Ap — 0–18 cm  |  Silt loam  |  OM 1.5%  |  Db 1.4 g/cc
Bt1 — 18–25 cm  |  Silty clay loam  |  OM 0.5%
2Bt2 — 25–48 cm  |  Clay  |  Frag 11%  |  Db 1.4
3Bt3 — 48–89 cm  |  Channery loam  |  Frag 45%
BC — 89–114 cm  |  Gravelly loam  |  Restriction depth: 114
C — 114–150 cm  |  Loamy gravel  |  AWC 0.09
2C — 150–180 cm  |  Sandy gravel  |  Paralithic contact
R — Lithic bedrock  |  SOC calculation ends here
SSURGO Data Journalism

The World
Beneath

What happens when you ask America's most comprehensive soil database to tell its story. More than 22,000 named soil series. 50 states. Centuries of buried carbon, hidden drought resilience, and the unexpected science written in dirt.

Published June 1, 2026 Soil Data Access Project Soil Survey Data & Analysis
22K+Soil Series
56States & Territories
254SQL Scripts
~100BTons Soil Carbon, US
Scroll to read
Chapter I The Carbon Bank

A Single Field.
3,327 Grams of Carbon Per Square Meter.

Deep in Dane County, Wisconsin, sits a soil map unit with the unglamorous identifier mukey 2809839. It covers a few thousand acres of rolling farmland, unremarkable to the eye. But run a SQL query against SSURGO and something extraordinary emerges.

The top 18 centimeters alone — the Ap horizon — lock away 1,874 grams of carbon per square meter. Add the underlying clay layers, and the full profile sequesters more than 3,327 g/m². That's the equivalent of burning about 1.8 liters of gasoline — stored, quietly, in a patch of ground the size of a welcome mat.

"Soil is the largest terrestrial carbon sink on the planet. We can measure it, horizon by horizon, with a single SQL query."

The calculation — organic matter concentration, multiplied by bulk density, multiplied by horizon thickness, corrected for rock fragment volume — has been standardized into the SSURGO database. Every one of America's 300+ million soil map unit acres has a number waiting to be computed.

Formula: SOC = ((Hz_thickness × (OM/1.724 × Db)) / 100) × ((100 − FragVol) / 100) × ComponentPct × 100  [g/m²]

Soil Profile — Dane County, WI  ·  mukey 2809839
SOC Equation: ( thickness × (OM/1.724 × Db) / 100 ) × (frag_corr) × compPct Total: — g/m²
0 g/m²
Formula Components
OM / 1.724
Organic matter → organic carbon (Van Bemmelen factor)
× Db (g/cc)
Bulk density → converts volume to mass
× Hz_cm
Horizon thickness → depth zone (0–20, 20–50, 50–100)
/ 100
% → decimal conversion
× (1 − frag/100)
Rock fragment correction → soil only, not rocks
× compPct × 100
Component weight → map unit proportional stock
Chapter II The Food Score

A Number Between 0 and 100
Determines Where America Eats

The National Commodity Crop Productivity Index (NCCPI) scores every soil's ability to grow corn and soybeans on a scale from 0 to 1. It is, in the simplest terms, a number that determines agricultural destiny.

The Fargo clay soils of the Red River Valley — formed in the bed of ancient glacial Lake Agassiz, fine-textured and extraordinarily fertile — score 0.87. The desert soils of the Sonoran Basin, alkaline and shallow, score 0.03.

The SQL query behind NCCPI (ver 3.0) pulls from cointerp, normalizes within each MLRA using min/max breakpoints, then slices the range into 20 equal productivity classes. It is an entire agricultural economy, queryable from a single SELECT statement.

"North Dakota's best soils score 87. Arizona's score 3. The difference is geological time, compressed into a decimal."

Query: NCCPI_MLRA.sql · Joins: legend → mapunit → muaoverlap → laoverlap → component → cointerp · Key fields: interphr (rating value), mrulename = 'NCCPI – National Commodity Crop Productivity Index (Ver 3.0)'

NCCPI Score — Fargo Clay, ND
0
out of 100
87
Fargo Clay · ND
Red River Valley
3
Desert Soil · AZ
Sonoran Basin
Chapter III The Drought Architecture

How Much Rain Can
Your Soil Save?

0–20 cm
0.0"
stored
20–50 cm
0.0"
stored
50–100 cm
0.0"
stored
100–150 cm
0.0"
stored
0.0"
Total Available Water Storage (0–150 cm) · Fine Loam, Midwest

Available Water Storage (AWS) is the total amount of plant-available water a soil can hold — the hydraulic buffer between a failed harvest and a successful one.

Computed by multiplying available water capacity (AWC, in cm/cm) by horizon thickness for each depth zone, the AWS calculation in SSURGO reaches down to 150 cm. A well-structured fine loam in the Corn Belt can hold 8–10 inches of plant-available water from 0–150 cm. A shallow, rocky soil might hold just 1–2 inches.

The 2012 drought — the worst in 50 years for US agriculture — caused $30B in crop losses. Soils with high AWS stored enough subsoil moisture to buffer corn through the critical pollination window. The AWS number, encoded in every SSURGO map unit, predicts resilience.

The SQL query computes AWS across four depth zones (0–20, 20–50, 50–100, 100–150 cm) using the #acpf and #aws150 temp tables, carefully accounting for restriction depths — fragipans, lithic contacts, and duripans that cut the effective root zone short.

AWS formula: Σ (InRangeBot − InRangeTop) × AWC_r  [cm water per depth zone]

Chapter IV The Fragility Crisis

Measured Across America:
Real SSURGO Data

Every figure on this chart is real. Derived from SSURGO soil-property interpretation records spanning every US state and territory, averaged to the state level across two measurements: the Fragile Soil Index (FSI) — how vulnerable a soil is to degradation — and the Organic Matter Depletion risk (OM).

Nevada's soils score 0.50 FSI. Half of the state's soils sit at the threshold of serious fragility. Arizona is at 0.48. New Mexico at 0.39. These are arid Western landscapes where thin, erodible soils formed over millennia in climates that provided little biological protection.

More alarming is the OM Depletion story. Arizona leads at 0.88 — meaning 88% of soil interpretations show high organic matter depletion risk. Texas comes in at 0.83. Oklahoma at 0.80. These are not just fragile soils; they are soils actively losing their carbon.

Meanwhile, Maine (FSI: 0.10), New Hampshire (0.16), and Vermont (0.17) sit in the lower-left quadrant — resilient, forest-protected, carbon-rich soils. Alaska's soils, while cold, score an FSI of 0.12 across 10,000+ observations.

The Corn Belt — Iowa, Illinois, Indiana — occupies a critical middle zone. FSI values around 0.30 are moderate, but these states have the most cropland acres and the highest OM depletion pressure. Iowa's OM score of 0.60 means decades of tillage have drawn down the carbon bank.

The dual threat: States with both high FSI AND high OM depletion have soils that are fragile and losing the one property (organic matter) that protects against fragility. This feedback loop is the central regenerative agriculture crisis of our time.

Resilient · Low OM Loss
Fragile · Low OM Loss
Resilient · High OM Loss
Fragile · High OM Loss
⚠ CRISIS ZONE
Fragile Soil Index vs. Organic Matter Depletion Risk by State
High fragility + high OM loss High OM loss Lower risk Bubble size = number of interpretations
Source: SSURGO interpretations extract · Rules: Fragile Soil Index, SOH – Organic Matter Depletion · State means weighted by map unit component
Top 20 States — Fragile Soil Index (Mean Score, 0–1)
Fragile Soil Index OM Depletion Risk
Source: SSURGO interpretations · 56 states & territories · Averaged by state symbol (first 2 chars of areasymbol)
Chapter V The Unexpected Database

What Else Did We Find
in the SQL Scripts?

The 254 SQL scripts in this library tell stories far beyond crop productivity and erosion risk. Buried in the sandbox are queries that reveal how soil science touches — and measures — almost everything.

🍄
🍄

Where Morels Grow

A SQL query can identify soils that match the precise physical and chemical conditions where morel mushrooms fruit. The script checks five independent soil properties and flags any map unit meeting all criteria.

Sand: 30–80%  ·  Silt: 30–50%
Clay: 8–25%  ·  OM: 2.8–5.0%
pH: 6.0–7.5  ·  Drainage: Well drained
Source: Morel_Mushrooms_Suitability.sql · MN, WI, IA
⚾
⚾

Baseball Infield Soil

Professional groundskeepers and soil scientists share a language. The specific sand content, silt-to-clay ratio, and medium-sand fraction that defines a legal infield mix exists in SSURGO — and can be queried nationwide.

Sand: 60–65% (total)
Silt:Clay ratio: 0.75–1.0
Med-sand fraction: ≥ 50% of sand
Source: Baseball_Infield_Soil_Soruce.sql
🕳️
🕳️

Karst Sinkhole Risk

Where limestone, dolomite, or gypsum parent material meets acidic infiltrating water, the ground dissolves. The Karst SQL assigns probability scores from 0 to 1 based on parent material origin and soil taxonomy, identifying where sinkholes are geologically probable.

Residuum limestone: 0.5
+ pale taxonomic group: → 0.1
+ "karst" in local phase: → 0.8
Rock gypsum/halite: 1.0 (highest)
Source: Karst.sql · Joins: copmgrp → copm → component
3,327
g/m² SOC
Full profile, WI Dane County
0.50
Max FSI
Nevada — most fragile state mean
0.88
OM Depletion
Arizona — highest mean risk
1.0
Karst Risk
Rock gypsum / rock halite
87
NCCPI Score
Fargo Clay — Red River Valley
Chapter VI Conservation Mathematics

Every Cover Crop Acre
Reduces Carbon Dioxide

This analysis joins land management practice records with emission factors, creating a county-level ledger of greenhouse gas reductions from regenerative land practices.

Cover Crop (Practice 340) reduces net GHG by an average of –0.18 t CO₂eq/acre/year through soil carbon sequestration. No-Till (Practice 329) delivers –0.22 t CO₂eq/acre/year. Nutrient Management (Practice 590) prevents N₂O emissions at –0.15 t CO₂eq/acre/year.

These numbers come from USDA's own climate modeling tools, connected to field-level practice data through state-county codes.

"Connecting emission factors with applied acres — creating a county-level carbon ledger that can account for every acre of conservation work."
Regenerative Ag Composite Score
Score = (1 − FSI) × (1 − OM depletion) × 100 — all 51 states ranked. Higher = healthier, more resilient soil.
Source: SSURGO FSI + OM means · Score = (1−FSI)×(1−OM)×100
Chapter VII What Comes Next

Where This Work
Needs to Go

This database is extraordinary — and incomplete. The SQL scripts in this repository reveal a system that can answer almost any soil science question, given the right connection points. Here is what is missing, and why it matters.

Live SSURGO Map (PMTiles)

Exact SSURGO polygon boundaries streaming at zoom 12+ via PMTiles. 58 state layers, no simplification. Live at the Regenerative Ag Risk Map.

County Risk Leaderboard

All 4,089 survey areas ranked by combined FSI + OM depletion score. Sortable, filterable, linked to the map. View leaderboard →

Linked Scatter + Map Explorer

Brush the FSI × OM scatter plot to highlight counties on the national map. Bidirectional — click a county on the map to highlight its dot. Open Explorer →

State FSI Ridgeline Chart

KDE-smoothed Fragile Soil Index distributions for all 51 states, sorted from Maine (most resilient) to Arizona (most fragile). View Ridgeline →

Dorling Cartogram

Force-layout state bubbles sized by survey area count, colored by mean FSI. Preserves geographic relationships while eliminating western-state distortion. View Cartogram →

Real-Time SDA Queries + Find My Soil

Live SDA API calls embedded in the visualization layer. The "My Soil" button geolocates and returns the exact map unit, FSI class, and national percentile for any point. Try it →

Fragile Soil + OM Depletion Map

County-level choropleth with PMTiles map unit detail at zoom 9+. The exact interactive map described here — now live at the national scale. Open Map →

SDA SQL Training Site

A complete beginner-to-expert SQL curriculum with live queries running against real SSURGO data. 8 tracks, 35+ lessons, query history, progress tracking. Open Training →

National SOC Raster (30 m)

A pixel-by-pixel soil organic carbon map at 30-meter resolution would transform this from a polygon tool into a field-level carbon accounting system. Pre-computation from SSURGO + KSSL lab data is feasible.

NCCPI National Layer

NCCPI values exist in SSURGO for every map unit but have not been rendered as a national raster. A county-normalized NCCPI map would be the definitive food security risk layer.

KSSL Lab Data Integration

The Kellogg Soil Survey Lab holds 800,000+ measured samples — pH, CEC, carbon, particle size. Joining to SSURGO map units would show measured vs. modeled soil properties side by side.

Time-Series Regenerative Ag Index

SSURGO doesn't have dates — but KSSL does. Linking lab sample dates to SSURGO series would enable a decades-long trend line of US soil organic matter change.

"Soil data can predict mushroom habitat, sinkhole probability, drought resilience, and agricultural productivity — from a single SQL query against a publicly available database. We are only beginning to read it."
🗺 Regenerative Ag Risk Map 🌱 Regenerative Ag Risk Map 🔍 SQL Explorer 📖 Query Examples 🏠 Home 🔗 Run Queries on SDA

Data: USDA SSURGO · Interpretations · KSSL
Visualizations derived from SSURGO soil interpretation data across 56 US states and territories.
github.com/jneme910/NRCS-Soil-Data-Access
Reference: Statistics for Soil Survey · NCSS-Tech