Articles
Soil rankings and maps
The same USDA soil survey numbers behind every county page, compared across the whole country.
- Soil pH by state
Every state ranked by typical topsoil pH, from the acidic Northeast to the alkaline desert West.
- The 25 US counties with the most acidic soil
Where topsoil is most acidic county by county, and what that means for lime, lawns and blueberries.
- The 25 US counties with the most alkaline soil
The counties with the most alkaline topsoil, and why iron-hungry plants turn yellow there.
- Where the US has the most clay soil
The states and counties where clay topsoil dominates, from the Mississippi Delta to the Dakota plains.
- Where the US has the most sandy soil
Florida, the Nebraska Sandhills and the Carolina coastal plain: where sandy topsoil dominates.
- Where soil is best for septic systems
Most US land is rated very limited for septic fields. These counties have the most land that is not.
- Where the US has the wettest, most poorly drained soil
Soggy yards and wet basements: the states and counties where most soil is naturally poorly drained.
- The 25 US counties with the most flood-prone soil
Where the soil survey says land floods most often, led by coastal Louisiana parishes.
- The 20 most common types of soil in the US
The named soils that cover the most American land, from Nebraska's Valentine sand to Georgia's Cecil clay.
- The most common soil in every US state
One soil per state: the named series that covers the most ground in each of the 50 states and DC.
- Where rain soaks into the soil slowest, and fastest
Runoff, puddles and rain gardens: the places where soil takes in rain slowest and fastest.
- Where the US has the most organic matter in its topsoil
Dark, carbon-rich topsoil: where it is most common, and why the very top of the list is swamp.
- The 25 US counties with the steepest land
Where the typical acre is on a hillside, led by the coalfields of Appalachia.
- The soil under America's 25 most populous counties
Los Angeles, Cook, Harris and the rest: what the soil survey says is under the biggest metro counties.
- Where the US has expansive, shrink-swell clay soil
The cracking clays that heave foundations: which states have the most, and the soils to know by name.
- What should I add to my garden soil?
Sand, mulch, perlite, calcium, nitrogen, leaves, acid: what each does to garden soil, and when to skip it.
- How to get your soil tested, including free options
Extension labs, free testing seasons and days, how to take a good sample, and whether home kits are worth it.
- Does my soil have mold?
White fuzz, slime and mushrooms in soil and mulch: what is harmless, what hurts plants, and who should wear a mask.
- How soil is tested for construction, and why
Borings, blow counts and lab tests: how engineers check the ground before a building goes up.