Reference soil Zimbabwe 08: Acrisol

ZW008

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 ZW008: Acrisols

(1) The natural vegetation has been cleared to accomodate the Trial Block. Outside the perimeter fences, however, stands of relatively undisturbed natural vegetation occurs. (2) Tree and shrub vegetation in the immediate vicinity of the pit, would have been cut back, but the area has never been ploughed and therefore differs from ZW09 and ZW10 profiles. (3) Grasses, arable weeds and herbaceous shrubs dominate the flora. Occasional Syzygium guineense and Bauhinia thonningii trees occur with 30 metres of the pit. Common Aristolochia heppii, Combretum platypetalum, Dilichos kilimandscharicus and Evolvulus alsinoides shrubs were observed. Herbaceous plants included Lactuca inermis, Pentanisia schweinfurthii, Rhychosia procurrens and Trichodesma physaloides. Arable weeds that were observed included Convolvulus sagittatus, Richardia scabra, Schkuhria pinnata, Tagetes minuta, Vernonia glabra and Waltheria indica. The main grasses were Hyperthelia dissoluta, Heteropogon contortus and Sporobolus pyramidalis with others such as Melanis repens, Brachiaria brizantha and Eragrostis patens present to a lesser extent. (4)

Classification

WRB 2006

Haplic- Acrisol (Profondic Clayic)

34-192 cm

argic horizon

34-192 cm

argic horizon

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Orthi-Haplic Acrisol

Orthic Ferralsol

0-34 cm	ochric A horizon
34-192 cm	argic B horizon

0-34 cm	ochric A horizon
34-192 cm	oxic B horizon
-	weatherable minerals

Land use

Major crops	crops (unspecified)
Land improvements ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	land clearing
Main type of irrigation; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	no irrigation
Land use or vegetation in the immediate vicinity of the site	agro-forestry
Remarks on Land Use / Vegetation	VEGETATION: Wooded grassland within trial block. Grasses, arable weeds and herbaceous shrubs dominate the flora. Occasional Syzgium guineese and Bauhinia thonningii trees occur within 30 metres. Common shrubs: Aristolochia heppii, Combretum platypetalum, Dilichos kilimandscharicus and Evolvus alsinoides. Herbaceous plants: Lactuca inermis, Pentanisia schweinfurthii, Rhychosia procurrens and Trichodesma physaloides. Arable weeds: Convulvus sagittatatus,Richardia scabra, Schkuhria pinnata, tagetes minuta, Vernonia glabra and Walteria indica. main grasses: Hyperthelia dissoluta, Hetropogon contortus, Sporbolus pyramidalis, Melanis repens, Brachiaria brizantha and Eragrostis patens.
Rotation scheme ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	crop rotation scheme not relevant
Status of vegetation; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	cut over
Major vegetation type; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	semi-deciduous shrub

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	0	2.5	11.1	21.6	20.2	5.1	60.5	3.5	19.7	23.2	16.2
20-34	0	2.8	13.5	24.0	25.0	7.1	72.4	5.9	1.7	7.6	19.9
34-49	0	3.1	11.3	20.0	21.0	6.8	62.2	5.9	3.8	9.7	28.2
49-68	4	2.9	8.7	14.8	16.4	7.9	50.7	3.6	4.3	7.9	41.4
68-112	3	2.2	8.5	14.9	16.9	6.4	48.9	9.1	1.7	10.8	40.3
112-151	0	1.9	7.9	14.5	17.0	8.8	50.1	8.1	3.3	11.4	38.6
151-192	10	2.6	7.8	14.6	16.0	7.0	48	8.7	5.3	14	38.0

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	-	-	-	6.8	16.2
20-34	-	-	-	10.6	19.9
34-49	-	-	-	16.8	28.2
49-68	-	-	-	2.9	41.4
68-112	-	-	-	0.0	40.3
112-151	-	-	-	0.0	38.6
151-192	-	-	-	0.0	38.0

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	5.4	4.5	0.05	-	0.68	0.05	14	0.3	0.0	0.6	0.3	0.3	0.3	1.5
20-34	5.2	4.3	0.04	-	0.48	0.04	12	0.4	0.2	0.4	0.3	0.1	0.0	0.8
34-49	5.2	4.4	0.04	-	0.53	0.03	18	0.3	0.2	0.8	0.3	0.1	0.1	1.3
49-68	5.2	4.7	0.03	-	0.25	0.02	13	0.3	0.0	1.0	0.3	0.1	0.1	1.5
68-112	5.0	4.8	0.02	-	0.14	0.01	14	0.3	0.0	0.6	0.3	0.1	0.0	1
112-151	5.0	4.6	0.02	-	0.10	0.02	5	0.4	0.0	0.8	0.3	0.1	0.1	1.3
151-192	4.9	4.7	0.03	-	0.07	0.01	7	0.4	0.0	0.6	0.3	0.1	0.1	1.1

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 %
0-20	36	4.2	26	2.4	-	0	7
20-34	24	3.3	17	1.7	-	6	0
34-49	33	3.9	14	1.9	-	5	3
49-68	38	3.9	9	0.9	-	0	3
68-112	29	3.5	9	0.5	-	0	0
112-151	37	3.5	9	0.4	-	0	3
151-192	32	3.4	9	0.2	-	0	3

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-20	-	very weak	-	very weak to weak	-	-	very strong	very weak to weak	-	-	-	-
20-34	-	very weak	-	very weak to weak	-	-	very strong	very weak to weak	-	-	-	-
34-49	-	-	-	very weak to weak	-	-	very strong	very weak to weak	-	-	-	-
49-68	-	-	-	very weak to weak	-	-	very strong	very weak to weak	-	-	-	-
68-112	-	-	-	very weak to weak	-	-	very strong	very weak to weak	-	-	-	-
112-151	-	-	-	very weak to weak	-	-	very strong	very weak to weak	-	-	-	-
151-192	-	-	-	very weak to weak	-	-	very strong	very weak to weak	-	-	-	-

Profile description

Ah 0-20 cm	yellowish brown (10YR 5/4, dry) dark brown (7.5YR 3/4, moist)medium sandy loam,moderately coherent medium subangular blocky and moderate fine and medium granular,slightly hard non sticky non plastic,no cutans,few very fine interstitial random pores and few very fine discontinuous tubular random pores highly porous (>60 vol%),many fine and few medium roots,no inclusions,no fragments,few termite channels,non calcareous,clear wavy boundary to,
20-34 cm	brown (7.5YR 5/4, dry) dark brown (7.5YR 3/4, moist)medium sandy loam,moderately coherent massive,slightly hard non sticky non plastic,no cutans,few very fine interstitial random pores and few very fine discontinuous tubular random pores highly porous (>60 vol%),many very fine and few medium roots,no inclusions,no fragments,few termite channels,non calcareous,clear smooth boundary to,
BA 34-49 cm	strong brown (7.5YR 5/6, dry) strong brown (7.5YR 4/6, moist)medium sandy loam,moderately coherent massive,soft non sticky non plastic,common (5-15%) fine faint diffuse mottles 7.5YR6/6 (reddish yellow),no cutans,few very fine interstitial random pores and few very fine discontinuous tubular random pores moderately porous (40-60 vol%),common very fine and few medium roots,no inclusions,no fragments,few termite channels,non calcareous,clear smooth boundary to,
Bt1 49-68 cm	strong brown (7.5YR 5/6, dry) strong brown (7.5YR 4/6, moist)sandy clay loam,moderately coherent massive,slightly hard non sticky non plastic,no cutans,common very fine interstitial random pores and common very fine discontinuous tubular random pores moderately porous (40-60 vol%),few very fine and few medium roots,very few medium irregular manganiferous soft segregations,no fragments,few termite channels,non calcareous,gradual smooth boundary to,
Bt2 68-112 cm	reddish yellow (7.5YR 6/8, dry) strong brown (7.5YR 4/6, moist)sandy clay loam,moderately coherent massive,slightly hard non sticky non plastic,no cutans,common very fine interstitial random pores and tubular pores moderately porous (40-60 vol%),few very fine and few medium roots,few medium spherical soft manganiferous concretions,no fragments,few termite channels and krotovinas,non calcareous,gradual smooth boundary to,
Bt3 112-151 cm	reddish yellow (7.5YR 6/6, dry) strong brown (7.5YR 4/6, moist)sandy clay loam,moderately coherent massive,soft non sticky non plastic,no cutans,common very fine interstitial random pores and common discontinuous tubular random pores moderately porous (40-60 vol%),few very fine and fine roots,few medium spherical hard manganiferous concretions,very few fine gravel strongly weathered gneiss fragments,few termite channels and krotovinas,non calcareous,diffuse smooth boundary to,
Bt4 151-192 cm	reddish yellow (7.5YR 6/6, dry) strong brown (7.5YR 4/6, moist)sandy clay loam,moderately coherent massive,slightly hard non sticky non plastic,no cutans,common very fine interstitial random pores and common discontinuous tubular random pores moderately porous (40-60 vol%),few very fine and fine roots,few medium spherical hard manganiferous concretions,very few coarse gravel strongly weathered gneiss fragments,no,non calcareous,

Kind 1 (parent material) ; Parker (eds), 1984	acidic gneiss
Mode of accumulation or deposition of parent material	residual material
Remarks on Parent Materials	granodiorite gneiss
Soil Depth	192cm
Texture of parent material	sandy
Weathering Resistance	moderate
General characterization of the status of weathering of solid rock	partially or moderately

Occurrence of soil aggradation (McDonald et al., 1984)	not apparent
Intensity of the soil erosion type	slight
Soil erosion type	sheet

Altitude	1526m
Physiographic Unit	saddle between two bornhardts
Physiographic position of the site	lower slope
Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	plateau
Slope	2%
Slope Aspect	east
Form of the slope surrounding the site	straight
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	undulating

Lower limit of a slow permeable or stagnating layer in the profile	68cm
Drainage class ; FAO (2006) - Guidelines for soil description	moderately well
Dry From - To	0-68cm
Flooding frequency (FAO, 1986)	never
Kind of ground water table (USDA, 1979)	no groundwater table observed
Moist From - To	68-192cm
Estimated permeability (class) of least permeable part of the profile	moderate
Estimated run off (class)	rapid
Upper limit of a slow permeable or stagnating layer in the profile	49cm

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
Microrelief Height: variation in height	40
Micro relief type: small-scale differences in relief in the direct vicinity of the site (FAO, 1986)	termite/ant mounds
Microrelief pattern	isolated
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 Zimbabwe 08: Acrisol

Characteristics

Reference soil ZW008: Acrisols

Classification