Union County Soil Data
Union County, Iowa
USDA SSURGO / PHZMAvg pH
6.3
Texture
Silt Loam
Drainage
N/A
Organic Matter
3.1%
Hydrologic Group
N/A
Data Story
About Soil in Union County, Iowa
Acidic Foundations in Union County
The average soil pH here is 6.28, which is slightly more acidic than the statewide average of 6.43. While specific taxonomic data is missing, this acidity is characteristic of many productive Southern Iowa fields.
High Silt and Balanced Clay
With 52.4% silt and 26.7% clay, the soil provides a dense medium for root development. The 20.9% sand content helps maintain some porosity, though the high silt levels dominate the soil's behavior.
Consistent Moisture for Crops
The soil holds 0.201 inches of water per inch, beating the state average of 0.195. Organic matter levels are 3.14%, offering a healthy environment for beneficial soil microbes and worms.
Steady Hydrology and Deep Silt
Though formal drainage classes aren't specified, the silt-heavy mix suggests moderate water retention. This provides a buffer against dry weather, though it may take longer to dry out in the spring.
Planting Pride in Zone 5b
Union County's 5b zone is perfect for everything from sweet corn to heirloom tomatoes. Take advantage of the above-average water capacity to grow a lush, productive backyard garden.
Soil Composition
Soil pH
Soil Series
Detailed soil series data not yet available for this county.
Hydrologic Group
Hydrologic group data not available.
Drainage Class
Drainage class data not available.
Soil Profile
Dominant texture: Silt Loam
Typical soil profile. Actual depths vary by location.
USDA Soil Orders
Soil Amendment Products
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Browse Soil AmendmentsFrequently Asked Questions
What type of soil does Union County have?
Union County's soil is classified as Silt Loam. This indicates the relative proportions of sand, silt, and clay — 21% sand, 52% silt, and 27% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Union County's soil acidic or alkaline?
Union County's soil has a pH of 6.3, which is moderately acidic. This range suits many crops and is common across much of the eastern US.
What is the drainage class for Union County?
Drainage class data is not currently available for Union County.
What crops or plants grow well in Union County's soil?
Based on Union County's Silt Loam texture, pH of 6.3, and drainage class, the soil is well suited for vegetables, grains, and most field crops, row crops and vegetable gardens.
What USDA soil order is found in Union County?
The dominant USDA soil order for Union County is not currently available in our dataset.
Soil & Planting Advisory: Union County
Soil Verdict
Union County is in USDA hardiness zone 5b, a cold climate zone. where winter lows can reach -15°F. Freeze-thaw cycles are moderate; soil biology slows in winter but recovers reliably in spring, supporting a broad range of plants.
Planting Guidance
A wide plant palette is possible: deciduous trees, most shrubs, cool-season vegetables, and many perennials thrive here. Winter protection (mulch, burlap wraps) helps push the zone boundary for desired species. Always match plant selections to the specific microclimate of your property — low spots, slopes, and wind exposure can shift effective hardiness by half a zone.
Soil Implications
Moderate freeze-thaw cycles naturally aerate the soil but can also cause compaction in clay-heavy areas; annual core aeration is beneficial. Organic matter amendments decompose at a moderate pace — aim for 3-5% organic content for optimal fertility. When soil temperatures drop below freezing, microbial nitrogen cycling stops; spring fertilization is more effective than late-fall application.
Regional Context
Union County closely matches the Iowa average hardiness conditions.
Planning your lawn? View lawn care data for Union County on LawnByCounty.com →
Other Counties in Iowa
Soil data sourced from USDA SSURGO via Soil Data Access. Data is informational only and should not be used as a substitute for on-site soil testing. Contact your local NRCS office for site-specific soil information.