Soil pH Map

The map shows USDA’s typical values for each map unit^[1]; test your own soil before acting on them. To change it, see how to raise or lower soil pH and its lime and sulfur calculator.

Reading the map

Each polygon is colored by the USDA reaction class of its dominant soil’s surface, from ultra acid (orange) through neutral (green) to very strongly alkaline (indigo)^[2]. USDA’s eleven reaction classes run from ultra acid, below pH 3.5, to very strongly alkaline, above 9.0, with neutral from 6.6 to 7.3^[2].

• ultra acid
• extremely acid
• very strongly acid
• strongly acid
• moderately acid
• slightly acid
• neutral
• slightly alkaline
• moderately alkaline
• strongly alkaline
• very strongly alkaline

Soil pH across the US

Acre-weighted across USDA’s classified US topsoil, surface pH splits across the reaction classes like this^[1]:

Where soils run acid or alkaline

By median topsoil pH, the five most acidic states are Maine, New Hampshire, Alabama, Massachusetts and Mississippi, and the five most alkaline are Utah, Nevada, Arizona, New Mexico and Texas^[1]. Many dry-country soils are Aridisols, with layers where calcium carbonate, salts or gypsum have accumulated^[3]; our page on Aridisols maps where they are found.

What your pH means for plants

pH matters because it controls which nutrients plants can take up. Oregon State University Extension puts most vegetables at 6 to 7, lawns at 5.5 to 6, and blueberries, azaleas and rhododendrons at 4.5 to 5.5, and says a soil test should decide whether to change it^[4].

The map tells you what to expect before you test. A vegetable bed on soil mapped well below pH 6, or blueberries on soil mapped above 7, are the cases where a test is most likely to call for a change^[4]; see how to raise or lower soil pH.

How this map is made

USDA records the pH of mapped soil layers, measured in a 1:1 mix of soil and water, as a typical value with a low and a high^[1]. The map colors each map unit by its main soil’s surface value, sorted into the reaction classes^[2]. National shares are weighted by acres across classified US topsoil, and a state’s median needs at least 500 soil components with a mapped surface pH. Full details are in the methodology.

Median topsoil pH by state

Acre-weighted median surface pH per state, among states with at least 500 components carrying a mapped surface pH, most acidic first^[1]:

Download the data: pH reaction classes (CSV), median pH by state (CSV). Aggregated from USDA SSURGO; data generated 2026-10-07. See the methodology.

Frequently asked questions

Where is soil most acidic in the US?

By acre-weighted median surface pH, the most acidic topsoils are in Maine and New Hampshire (median pH 4.8)^[1].

Where is soil most alkaline in the US?

The most alkaline topsoils are in the dry West, led by Utah (median pH 8.2)^[1]. Many soils of dry regions are Aridisols, with subsurface layers where calcium carbonate, salts or gypsum have built up^[3].

What pH do plants need?

Oregon State University Extension puts most vegetables at a pH of 6 to 7, lawns at 5.5 to 6, and acid-loving blueberries, azaleas and rhododendrons at 4.5 to 5.5^[4].

What is the pH of my soil?

Search your address on the map above to see USDA’s mapped topsoil pH for the soil there. It is the typical value for the map unit, so test your own soil with a meter or a lab before you treat it^[1][4].

Sources

1. USDA NRCS, Soil Survey Geographic Database (SSURGO), via Soil Data Access
2. USDA NRCS, National Soil Survey Handbook, Part 618, section 618.53: Reaction (pH) classes
3. University of Idaho, College of Agricultural and Life Sciences, Soil Orders: Aridisols
4. Oregon State University Extension, Why soil pH matters, and how to manage it in your garden