Castro County Soil Data
Castro County, Texas
USDA SSURGO / PHZMAvg pH
7.7
Texture
Clay Loam
Drainage
N/A
Organic Matter
2.2%
Hydrologic Group
D
Data Story
About Soil in Castro County, Texas
Highly Alkaline High Plains Soil
Castro County's soil is notably alkaline with an average pH of 7.73, well above the national median of 6.5. This pH level is higher than the state average of 7.09, which can impact the availability of micronutrients like iron. Proper management is key for local farmers to keep crops healthy in these conditions.
Heavy Soil with Clay Influence
The soil contains 29.0% clay and 32.5% silt, giving it more body than many other Texas counties. This 38.5% sand mix provides enough structure for agricultural workability while the clay helps store essential nutrients. It is a dense, productive mix typical of the productive High Plains region.
Rich in Organic Matter
At 2.24%, Castro County's organic matter exceeds both the state average of 1.66% and the national average of 2.0%. Combined with an impressive water capacity of 0.157 in/in, these soils are built for high productivity. This fertile foundation makes it one of the more robust agricultural areas in the state.
Slow Drainage and High Runoff
Belonging to hydrologic group D, these soils have a very slow infiltration rate when saturated. This means that during heavy rains, water is more likely to run off the surface than soak in deeply. Producers must manage irrigation carefully to prevent standing water and ensure the ground absorbs moisture effectively.
Thriving in Hardiness Zone 7a
With a USDA Hardiness Zone of 7a, Castro County is ideal for a variety of hardy crops and regional staples. The high water capacity supports the growth of corn, cotton, and wheat under irrigation. Gardeners should prioritize plants that tolerate alkaline conditions and enjoy the long, sunny days.
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
Alkaline Soil Detected
Your county's average pH is 7.7. These products help acidify soil for better nutrient uptake.
Browse Soil AmendmentsFrequently Asked Questions
What type of soil does Castro County have?
Castro County's soil is classified as Clay Loam. This indicates the relative proportions of sand, silt, and clay — 39% sand, 32% silt, and 29% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Castro County's soil acidic or alkaline?
Castro County's soil has a pH of 7.7, which is mildly to moderately alkaline. Sulfur amendments can lower pH if needed.
What is the drainage class for Castro County?
Drainage class data is not currently available for Castro County.
What crops or plants grow well in Castro County's soil?
Based on Castro County's Clay Loam texture, pH of 7.7, 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 Castro County?
The dominant USDA soil order for Castro County is not currently available in our dataset.
Soil & Planting Advisory: Castro County
Soil Verdict
Castro County is in USDA hardiness zone 7a, a moderate climate zone. where winter lows can reach 0°F. Mild winters mean soil rarely freezes deeply, allowing year-round microbial activity and faster organic matter breakdown.
Planting Guidance
Warm-season crops, citrus relatives, and heat-loving ornamentals do well. Cool-season vegetables should be planted in fall and winter. 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
Warm soils accelerate organic matter breakdown, so compost and mulch need replenishing more frequently than in cooler zones. Sandy soils common in warm zones drain quickly; water-retentive amendments like compost or peat help hold moisture. When soil temperatures drop below freezing, microbial nitrogen cycling stops; spring fertilization is more effective than late-fall application.
Regional Context
Castro County is somewhat cooler than the Texas statewide average.
Planning your lawn? View lawn care data for Castro 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.