Pesticide history and the soil under former farms
Source: USGS NAWQA EPest · USGS
107,742 county-level records. Especially relevant on former orchard land.
What it is
The federal record
Pesticide data in the federal record represents county-level ambient indicators of agricultural chemical application — not site-specific measurements. The USGS NAWQA Pesticide National Synthesis Project tracks 107,742 records across the country. Unlike point sources, this data reflects the cumulative agricultural chemical footprint of an area. Historic organochlorine pesticides (DDT, chlordane, dieldrin) can persist in soil for decades after application stopped. Lead arsenate, used widely as an insecticide before the 1940s, persists essentially permanently — and former orchard land in apple-growing regions is the single highest-flag context.
Key facts
At a glance
County records
107,742
USGS NAWQA EPest
Analysis radius
County
Growable Ground
Severity tier
Moderate
Growable Ground
Why it isn't a verdict
The constructive read
Pesticide data reads as a screening signal rather than a verdict. County-level records tell you where the agricultural footprint is heaviest; they don't measure the soil under your feet. Site-specific testing closes the gap, and the test is widely available at low cost. Former orchard land warrants the test more than any other land-use history. For anyone gardening on former farmland, organic matter additions and cover crops help bind and sequester residual pesticide compounds in soil over time. Modern pesticides break down faster than the legacy chemicals, so newer agricultural land has a different — usually shorter — fingerprint.
What to do
The playbook
If you garden on former agricultural or orchard land, test soil for lead arsenate and persistent organochlorine compounds. State extension offices typically offer the panel at low cost. Use the county-level data as a screening tool that prompts the test, not as a substitute for it. Raised beds with imported clean soil over a geotextile barrier eliminate the soil-contact pathway entirely. Cover crops and high organic matter additions help over time. Modern pesticide applications (post-2000) typically use compounds that break down faster than legacy chemicals — orchard land predating the 1940s is the highest-priority test.
Mitigation steps
Concrete moves, in order
- 1If gardening on former agricultural or orchard land, test soil for lead arsenate and organochlorine pesticides.
- 2County-level data is a screening indicator — site-specific soil testing is needed to confirm actual contamination.
- 3Raised beds with clean imported soil eliminate the soil-contact pathway for historic pesticide residues.
- 4Cover crops and organic matter additions can help bind and sequester residual pesticide compounds in soil.
- 5Modern pesticide applications (post-2000) generally use compounds that break down faster than legacy chemicals.
Frequently asked questions
Should I test soil before gardening on former farmland?
If the land was used for agriculture or orcharding before 1970, yes. Organochlorine pesticides (DDT, chlordane) persist for decades; lead arsenate persists essentially permanently. State extension offices typically run the test at low cost.
What's lead arsenate, and why does it matter for gardens?
Lead arsenate was a pre-1940s insecticide used widely in apple orchards. It contains both lead and arsenic, both of which persist in soil indefinitely. New plantings on former apple-orchard land are the highest-priority context for soil testing in the entire pesticide category.
Are modern pesticides as persistent as the historic ones?
No. Most modern pesticides are designed to break down within weeks or months of application. The persistent legacy compounds — DDT, chlordane, dieldrin — were largely phased out by the 1980s in the US. Land farmed only since the 1990s has a substantially shorter chemical fingerprint than mid-century farmland.
See what's near your land
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