LOCATION KNIPPA                  TX

Established Series
Rev. EHT-HCD-WJG
10/2016

KNIPPA SERIES

The Knippa series consists of very deep, well drained, moderately slowly permeable soils that formed in calcareous clayey alluvium derived from limestone. The soils are on nearly level to gently sloping stream terraces of piedmont alluvial plains below limestone hills. Slopes range from 0 to 3 percent. Mean annual precipitation is about 686 mm (27 in), and mean annual air temperature is about 20.6 degrees C (69 degrees F).

TAXONOMIC CLASS: Fine, mixed, superactive, thermic Vertic Calciustolls

TYPICAL PEDON: Knippa clay - cropland.
(Colors are for dry soil unless otherwise stated)

Ap--0 to 20 cm (0 to 8 in); dark grayish brown (10YR 4/2) clay, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure; very hard, firm but crumbly; many fine roots; upper 1 inch is loose flattened granules; few fine strongly cemented calcium carbonate concretions to 1 mm; violently effervescent; moderately alkaline; abrupt smooth boundary.

A--20 to 46 cm (8 to 18 in); brown (7.5YR 4/2) clay, dark brown (7.5YR 3/2) moist; moderate fine and very fine angular blocky structure; extremely hard, very firm; many fine roots; few fine pores and old root channels; shiny pressure faces on peds; few strongly cemented calcium carbonate concretions to 3 mm; few worm casts; organic staining on few peds; violently effervescent; moderately alkaline; gradual wavy boundary. Combined thickness of the A horizon is 25 to 56 cm (10 to 22 in)

Bw--46 to 71 cm (18 to 28 in); reddish brown (5YR 4/3) clay, dark reddish brown (5YR 3/3) moist; moderate fine and very fine angular blocky structure; extremely hard, very firm; few fine roots and old root channels; few fine pores; few worm casts; shiny pressure faces on peds; few strongly cemented calcium carbonate concretions to 3 mm; organic staining on few peds; violently effervescent; moderately alkaline; gradual wavy boundary. Thickness of the Bw horizon is 20 to 71 cm (8 to 28 in)

Bk1--71 to 89 cm (28 to 35 in); brown (7.5YR 4/4) clay, brown (7.5YR 4/4) moist; moderate fine angular blocky structure; extremely hard, very firm; very few roots; few old root channels and fine pores; contains an estimated 5 percent by volume of strongly cemented calcium carbonate concretions; violently effervescent; moderately alkaline; gradual wavy boundary. Thickness of the Bk1 horizon is 0 to 38 cm (0 to 15 in)

Bk2--89 to 122 cm (35 to 48 in); light brown (7.5YR 6/4) silty clay loam, brown (7.5YR 5/4) moist; weak fine subangular blocky structure; hard, friable; contains an estimated 30 percent by volume of cemented concretions and soft masses of calcium carbonate; violently effervescent; moderately alkaline; diffuse wavy boundary. Thickness of the Bk2 horizon is 15 to 76 cm (6 to 30 in)

Bk3--122 to 152 cm (48 to 62 in); pink (7.5YR 7/4) silty clay loam, reddish yellow (7.5YR 6/6) moist; weak fine subangular blocky structure; hard, friable; contains an estimated 20 percent by volume of soft masses and cemented concretions of calcium carbonate; violently effervescent; moderately alkaline.

TYPE LOCATION: Uvalde County, Texas; from the intersection of US Highway 83 and US Highway 90 in Uvalde, Texas, about 15 miles east on US Highway 90, about 370 feet north on County Road 343, and 300 feet west (about 3.9 miles east of Knippa, Texas, on U.S. Highway 90, 0.1 mile north across railroad track) in cultivated field.
USGS topographic quadrangle: Blanco Lake, TX;
Latitude: 29 degrees, 18 minutes, 56.48 seconds N;
Longitude: 99 degrees, 34 minutes, 37.15 seconds W;
Datum: WGS84.
UTM Easting 443972.70 m, UTM Northing 3243100.25 m, UTM Zone 14.

RANGE IN CHARACTERISTICS:
Soil Moisture: Mostly Typic-Ustic soil moisture regime, but does occur in the Aridic-Ustic.
Depth to secondary calcium carbonate: 45 to 100 cm (18 to 40 in)
Depth to calcic horizon: 45 to 100 cm (18 to 40 in)
Thickness of the mollic epipedon: 45 to 100 cm (18 to 40 in)
Vertic features: 10 to 100 cm (4 to 40 in)

Particle-size control section (weighted average)
Total clay content: 40 to 55 percent
Carbonate Clay content: 2 to 15 percent
Rock fragments: 0 to 6 percent

A Horizon
Hue: 5YR to 10YR
Value: 3 to 5
Chroma: 1 to 3
Texture: clay or silty clay
Total clay content: 40 to 55 percent
Rock fragments: 0 to 6 percent; gravels; limestone
Calcium carbonate equivalent: 10 to 30 percent
Electrical conductivity (mmhos/cm): 0 to 2
Effervescence: strong to violent
Reaction (pH): slightly alkaline to moderately alkaline (7.4 to 8.4)

Bw Horizon
Hue: 5YR to 10YR
Value: 3 to 5
Chroma: 2 to 4
Texture: clay or silty clay
Total clay content: 40 to 55 percent
Rock fragments: 0 to 6 percent; gravels; limestone
Identifiable secondary carbonates: 0 to 2 percent, by volume; concretions or nodules
Calcium carbonate equivalent: 10 to 40 percent
Electrical conductivity (mmhos/cm): 0 to 2
Effervescence: violent
Reaction (pH): slightly alkaline to moderately alkaline (7.4 to 8.4)

Bk1 Horizon
Hue: 5YR to 10YR
Value: 3 to 5
Chroma: 4 to 6
Texture: clay or silty clay
Total clay content: 40 to 55 percent
Rock fragments: 0 to 10 percent; gravels; limestone
Identifiable secondary carbonates: 3 to 10 percent, by volume; concretions, nodules, or soft masses
Calcium carbonate equivalent: 15 to 50 percent
Electrical conductivity (mmhos/cm): 0 to 2
Effervescence: violent
Reaction (pH): slightly alkaline to moderately alkaline (7.4 to 8.4)

Bk2 and Bk3 Horizon
Hue: 5YR to 10YR
Value: 6 or 8
Chroma: 4 to 6
Texture: silty clay loam, clay loam, clay or silty clay
Total clay content: 30 to 50 percent
Rock fragments: 0 to 20 percent; gravels; limestone
Identifiable secondary carbonates: 10 to 40 percent, by volume; concretions, nodules, or soft masses
Calcium carbonate equivalent: 30 to 70 percent
Electrical conductivity (mmhos/cm): 0 to 2
Effervescence: violent
Reaction (pH): slightly alkaline to moderately alkaline (7.4 to 8.4)

COMPETING SERIES: These are the Chatt and Rowena series in the same family. Similar soils are the Uvalde, Olmito and Raymondville series.
Chatt soils: occur in areas of higher rainfall and are moist in the moisture control section for longer periods.
Rowena soils: occur in areas where the mean air temperature is less than 68 degrees F.
Olmito soils: occur in areas where the mean air temperature is greater than 72 degrees F and has a smectitic mineralogy class.
Raymondville soils: occur in areas where the mean air temperature is greater than 72 degrees F.Uvalde soils: have a fine-silty particle-size control section

GEOGRAPHIC SETTING:
Parent material: calcareous clayey alluvium derived from limestone
Landscape: inland, dissected coastal plains
Landform: stream terraces on piedmont alluvial plains below limestone hills
Slope: 0 to 3 percent
Mean annual precipitation: 584 to 838 mm (23 to 33 in)
Thornthwaite P-E Index: 28 to 44
Mean annual air temperature: 20.0 to 21.1 degrees C (68 to 70 degrees F)
Frost-free period: 240 to 270 days
Elevation: 213.4 to 670.6 m (700 to 2200 ft)

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Castroville, Montell, Olmos, Rehm, Sabenyo, Uvalde, and Valco soils.
Castroville soils: have a fine-silty particle-size control section and carbonatic mineralogy.
Montell soils: are clayey throughout and have intersecting slickensides at depths of less than 40 inches.
Olmos and Valco soils: occur on low ridges and are shallow to a petrocalcic horizon.
Rehm soils: have a loamy-skeletal particle-size control section.
Sabenyo soils: occur on lower terrace risers and have a fine-loamy particle-size control section.
Uvalde soils: occur on similar positions and have a fine-silty particle-size control section.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderately slow. The runoff is low on slopes of 0 to 1 percent and medium on slopes of 1 to 3 percent.

USE AND VEGETATION: The soil is used for rangeland and cropland, both dryland and irrigated. Under dryland operations, grain sorghums, small grains and introduced grasses are the principal crops. Under irrigation, grain sorghums, small grain and a variety of winter truck crops are grown. The present native grasses are red grama, threeawn, curlymesquite, bristlegrass, Hall's panicum, fall witchgrass and sideoats grama. Woody vegetation includes mesquite, whitebrush, Texas persimmon, twisted acacia, catclaw acacia, Texas colubrina, lotebush and bluewood condalia.

DISTRIBUTION AND EXTENT: Northern and Western Rio Grande Plain MLRAs (83A and 83B) and Eastern Edwards Plateau MLRA (81C) of Texas. The series is of moderate extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas

SERIES ESTABLISHED: Uvalde County, Texas; 1966.

REMARKS:

Edited 10/2016 (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:
Particle size control section: 25 to 100 cm (10 to 40 in.) (A, Bw, and Bk1 horizons)
Mollic epipedon - 0 to 71 cm (0 to 28 in) (A and Bw horizons)
Calcic horizon - 71 to 152 cm (28 to 62 in) (Bk horizons)

ADDITIONAL DATA: KSSL Data from pedons S1963TX463001 and S1963TX463002.

Taxonomic Version: Keys to Soil Taxonomy, Twelve Edition, 2014

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National Cooperative Soil Survey
U.S.A.