Reference soil United States of America 12: Regosol

US012

Regosols are found in areas where soil has been eroded to the extent that the underlying unconsolidated materials come near to the surface, or where soil formation has not played an important role, e.g. in desert regions. The name comes from the greek 'rhegos' :blanket meaning young soils on weathering materials.

Characteristics

Soils in medium and fine textured materials, having no distinctive horizons other than an ochric horizon at the surface.

Distribution of Regosols (rough estimation supplied by soilgrids)

Reference soil US012: Regosols

Classification

WRB 1998

Calcaric- Regosol

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Calcaric Regosol

Local classification:	Yolo silt loam

Other classification

USDA-NRCS (1999)	Typic Xerorthent
USDA-SCS (1975)	Typic Xerorthent xeric fine-silty mixed thermic

Physical characteristics

Particle size distribution

Depth (cm)	Gravel % v/v	very coarse sand % w/w	coarse sand % w/w	medium sand % w/w	fine sand % w/w	very fine sand % w/w	Total sand % w/w	coarse silt % w/w	fine silt % w/w	Total silt % w/w	Clay % w/w
0-12	0	0	0.1	0.4	14.5	29.6	44.6	18.3	20.4	38.7	16.7
12-55	0	0	0.1	0.7	1.7	5.3	7.8	31.4	41.5	72.9	19.5
55-70	0	0	0.1	1.1	17.6	27.7	46.5	20.2	18.7	38.9	14.6
70-85	0	0	0.1	1	6.9	14.9	22.9	29.3	29.3	58.6	18.5
85-115	0	0	0	0.1	3.2	14.4	17.7	32.5	29.5	62	20.2
115-130	0	0	0	0.4	6.9	14.2	21.5	22.4	32.4	54.8	23.7

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
0-12	1.33	-	-	-	16.7
12-55	1.38	-	-	-	19.5
55-70	1.27	-	-	-	14.6
70-85	1.21	-	-	-	18.5
85-115	1.2	-	-	-	20.2
115-130	1.16	-	-	-	23.7

Other physical data

Depth (cm)	Bulk density kg/dm³	pF 0 % v/v	pF 1.0 % v/v	pF 1.5 % v/v	pF 2.0 % v/v	pF 2.3 % v/v	pF 2.7 % v/v	pF 3.4 % v/v	pF 4.2 % v/v
0-12	1.33	-	-	-	-	-	-	-	13.1
12-55	1.38	-	-	-	-	-	-	-	13.9
55-70	1.27	-	-	-	-	-	-	-	13.2
70-85	1.21	-	-	-	-	-	-	-	12.1
85-115	1.2	-	-	-	-	-	-	-	11.1
115-130	1.16	-	-	-	-	-	-	-	12.8

Chemical data

Depth (cm)	pH H2O	pHKCl	EC 1: 2.5 dS/m	CaCO3 % w/w	C % w/w	N %	C / N	Exch. Acid cmol(c)/kg	Exch. Al cmol(c)/kg	Ca cmol(c)/kg	Mg cmol(c)/kg	K cmol(c)/kg	Na cmol(c)/kg	Sum Cations cmol(c)/kg
0-12	7.4	6.2	0.11	2.1	0.40	0.04	10	-	-	9.7	12.4	0.2	0.5	22.8
12-55	7.4	6.3	0.13	2.6	0.59	0.06	10	-	-	13.4	14.7	0.2	0.4	28.7
55-70	7.7	6.3	0.08	2.3	0.33	0.05	7	-	-	8.8	11.6	0.2	0.4	21
70-85	7.6	6.2	0.07	2.7	0.56	0.06	9	-	-	10.2	13.7	0.2	0.4	24.5
85-115	7.6	6.0	0.09	2.4	0.63	0.07	9	-	-	10.4	14.1	0.3	0.4	25.2
115-130	7.4	5.9	0.1	2.9	1.00	0.10	10	-	-	11.2	14.3	0.4	0.2	26.1

Depth (cm)	Base sat. %	CEC soil cmol(c)/kg	CEC clay cmol(c)/kg	CEC org cmol(c)/kg	ECEC cmol(c)/kg	Al sat. %	ESP %
0-12	101	22.5	135	1.4	-	-	2
12-55	106	27.0	138	2.1	-	-	1
55-70	104	20.2	138	1.2	-	-	2
70-85	102	24.1	130	2.0	-	-	2
85-115	100	25.2	125	2.2	-	-	2
115-130	98	26.7	113	3.5	-	-	1

Depth (cm)	pH NaF	P Retention %	ODOE	Al o % w/w	Si o % w/w	Fe d % w/w	Al d % w/w	Fe p % w/w	Al p % w/w	C p % w/w	Fe o % w/w
0-12	-	-	-	-	-	1.7	0.2	-	-	-	-
12-55	-	-	-	-	-	1.7	0.2	-	-	-	-
55-70	-	-	-	-	-	1.7	0.2	-	-	-	-
70-85	-	-	-	-	-	1.7	0.1	-	-	-	-
85-115	-	-	-	-	-	1.7	0.2	-	-	-	-
115-130	-	-	-	-	-	1.7	0.2	-	-	-	-

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
55-70	-	-	-	-	-	-	weak to medium	very weak to weak	-	very weak	weak to medium	very weak to weak
85-115	-	-	-	-	-	-	weak to medium	very weak to weak	-	very weak	weak to medium	very weak to weak

Soluble sands

Depth (cm)	Ca mmol(c)/kg	Mg mmol(c)/kg	K mmol(c)/kg	Na mmol(c)/kg	sum cations mmol(c)/kg	CO3 mmol(c)/kg	HCO3 mmol(c)/kg	Cl mmol(c)/kg	NO3 mmol(c)/kg	SO4 mmol(c)/kg	sum anions mmol(c)/kg
0-12	2	3.9	0.3	0.7	6.9	0	4.5	0.8	0.2	1.0	6.5
12-55	1.1	2	0.1	0.6	3.8	0	1.5	0.2	1.1	0.5	3.3
55-70	0.8	1.4	0.1	0.6	2.9	0	1.2	0.2	1.0	0.3	2.7
70-85	0.6	1.0	0.1	0.6	2.3	0	1.2	0.2	0.6	0.3	2.3
85-115	0.8	1.4	0.1	0.7	3	0	1.8	0.1	0.7	0.2	2.8
115-130	1.1	1.6	0.1	0.9	3.7	0	2.5	0.2	0.7	0.3	3.7

Depth (cm)	Sodium ads. ratio	pH e	EC e dS/m	EC 1 : 5 dS/m
0-12	0.41	7.1	0.64	-
12-55	0.48	7.1	0.39	-
55-70	0.57	7.2	0.3	-
70-85	0.67	7.4	0.23	-
85-115	0.67	7.8	0.29	-
115-130	0.77	8	0.35	-

Profile description

Ap1 0-12 cm	greyish brown (2.5Y 5/2, dry) very dark greyish brown (10YR 3/2, moist)sandy loam,very hard friable slightly sticky slightly plastic,many very fine interstitial pores and many tubular pores,few very fine roots,abrupt broken boundary to,
Ap2 12-55 cm	greyish brown (2.5Y 5/2, dry) dark brown (10YR 3/3, moist)sandy loam,massive,hard friable slightly sticky slightly plastic,common very fine tubular pores,few very fine roots,clear smooth boundary to,
AC 55-70 cm	greyish brown (2.5Y 5/2, dry) very dark greyish brown (10YR 3/2, moist)silty clay loam,massive,slightly hard friable slightly sticky plastic,many very fine tubular pores,few very fine roots,clear wavy boundary to,
C1 70-85 cm	brown (10YR 5/3, dry) olive brown (2.5Y 4/4, moist)sandy loam,massive,slightly hard friable slightly sticky slightly plastic,few very fine tubular pores,few very fine roots,clear wavy boundary to,
C2 85-115 cm	pale brown (10YR 6/3, dry) olive brown (2.5Y 4/4, moist)very fine sandy loam,massive,soft very friable non sticky non plastic,few very fine roots,clear smooth boundary to,
Ahb 115-130 cm	greyish brown (2.5Y 5/2, dry) very dark greyish brown (2.5Y 3/2, moist)sandy loam,massive,slightly hard friable slightly sticky slightly plastic,few very fine roots,

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Reference soil United States of America 12: Regosol

Characteristics

Reference soil US012: Regosols

Classification