Reference soil Ecuador 17: Stagnosol

EC017

Stagnosols are often related to Luvisols and occur for the greater part in humid and perhumid temperate regions in West and Central Europe, North America, Australia and Argentina.

Characteristics

Soils having within 50 cm of the soil surface reducing conditions (soil conditions with low redox potential (negative logarithm of the hydrogen potential (rH) and presence of free iron (Fe2+) on freshly broken surfaces) and in 50% of the layer a stagnic colour pattern (strong mottling of soils in such a pattern that peds surfaces are lighter (at least one Munsell value) and paler (at least one chroma) than ped interiors, which are more reddish and brighter (at least one chroma)). The stagnic color pattern develops under temporarily saturation of a perched water table from surface water, long enough to allow reducing conditions to arise. The topsoil can be bleached and concretions can occur in the subsoil. They develop often in slowly permeable, unconsolidated materials of various origins.

Distribution of Stagnosols (rough estimation supplied by soilgrids)

Reference soil EC017: Stagnosols

The soil when dry has cracks with a width of about 1 cm and to a depth of about 30cm.

Classification

WRB 2006

WRB 1998

Haplic- Stagnosol (Calcaric Siltic)

Calcari-Stagnic- Cambisol

28-150 cm	cambic horizon
-	calcaric
-	stagnic colour pattern
-	reducing conditions

0-47 cm	ochric horizon
28-150 cm	cambic horizon
-	calcaric
-	stagnic

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Stagni-Calcaric Cambisol anthraquic

Calcaric Gleysol

0-47 cm	ochric A horizon
28-150 cm	cambic B horizon
-	stagnic

0-47 cm	ochric A horizon
28-150 cm	cambic B horizon
-	hydromorphic

Local classification:	Suelo de Arrozal

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
0-28	0	0.1	0.2	0.4	1.5	5.1	7.3	13.9	43.6	57.5	35.2
28-47	0	0.2	0.2	0.6	2.3	8.0	11.3	17.0	38.2	55.2	33.7
47-150	0	0.0	0.0	0.1	0.2	2.3	2.6	32.6	46.3	78.9	18.5

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
0-28	-	-	-	30.9	35.2
28-47	-	-	-	31.8	33.7
47-150	-	-	-	14.9	18.5

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
0-28	7.2	5.7	0.23	5.4	0.74	0.04	18	-	-	22.0	12.4	0.1	0.6	35.1
28-47	7.2	5.7	0.32	5.8	0.96	0.10	10	-	-	19.7	10.5	0.2	0.4	30.8
47-150	8.2	6.1	0.19	5.3	0.28	0.03	9	-	-	17.6	11.6	0.0	0.6	29.8

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 %
0-28	109	32.1	91	2.5	-	-	2
28-47	100	30.9	92	3.4	-	-	1
47-150	112	26.7	144	1.1	-	-	2

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
0-28	-	-	-	0.10	0.10	1.40	0.10	0.00	0.00	-	0.40
28-47	-	-	-	0.10	0.10	1.30	0.10	0.10	0.00	-	0.50
47-150	-	-	-	0.10	0.10	1.90	0.10	0.00	0.00	-	0.30

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-28	-	weak	-	-	strong	-	-	-	medium to strong	weak	strong	-
28-47	weak	weak	-	-	strong	-	-	-	medium to strong	weak	medium to strong	-
47-150	weak	weak	-	-	strong	-	-	-	medium to strong	weak	medium to strong	-

Profile description

Ap 0-28 cm	dark yellowish brown (10YR 3/4, moist)clay,moderately coherent porous massive,friable sticky plastic,few very fine medium tubular pores,diffuse smooth boundary to,
ABg 28-47 cm	dark olive grey (5Y 3/2, moist)clay,moderately coherent porous massive,friable sticky plastic,common fine distinct clear mottles (2.5 Y 4/4),few coarse fine tubular pores,diffuse smooth boundary to,
Bg 47-150 cm	olive brown (2.5Y 4/4, moist)clay,moderately coherent porous massive and weak medium subangular blocky,sticky plastic,common fine distinct sharp mottles (5 G 4/1) and common medium distinct mottles (5 G 4/1),few very fine fine tubular pores,few small spherical soft manganiferous nodules,

Kind 1 (parent material) ; Parker (eds), 1984	sediment, unconsolidated
Kind 2 (parent material) (second entry); Parker (eds), 1984	mixed lithology
Mode of accumulation or deposition of parent material	fluvial
Remarks on Parent Materials	Guayas river basin
Soil Depth	150cm
Texture of parent material	clayey
Weathering Resistance	moderate
General characterization of the status of weathering of solid rock	slightly

Intensity of the soil erosion type	slight
Soil erosion type	sheet

Major crops	rice
Land improvements ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	levelling
Main type of irrigation; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	seasonally irrigated
Land use or vegetation in the immediate vicinity of the site	high level arable farming
Rotation scheme ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	crop rotation scheme not relevant

Altitude	16m
Physiographic Unit	lower part of river basin
Physiographic position of the site	flat
Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	alluvial plain
Slope	1%
Form of the slope surrounding the site	straight
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	flat or almost flat

Drainage class ; FAO (2006) - Guidelines for soil description	poor
Flooding frequency (FAO, 1986)	yearly
Nature of flood water	fresh
(Estimated) maximum (lower) depth to groundwater table	150cm
Depth to groundwater table	50cm
Kind of ground water table (USDA, 1979)	groundwater table observed
(Estimated) minimum (upper) depth to groundwater table	0cm
Moist From - To	0-50cm
Estimated permeability (class) of least permeable part of the profile	slow
Estimated run off (class)	ponded
Wet From To	50-150cm

Evidence of alkali ; Soil Survey Manual USDA, 1951	non-alkaline
Surface cracking	small cracks (width less than 1 cm, or depth less than 50 cm)
Micro relief type: small-scale differences in relief in the direct vicinity of the site (FAO, 1986)	levees (artificial)
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 Ecuador 17: Stagnosol

Characteristics

Reference soil EC017: Stagnosols

Classification