Johnston County Soil Data
Johnston County, Oklahoma
Avg pH
6.2
Texture
Clay loam
Drainage
Moderately well drained
Organic Matter
1.5%
Hydrologic Group
D
Data Story
About Soil in Johnston County, Oklahoma
Acidic Alfisols of South-Central Oklahoma
Johnston County is defined by Alfisols, a taxonomic order known for being naturally productive but somewhat acidic. The average pH of 6.20 is slightly higher than the state average but remains below the national median of 6.5. This chemical profile generally supports healthy pasture and woodland growth.
The Balanced Grip of Clay Loam
With a dominant clay loam texture, the soil features 42.1% sand, 30.9% silt, and 22.5% clay. This high clay content compared to neighboring counties provides excellent nutrient retention and structural stability. It is a dense mix that holds onto fertilizers well but can be heavy to work when wet.
Reliable Moisture for Local Crops
The soil’s available water capacity of 0.144 in/in exactly matches the Oklahoma state average. Organic matter stands at 1.47%, which is lower than the 1.72% state average and the 2.0% national benchmark. Despite lower organic levels, the clay-heavy texture helps preserve the nutrients that are present.
Steady Moisture and Slow Infiltration
The land is moderately well drained, providing a safe balance for most agricultural uses. However, it belongs to hydrologic group D, meaning it has a high runoff potential during intense storm events. This requires careful management of surface water to prevent erosion on sloped fields.
Thriving in the Warm Zone 8a
The warm 8a hardiness zone allows for an expansive variety of crops, including berries, peaches, and southern peas. The clay loam provides a sturdy anchor for fruit trees and large perennials. Your garden will thrive here with regular organic additions to improve the soil's natural tilth.
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
Moderately well drained
Water is removed somewhat slowly. May have a slowly permeable layer or seasonal water table.
Soil Profile
Dominant texture: Clay loam
Typical soil profile. Actual depths vary by location.
USDA Soil Orders
Frequently Asked Questions
What type of soil does Johnston County have?
Johnston County's soil is classified as Clay loam. This indicates the relative proportions of sand, silt, and clay — 42% sand, 31% silt, and 23% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Johnston County's soil acidic or alkaline?
Johnston 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 Johnston County?
Johnston 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 Johnston County's soil?
Based on Johnston County's Clay loam texture, pH of 6.2, 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 Johnston County?
Johnston County's dominant soil order is Alfisols. Alfisols are moderate to high base-status soils with a clay-enriched subsoil. They support productive forests and cropland across temperate regions.
Planning your lawn? View lawn care data for Johnston County on LawnByCounty.com →
Other Counties in Oklahoma
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.