Putnam County Soil Data
Putnam County, Indiana
USDA SSURGO / PHZMAvg pH
6.2
Texture
Silt loam
Drainage
Well drained
Organic Matter
2.3%
Hydrologic Group
D
Data Story
About Soil in Putnam County, Indiana
Putnam's Silt Loam Inceptisols
Putnam County features an average pH of 6.21, which is healthier than the state average of 6.08 but slightly below the national 6.5 median. These Inceptisols are categorized as silt loams, representing a balanced and versatile soil type. It provides a reliable foundation for the county's diverse agricultural landscape.
Silt-Heavy Soils for Moisture Retention
The composition includes 19.6% sand, 64.0% silt, and 16.4% clay. This silt-dominant mix creates a flour-like texture that is excellent for retaining the moisture plants need during dry spells. However, the low sand content means the soil can become compacted if driven over when wet.
Solid Potential and High Water Storage
With 2.33% organic matter, Putnam exceeds the national 2.0% average but trails the 4.90% state benchmark. Its available water capacity of 0.214 inches per inch is higher than the state average of 0.202. This high storage capacity helps crops survive the heat of an Indiana July without immediate stress.
Well-Drained Ground with Infiltration Limits
The soil is classified as well drained, yet it falls into hydrologic group D, which indicates low infiltration rates when saturated. This means that while the surface dries quickly, the deeper layers can resist downward water movement. It is an ideal setup for many types of farming but requires careful planning for septic systems.
Diverse Gardening in Zone 6a
USDA Hardiness Zone 6a allows for a wide variety of vegetables, from peppers to pumpkins. The silt loam is especially good for root vegetables that appreciate a consistent moisture supply. Your Putnam garden will thrive with a bit of extra compost to boost its natural organic levels.
Soil Composition
Soil pH
Soil Series
Detailed soil series data not yet available for this county.
Hydrologic Group
Group D — High Runoff
Clay soils with very slow infiltration rates. Highest runoff potential. These soils have a permanent high water table or are shallow over impervious material.
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 Putnam County have?
Putnam County's soil is classified as Silt loam. This indicates the relative proportions of sand, silt, and clay — 20% sand, 64% silt, and 16% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Putnam County's soil acidic or alkaline?
Putnam 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 Putnam County?
Putnam 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 Putnam County's soil?
Based on Putnam County's Silt 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 Putnam County?
Putnam County's dominant soil order is Inceptisols. Inceptisols are young soils with weak horizon development. They occur in a wide range of climates and parent materials.
Soil & Planting Advisory: Putnam County
Soil Verdict
Putnam County is in USDA hardiness zone 6a, a moderate climate zone. where winter lows can reach -10°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
Putnam County closely matches the Indiana average hardiness conditions.
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Other Counties in Indiana
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.