Franklin County Soil Data
Franklin County, Iowa
USDA SSURGO / PHZMAvg pH
6.7
Texture
Silt loam
Drainage
Well drained
Organic Matter
4.9%
Hydrologic Group
C
Data Story
About Soil in Franklin County, Iowa
High-Performance Mollisols in Franklin
Franklin County boasts a soil score of 77.0, significantly higher than the Iowa average. Its Mollisols have a pH of 6.68, which is slightly more alkaline than the national median of 6.5.
Silky and Rich Silt Loam
Silt Loam is the dominant texture, featuring a high 46.0% silt content and 22.8% clay. The 30.0% sand component keeps the soil aerated and prevents the heavy compaction often found in clay-heavy regions.
Exceptional Organic Matter Levels
The county features a massive 4.91% organic matter content, dwarfing the national 2.0% average. Its available water capacity of 0.195 in/in perfectly matches the state average, ensuring consistent moisture for crops.
Well Drained with Slow Infiltration
The land is well drained but falls into Hydrologic Group C, which indicates a slower infiltration rate. This makes the soil highly effective at retaining nutrients while still preventing surface waterlogging.
A Gardener's Paradise in Zone 5a
From pumpkins to sweet corn, Franklin County's rich soil supports a diverse range of Zone 5a crops. The high organic content provides a natural boost that any home garden will appreciate.
Soil Composition
Soil pH
Soil Series
Detailed soil series data not yet available for this county.
Hydrologic Group
Group C — Moderate-High Runoff
Soils with slow infiltration rates, often with a layer that impedes downward water movement. Higher clay content restricts drainage.
Drainage Class
Well drained
Water is removed from the soil readily but not rapidly. Optimal for most plants and construction.
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 Franklin County have?
Franklin County's soil is classified as Silt loam. This indicates the relative proportions of sand, silt, and clay — 30% sand, 46% silt, and 23% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Franklin County's soil acidic or alkaline?
Franklin County's soil has a pH of 6.7, which is near neutral. This range is ideal for most garden plants and field crops.
What is the drainage class for Franklin County?
Franklin County has a dominant drainage class of "Well drained." Well-drained soils allow excess water to move through quickly, reducing waterlogging risk and supporting most field and garden crops.
What crops or plants grow well in Franklin County's soil?
Based on Franklin County's Silt loam texture, pH of 6.7, and Well drained, the soil is well suited for vegetables, grains, and most field crops, row crops and vegetable gardens, most annual and perennial crops.
What USDA soil order is found in Franklin County?
Franklin County's dominant soil order is Mollisols. Mollisols are fertile, dark-colored soils that formed under grassland vegetation. They are among the most productive agricultural soils in the world.
Soil & Planting Advisory: Franklin County
Soil Verdict
Franklin County is in USDA hardiness zone 5a, a cold climate zone. where winter lows can reach -20°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. With extreme winter lows, any marginally hardy plants need heavy mulch and wind protection. 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
Franklin County closely matches the Iowa average hardiness conditions.
Planning your lawn? View lawn care data for Franklin 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.