Audubon County Soil Data
Audubon County, Iowa
USDA SSURGO / PHZMAvg pH
6.2
Texture
Silty clay loam
Drainage
Well drained
Organic Matter
3.0%
Hydrologic Group
C
Data Story
About Soil in Audubon County, Iowa
The Rich Mollisols of Audubon
Audubon County's soil belongs to the Mollisols order, characterized by a dark, fertile surface layer and a pH of 6.19. This pH is more acidic than the national median of 6.5, reflecting its prairie-derived heritage.
Heavy Silty Clay Loam Soils
Classified as silty clay loam, the soil contains 57.8% silt and 29.4% clay. The low 12.7% sand content means the soil holds nutrients tightly but can be difficult to work when wet.
Exceptional Reservoirs for Thirsty Crops
Organic matter stands at 3.04%, which is lower than the state average of 3.81% but still very productive. A high available water capacity of 0.210 in/in makes this soil an exceptional reservoir during dry weeks.
Well Drained with Moderate Runoff
These soils are well drained and fall into hydrologic group C. This combination means water moves through the profile effectively, though the group C rating suggests some runoff potential during heavy rains.
Moisture-Loving Perennials for Zone 5a
Gardeners in Zone 5a can take advantage of the high water capacity to grow lush leafy greens and moisture-loving perennials. Start a compost pile to boost that organic matter even further.
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: Silty clay loam
Typical soil profile. Actual depths vary by location.
USDA Soil Orders
Clay Soil Detected
Clay soils can struggle with drainage. These products improve soil structure and water flow.
Browse Soil AmendmentsFrequently Asked Questions
What type of soil does Audubon County have?
Audubon County's soil is classified as Silty clay loam. This indicates the relative proportions of sand, silt, and clay — 13% sand, 58% silt, and 29% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Audubon County's soil acidic or alkaline?
Audubon County's soil has a pH of 6.2, which is moderately acidic. This range suits many crops and is common across much of the eastern US.
What is the drainage class for Audubon County?
Audubon 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 Audubon County's soil?
Based on Audubon County's Silty clay loam texture, pH of 6.2, 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 Audubon County?
Audubon 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: Audubon County
Soil Verdict
Audubon 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
Audubon 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 Audubon 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.