Reference soil Ecuador 07: Acrisol

EC007

Acrisols occur dominantly in the wetter parts of the tropics and subtropics and the warm temperate regions in relatively young landscapes.

Characteristics

Soils having an argic horizon (a subsurface horizon with distinct higher clay content than the overlying horizon), which has a cation exchange capacity of less than 24 cmolc per kg in some part, either starting within 100 cm from the soil surface, or within 200 cm from the soil surface if the argic horizon is overlain by loamy sand or coarser textures throughout. They have a base saturation (total amount of Ca, Mg, K and Na with respect to the cation exchange capacity) of less than 50 percent in the major part between 25 and 100 cm from the soil surface

Distribution of Acrisols (rough estimation supplied by soilgrids)

Reference soil EC007: Acrisols

Brief description of the soil: deep, well drained, yellowish brown clay. At about 90 cm starts a hard cemented sandy tuff substratum. The parent material consists of two layers. From 0 to 92cm quarternary alluvium, probably mixed with some volcanic ash. From 92cm starts abruptly a very hard layer, consisting of sandy ash, probably transported and deposited by the river. The genesis of the cementation and hardness of this layer is not yet understood. The very hard layer could only be broken with a pick-axe. The hard layer blocks root development and permeability for water is low. No water table has been observed, however it is assumed that excess water runs laterally to depressions. * INIAP station San Carlos trial field has about 350 cocoa varieties. FAO, 1988 Haplic Acrisol USDA, 1990 ?

Classification

WRB 2006

WRB 1998

Vitric-Endoleptic-Cutanic- Acrisol (Ruptic Alumic Humic)

Vitri-Endoleptic- Acrisol (Humic Alumic)

8-92 cm	argic horizon
-	lithological discontinuity

0-38 cm	ochric horizon
8-92 cm	argic horizon
-	strongly humic

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Humi-Haplic Acrisol

Ferric Acrisol

0-38 cm	ochric A horizon
8-92 cm	argic B horizon
-	strongly humic

0-38 cm	ochric A horizon
8-92 cm	argillic B horizon
-	ferric

Local classification:	Suelo aluvial

Other classification

USDA-SCS (1975)

Tropaquult perudic clayey isohyperthermic

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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
0-8	0	1.6	2.7	2.6	3.7	3.4	14.0	10.3	22.9	33.2	52.9
8-38	0	1.2	1.8	1.7	2.5	2.5	9.7	6.5	22.3	28.8	61.6
38-92	0	0.6	0.9	0.9	1.3	1.2	4.9	3.7	11.7	15.4	79.7
92-150	0	6.0	14.0	17.3	21.7	7.3	66.3	0.8	15.9	16.7	16.9

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
15-20	0.910	-	-	-	-
0-8	-	-	-	2.6	52.9
40-60	0.900	-	-	-	-
8-38	-	-	-	2.6	61.6
38-92	-	-	-	0.0	79.7
92-150	-	-	-	0.0	16.9

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
15-20	0.910	61.5	61.0	54.9	51.7	50.3	48.8	27.3	25.0
40-60	0.900	67.0	65.7	59.0	55.8	54.5	52.9	34.2	32.0

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
0-8	4.6	4.0	0.30	-	3.20	0.37	9	2.2	1.9	3.2	1.3	0.3	0.0	4.8
8-38	4.8	3.9	0.08	-	1.29	0.14	9	3.4	3.3	1.5	0.7	0.2	0.0	2.4
38-92	5.2	3.7	0.02	-	0.39	0.04	10	6.5	6.4	1.3	0.9	0.1	0.3	2.6
92-150	5.8	4.6	0.01	-	0.14	0.01	14	0.5	0.5	0.6	0.3	0.1	0.2	1.2

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 %
0-8	31	15.6	29	11.2	-	12	0
8-38	19	12.8	21	4.6	-	26	0
38-92	16	16.3	20	1.4	-	39	2
92-150	13	9.5	56	0.4	-	5	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
0-8	8.4	72	-	0.70	0.10	3.40	0.90	0.70	0.30	-	0.80
8-38	8.9	73	-	0.60	0.10	4.60	0.90	0.40	0.20	-	0.80
38-92	9.2	81	-	0.60	0.10	4.30	0.90	0.20	0.20	-	0.60
92-150	10.0	93	-	4.10	2.30	1.60	0.40	0.00	0.20	-	0.20

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-8	-	weak	medium to strong	-	medium to strong	-	-	-	-	-	weak	-
8-38	-	weak	medium to strong	-	medium to strong	-	-	-	-	-	weak	-
38-92	-	weak	medium to strong	-	medium to strong	-	-	-	-	-	-	-
92-150	-	weak	weak	-	medium to strong	-	-	-	-	-	-	-

Profile description

Ah 0-8 cm	dark yellowish brown (10YR 3/6, moist)clay,moderate very fine crumb and moderate very fine granular,friable sticky plastic,many very fine fine interstitial pores,gradual smooth boundary to,
8-38 cm	dark yellowish brown (10YR 3/6, moist)clay,moderate fine and medium subangular blocky,friable sticky plastic,many very fine fine continuous inped tubular random pores,gradual smooth boundary to,
Bt 38-92 cm	dark yellowish brown (10YR 4/6, moist)clay,moderate medium subangular blocky,friable sticky plastic,broken moderately thick clay on pedfaces cutans,few very fine fine continuous inped tubular random pores,very few medium gravel fresh C hor. fragment fragments,abrupt wavy boundary to,
2Cm 92-150 cm	(dark) brown (10YR 4/3, moist)strongly coherent porous massive,very firm non sticky non plastic,few very fine continuous inped tubular random pores and common fine interstitial pores,

Depth1	92cm
Kind 1 (parent material) ; Parker (eds), 1984	sediment, unconsolidated
Kind 2 (parent material) (second entry); Parker (eds), 1984	pyroclastic, unconsolidated
Mode of accumulation or deposition of parent material	fluvial
Mode of accumulation or deposition of parent material (second entry)	fluvial
Soil Depth	92cm
Texture of parent material	clayey
Texture of parent material (second entry)	sandy
Weathering Resistance	poor
Weathering Resistance (second entry)	poor
General characterization of the status of weathering of solid rock	slightly
General characterization of the status of weathering of solid rock (second entry)	slightly

Major crops	cocoa
Land use or vegetation in the immediate vicinity of the site	tree and shrub cropping
Remarks on Land Use / Vegetation	VEGETATION: LANDUSE: INIAP experimental station nearby
Status of vegetation; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	primary
Major vegetation type; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	evergreen forest

Altitude	260m
Physiographic Unit	high terrace
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 terrace
Slope	0%
Form of the slope surrounding the site	straight
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	flat or almost flat

Lower limit of a slow permeable or stagnating layer in the profile	150cm
Drainage class ; FAO (2006) - Guidelines for soil description	well
Flooding frequency (FAO, 1986)	never
Kind of ground water table (USDA, 1979)	no groundwater table observed
Moist From - To	0-150cm
Estimated permeability (class) of least permeable part of the profile	slow
Estimated run off (class)	very slow
Upper limit of a slow permeable or stagnating layer in the profile	92cm

Evidence of alkali ; Soil Survey Manual USDA, 1951	non-alkaline
Surface cracking	no cracks observed
Slaking of aggregates by tillage, rainfall or frost (USDA/SCS, 1979)	no surface slaking/crusting 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 Ecuador 07: Acrisol

Characteristics

Reference soil EC007: Acrisols

Classification