LOCATION NEBGEN                  TX

Established Series


The Nebgen series consists of very shallow or shallow, well drained soils formed in residuum from Cambrian age sandstone bedrock. These soils occur on backslopes, shoulders and summits of ridges. Slopes range from 1 to 30 percent. Mean annual air temperature is about 19 degrees C (66 degrees F), and mean annual precipitation is about 787 mm (31 in).

TAXONOMIC CLASS: Loamy, mixed, active, nonacid, thermic Lithic Ustorthents

TYPICAL PEDON: Nebgen sandy loam--in rangeland.
The surface is covered by about 20 percent sandstone cobbles.
(Colors are for dry soil unless otherwise stated).

A1--0 to 13 cm (0 to 5 in); brown (7.5YR 4/4) sandy loam, dark brown (7.5YR 3/4) moist; moderate medium granular structure; slightly hard, friable; common fine roots; 5 percent, 2 to 75 mm, sandstone; slightly acid; clear smooth boundary.

A2--13 to 28 cm (5 to 11 in); brown (7.5YR 4/4) sandy loam, dark brown (7.5YR 3/4) moist; moderate medium granular structure; slightly hard, friable; common fine roots; 10 percent, 2 to 75 mm, sandstone; slightly acid; abrupt smooth boundary. (Combined thickness of the A horizon is 10 to 36 cm [4 to 14 in])

R--28 to 53 cm (11 to 21 in); reddish brown indurated sandstone bedrock.

TYPE LOCATION: Llano, County, Texas; From the intersection of Highway 16 and Ranch Road 2323, 16.3 miles southwest on Ranch Road 2323, 0.2 mile on east county Road, and 500 feet south west in rangeland.
USGS topographic quadrangle: Enchanted Rock, Texas;
Latitude: 30 degrees, 35 minutes, 1.3 seconds N;
Longitude: 98 degrees, 51 minutes, 31.2 seconds W;
Datum: NAD83

Soil moisture: Typic ustic moisture regime
Solum thickness: 10 to 36 cm (4 to 14 in) to sandstone bedrock
Surface Fragments: 1 to 25 percent by area, sandstone, cobbles and stones

A horizon
Hue: 2.5YR to 10YR
Value: 3 to 6
Chroma: 3 to 6
Texture: loamy sand, sandy loam, fine sandy loam, or their gravelly counterparts
Rock fragments: 0 to 25 percent; sandstone gravel or cobbles
Base saturation: More than 75 percent
Other features: In pedons where moist value and chroma are 3 or less, the epipedon is not thick enough for a mollic epipedon.
Reaction (pH): Moderately acid to neutral (5.6 - 7.3)

R layer
Red or brown sandstone, that has near horizontal bedding planes and is strongly cemented or indurated. The sandstone or individual strata within the sandstone are calcareous in some pedons.

COMPETING SERIES: There are no series in the same family. Similar soils are the Darnell, Latom, Loving, and Yates series.
Darnell soils: Have a cambic horizon.
Latom soils: Are calcareous and dry in the moisture control section for longer periods.
Loving soils: Have a paralithic contact to Pennsylvanian age sandstone.
Yates soils: Have a loamy-skeletal particle-size control section over limestone.

Parent material: The soil formed in strongly cemented or indurated sandstone bedrock mostly of the Hickory Formation but with some formed in Lion Mountain and Cap Mountain Formations of Cambrian age.
Landscape: Dissected plateau
Landform: Backslopes, shoulders and summits of ridges
Slopes: 1 to 30 percent
Precipitation Pattern: The majority of the yearly amount occurs during the fall and spring months. The winter and summer months are normally drier.
Mean annual precipitation: 660 to 838 mm (26 to 33 in)
Thornthwaite annual P-E index: 37 to 46
Mean annual air temperature: 17.8 to 20.0 degrees C (64 to 68 degrees F)
Frost-free period: 215 to 235 days
Elevation: 304.8 to 671 m (1,000 to 2,200 ft)

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Campair, Eckert, Hye, Loneoak, Matilo, Oben, Pontotoc, and Yates series.
Campair, Hye, Loneoak, Matilo, Oben, and Pontotoc soils: Have argillic horizons
Campair, Hye, Loneoak, Matilo, and Pontotoc soils: Are more than 50 cm (20 in) thick over sandstone bedrock
Campair, Loneoak, and Matilo soils: Have sandy surface layers.
Eckert and Yates soils: Have a loamy-skeletal particle-size control section over limestone. In addition, Eckert soils have a mollic epipedon.

DRAINAGE AND PERMEABILITY: These soils are well drained. Permeability is moderately rapid in the soil and moderate to moderately slow in the sandstone bedrock. Runoff is low on 1 to 5 percent slopes, medium on 5 to 20 percent slopes, and high on 20 to 30 percent slopes.

USE AND VEGETATION: Used for rangeland. Native vegetation includes sand lovegrass, hooded windmillgrass, threeawns, and little bluestem. Woody vegetation consists of persimmon, live oak, post oak, blackjack oak, whitebrush, and catclaw.

DISTRIBUTION AND EXTENT: Central Texas; Southwest Plateaus and Plains Range and Cotton Region, LRR-I: MLRA 82A-Texas Central Basin. This series is of moderate extent.


SERIES ESTABLISHED: Gillespie County, Texas; 1970.

The soil classifies in the active cation exchange activity class.

Edited 09/2016 (RFG-THW): Changed to tabular format. Added metric measurements. Updated competing series, geographic setting, and associated soils sections.

Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: 0 to 28 cm (0 to 11 in). (A horizons)
Lithic contact: Indurated sandstone bedrock at 28 cm (11 in). (top of R layer)


Taxonomic Version: Keys to Soil Taxonomy, 12th Edition, 2014.

National Cooperative Soil Survey