benefits of activated carbon. The carbon structure in Bone Char acts as a pH buffer itself, helping to moderate swings in either direction. This makes it a dual-purpose amendment: phosphorus nutrition and pH stability.
Wicked Organics Greensand (0-0-3) provides a mild buffering effect that helps stabilize pH regardless of which direction it tends to drift. Its complex mineral composition acts as a natural pH moderator over time, preventing the dramatic swings that stress plants and disrupt soil biology. Greensand is not a strong pH adjuster — it is a stabilizer that keeps your soil in a consistent range once you get it there.
pH Preferences by Plant Category
Understanding which pH range your plants prefer lets you group them strategically in your garden and choose fertilizers that maintain the right conditions for each group.
Strongly acidic (pH 4.5-5.5): Blueberries, cranberries, azaleas, rhododendrons, mountain laurel. These plants have specialized root systems — they lack traditional root hairs and instead depend on ericoid mycorrhizal fungi to absorb nutrients. These fungi function best in acidic, organic-rich soil. Feed with Wicked Growth Blueberry Mix or Wicked Organics Blueberry Fertilizer (4-6-4) — both actively maintain low pH with every application. Supplement with Ammonium Sulfate (21-0-0) if pH is not dropping fast enough.
Moderately acidic (pH 5.5-6.5): Most evergreens, potatoes, strawberries, raspberries, hydrangeas for blue flowers. This range provides good availability of most nutrients while keeping iron and manganese accessible. Wicked Growth Evergreen Fertilizer (10-10-10), Wicked Growth Strawberry Fertilizer (10-5-13), and Wicked Growth Seed Potato Fertilizer (8-16-16) all work well in this range. Ammonium Sulfate can help maintain acidity if your soil trends toward neutral.
Slightly acidic to neutral (pH 6.0-7.0): Tomatoes, peppers, lettuce, herbs, most lawn grasses, roses, fruit trees, asparagus, corn, beans, peas. This is the sweet spot for the vast majority of garden plants — it is where the greatest number of nutrients are simultaneously available. Bone Meal and Bone Char applications help maintain this range in soils that trend acidic from rainfall and nitrogen fertilizer applications.
Raising Soil pH With Old Cobblers Farm Products
The smartest approach to pH management is choosing fertilizers that move pH in the direction you need while feeding your plants at the same time. This eliminates the need for separate pH amendments and simplifies your gardening routine.
If you grow blueberries and need lower pH, make Wicked Growth Ammonium Sulfate and the Blueberry formulas your primary nitrogen sources for that area. Every application feeds and acidifies simultaneously. Over 2-3 seasons of consistent use, pH gradually settles into the target range.
If your vegetable garden runs acidic (common in New England where rainfall steadily leaches calcium from the soil), Wicked Organics Bone Meal at planting time adds calcium that gently raises pH with each application. Bone Char mixed into beds provides longer-lasting pH buffering. Using these products consistently is a more sustainable approach than periodic large corrections.
Wicked Organics Epsom Salt (Magnesium Sulfate) supplies magnesium — commonly deficient in acidic New England soils — without significantly altering pH in either direction. This makes it safe to use in any pH situation. Apply 1-2 tablespoons per gallon as a foliar spray for fast correction of magnesium deficiency symptoms (interveinal yellowing), or broadcast 1-2 pounds per 100 square feet and water in for soil-level supplementation.
Test soil pH every 2-3 years and let the results guide which Old Cobblers Farm products you reach for. Over time, consistent fertilizer selection aligned with your pH goals eliminates the need for dramatic corrections and keeps your soil in the optimal range for whatever you are growing.