What is soil pH?
pH is a measure of how acidic or basic (alkaline) something is. Soil pH tells us how acidic or basic the soil is and is measured on a scale from 0 to 14.
- Neutral: A pH of 7 is neutral, like pure water.
- Acidic: Below 7 means the soil is acidic.
- Basic/Alkaline: Above 7 means the soil is basic or alkaline.
Most garden plants prefer a pH between about 6.0 and 7.5, but some plants like more acidic soil, others like more alkaline soil.
Why soil pH matters
- Nutrient Availability: pH changes how easily plants can get nutrients like nitrogen, phosphorus, and potassium from the soil.
- Bacteria and soil life: Microbes that help plants grow work best at certain pH levels.
- Plant health: If the pH is far from what a plant needs, it can grow poorly or look sick.
How to test soil pH
- Get a simple pH test kit from a garden store or online (or use a digital pH meter).
- Take a small sample of soil from a few inches deep in a few spots around your garden. Mix them together in a clean container.
- Follow the kit’s instructions to test the sample. You’ll see a color or a number that tells you the pH.
- Compare your result to the ideal range for your plants.
What to do if your soil isn’t in the right range
- If soil is too acidic (low pH): You can add ground limestone or lime to raise the pH over time. This helps nutrients become available to plants.
- If soil is too basic (high pH): You can add elemental sulfur or acidic compost to lower the pH gradually.
- Timing is important: Changes take weeks to months, not days, so plan ahead for planting seasons.
- Test again: After making changes, test the soil again to see if you’re close to the target pH.
Simple example for a 12-year-old gardener
Suppose you’re growing blueberries, which like acidic soil around pH 4.5–5.5. If your test shows pH 6.5, you’d need to lower it a bit by adding sulfur and by using acidic mulch like pine needles. For a tomato plant, you might prefer pH 6.0–6.8, so a pH 6.5 is usually great—no changes needed.