Karnes County Soil Data
Karnes County, Texas
USDA SSURGO / PHZMAvg pH
7.3
Texture
Clay Loam
Drainage
N/A
Organic Matter
1.8%
Hydrologic Group
D
Data Story
About Soil in Karnes County, Texas
Highly Alkaline South Texas Soils
Karnes County features an average pH of 7.32, making it significantly more alkaline than the national median of 6.5. This soil score of 31.1 is healthy, outperforming the state average of 28.8. Many local plants have adapted specifically to these higher lime levels.
Sandy Loam with High Clay Content
The soil consists of 44.6% sand, 22.0% silt, and 28.1% clay. This high clay percentage gives the soil excellent nutrient retention but can make it heavy and sticky when wet. You will need to wait for the right moisture levels before tilling to avoid clumping.
Rich Organic Matter for Texas
Organic matter averages 1.78%, which is notably higher than the state average of 1.66%. The available water capacity is 0.133 in/in, exactly matching the Texas state average. This combination provides a solid, fertile foundation for productive farming and gardening.
Infiltration Challenges in Group D
Classified in hydrologic group D, these soils have very slow infiltration rates when saturated. This means that during heavy Texas rains, the soil may struggle to absorb water quickly, leading to runoff. Consider using swales or rain gardens to manage water effectively on your property.
Abundant Growth in Zone 9a
Karnes County is in Hardiness Zone 9a, supporting a long growing season for heat-loving plants. You can grow exceptional peppers, melons, and southern peas in this warm environment. Start a garden today and enjoy the benefits of some of the region's most fertile soil.
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
Drainage class data not available.
Soil Profile
Dominant texture: 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 Karnes County have?
Karnes County's soil is classified as Clay Loam. This indicates the relative proportions of sand, silt, and clay — 45% sand, 22% silt, and 28% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Karnes County's soil acidic or alkaline?
Karnes County's soil has a pH of 7.3, which is near neutral. This range is ideal for most garden plants and field crops.
What is the drainage class for Karnes County?
Drainage class data is not currently available for Karnes County.
What crops or plants grow well in Karnes County's soil?
Based on Karnes County's Clay Loam texture, pH of 7.3, and drainage class, the soil is well suited for drought-tolerant crops and native grasses, row crops and vegetable gardens.
What USDA soil order is found in Karnes County?
The dominant USDA soil order for Karnes County is not currently available in our dataset.
Soil & Planting Advisory: Karnes County
Soil Verdict
Karnes County is in USDA hardiness zone 9a, a warm climate zone. where winter lows can reach 20°F. Warm winters keep soil biology active nearly year-round, accelerating decomposition but increasing pest and disease pressure in topsoil.
Planting Guidance
Tropical and subtropical plants are viable. Year-round gardening is possible, though summer heat may limit some cool-season crops. Frost is rare; tender plants can overwinter with minimal 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
Rapid organic matter turnover means soils can become nutrient-poor quickly; test annually and fertilize based on results. High soil temperatures favor certain soilborne pathogens; practice crop rotation and avoid overwatering.
Regional Context
Karnes County is somewhat warmer than the Texas statewide average.
Planning your lawn? View lawn care data for Karnes County on LawnByCounty.com →
Other Counties in Texas
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.