Marshall County Soil Data
Marshall County, Iowa
USDA SSURGO / PHZMAvg pH
6.4
Texture
Loam
Drainage
Moderately well drained
Organic Matter
3.2%
Hydrologic Group
B
Data Story
About Soil in Marshall County, Iowa
Prairie 'Black Gold' in Marshall County
Marshall County features Mollisols—the iconic 'black gold' of the prairie—with a pH of 6.43 that perfectly matches the Iowa state average. This loam texture is highly sought after for its natural fertility and balanced chemical profile.
The Goldilocks of Soil Composition
A balanced blend of 50.2% silt, 26.0% sand, and 23.8% clay makes this soil exceptionally workable and productive. This mix provides enough clay for nutrients, enough silt for water, and enough sand for drainage.
Reliable Water and Organic Matter
Organic matter measures 3.22%, which is lower than the state average but remains very healthy compared to national figures. The available water capacity of 0.185 inches per inch ensures a steady supply of moisture for thirsty crops.
Excellent Infiltration and Low Runoff
The soil is moderately well-drained and carries a hydrologic group B rating, indicating good infiltration and low runoff. This makes Marshall County's land versatile for everything from high-yield corn to residential development.
A Prime Spot for Heirloom Crops
Sitting in hardiness zone 5a, this county is a prime location for heirloom tomatoes and cool-weather crops like broccoli. Take advantage of some of the state's most iconic soil and start your growing project today.
Soil Composition
Soil pH
Soil Series
Detailed soil series data not yet available for this county.
Hydrologic Group
Group B — Moderate Runoff
Moderately deep, moderately well-drained soils with moderate infiltration rates. Good balance of drainage and water retention.
Drainage Class
Moderately well drained
Water is removed somewhat slowly. May have a slowly permeable layer or seasonal water table.
Soil Profile
Dominant texture: 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 Marshall County have?
Marshall County's soil is classified as Loam. This indicates the relative proportions of sand, silt, and clay — 26% sand, 50% silt, and 24% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Marshall County's soil acidic or alkaline?
Marshall County's soil has a pH of 6.4, which is moderately acidic. This range suits many crops and is common across much of the eastern US.
What is the drainage class for Marshall County?
Marshall County has a dominant drainage class of "Moderately 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 Marshall County's soil?
Based on Marshall County's Loam texture, pH of 6.4, and Moderately 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 Marshall County?
Marshall 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: Marshall County
Soil Verdict
Marshall 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
Marshall County closely matches the Iowa average hardiness conditions. The zone range of 5a-5b within the county means soil and planting decisions should account for local elevation and topography.
Planning your lawn? View lawn care data for Marshall 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.