Reference soil Uruguay 04: Regosol

UY004

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 UY004: Regosols

DRAINAGE PATTERN: coarse dendrite DOMINANT SPECIES: trachypogon montufari, paspalum notatum, andropogon ternatus, richardia humistrata, cyperus spp., axonopus affinis, axonopus argentinus spp. MORPHOLOGY: C Weathered rock, banded with alterated black minerals on the surface of which clay (10YR6/3) is found (unlcear whether the clay is formed in situ or illuviated). Probably biotite is alterated to vermiculite. Colours (dry) also 7.5YR5/8 and 10YR7/6

Classification

WRB 2006

WRB 1998

Epileptic- Regosol (Humic Eutric)

Humi-Epileptic- Regosol (Eutric)

-	continuous rock

0-28 cm	ochric horizon
-	continuous hard rock

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Humi-Dystric Regosol lithic

Dystric Regosol lithic

0-28 cm	ochric A horizon
-	continuous hard rock

0-28 cm

ochric A horizon

Local classification:	Brunosol subéutrico háplico

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
0-20	-	21.1	15.0	11.9	13.1	6.8	67.9	11.4	7.3	18.7	13.4
20-28	-	25.8	16.5	8.3	8.1	5.1	63.8	9.1	6.2	15.3	20.8
28-	-	16.9	23.9	14.9	10.1	5.0	70.8	7.2	8.4	15.6	13.6

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
0-20	1.274	-	-	-	13.4
20-28	-	-	-	-	20.8
28-	-	-	-	-	13.6

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
0-20	1.274	49.3	47.4	41.8	26.9	19.6	17.1	9.5	8.0

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
0-20	5.1	4.0	0.1	-	1.45	0.14	10	0.9	0.4	2.4	0.9	0.3	0.0	3.6
20-28	5.0	4.0	0.07	-	1.08	0.12	9	2.1	1.3	2.0	0.7	0.4	0.2	3.3
28-	5.4	4.0	0.05	-	0.40	0.04	10	0.9	0.4	4.1	1.9	0.2	0.2	6.4

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 %
0-20	55	6.5	49	5.1	-	6	0
20-28	40	8.3	40	3.8	-	16	2
28-	96	6.7	49	1.4	-	6	3

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
0-20	-	-	-	0.08	0.00	0.48	0.10	0.07	0.04	-	0.13
20-28	-	-	-	0.17	0.00	0.65	0.18	0.10	0.11	-	0.11
28-	-	-	-	0.09	0.01	0.91	0.15	0.04	0.03	-	0.05

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-20	-	weak	-	-	-	-	weak to medium	weak	weak	very weak	weak	-
20-28	-	weak	-	-	-	-	weak to medium	weak	weak	very weak	weak	-
28-	-	weak	-	-	-	-	weak to medium	weak	weak	very weak	weak	-

Profile description

Ah 0-20 cm	(10YR 4.5/3, dry) very dark greyish brown (10YR 3/2, moist)loamy sand slightly gravelly,weak very fine subangular blocky,very hard very friable non sticky,many medium pores,frequent Granite frequent FE-Quartzic fragments,gradual irregular boundary to,
AC 20-28 cm	(10YR 3.5/4, moist)loamy sand very gravelly,weakly coherent,very friable slightly sticky,very frequent Fe-Mn oxides frequent Granite fragments,clear irregular boundary to,
AC 20-28 cm	reddish yellow (5YR 6/8, dry)

Depth1	28cm
Kind 1 (parent material) ; Parker (eds), 1984	igneous rock
Mode of accumulation or deposition of parent material	residual material
Soil Depth	28cm
Texture of parent material	loamy
Weathering Resistance	high
General characterization of the status of weathering of solid rock	highly

Land use or vegetation in the immediate vicinity of the site	semi-natural grassland, grazed
Remarks on Land Use / Vegetation	VEGETATION: Dominant species: Trachypogon montufari, Paspalum notatum, Andropogon ternatus, Richardia humistrata, Cyperus spp, Axonopus affinis, Axonopus argentinus spp LANDUSE:

Altitude	130m
Physiographic position of the site	middle slope
Slope	2%
Slope Aspect	east
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	flat or almost flat

Drainage class ; FAO (2006) - Guidelines for soil description	well
Estimated permeability (class) of least permeable part of the profile	moderate

Evidence of alkali ; Soil Survey Manual USDA, 1951	non-alkaline
Surface cracking	no cracks observed
Rock outcrop class (FAO (2006) - Guidelines for soil description)	none
Evidence of salt; Soil Survey Manual USDA, 1951	non-saline
Surface stoniness class (FAO (2006) - Guidelines for soil description)	none

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Reference soil Uruguay 04: Regosol

Characteristics

Reference soil UY004: Regosols

Classification