Reference soil Zimbabwe 01: Lixisol

ZW001

Lixisols occur dominantly in the drier parts of the tropics and subtropics. Their high base status is partly due to less leaching, partly to admixture from airborne dust from adjacent desert regions.

Characteristics

Soils having an argic horizon (a subsurface horizon with a 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 either: 100 cm from the soil surface, or 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 50 percent or more in the major part between 25 and 100 cm from the soil surface.

Distribution of Lixisols (rough estimation supplied by soilgrids)

Reference soil ZW001: Lixisols

(1)Profile is located under grass/clover,adjacent to the Experimental Farm trials. (2)Grass identifications include Panicum repens, Heteropogon contortus, Eragrostis tenwifolium, Eragrostis pseudosclerantha, Digitaria ciliaris, Hyparrhenia filipendula, Chloris pychinothrix, Sporobolus pyramidalis, and Bothriochloa insculpta. The clover species is Trifolium. (3)A wide range of crops are grown in the Farm trials. During the wet summer season, maize, sunflower, soyabeans, groundnuts, sorghum, pearl and finger millets, potatoes, summer wheat, pulses, bambara nuts and cowpeas. During the dry winter season, winter wheat, winter barley and potatoes are grown. (4)There is evidence of termite activity, particularly in the upper horizons (0-30 cms). Covered channels, constructed by the insects since the pit was dug, extend down to 150 cms. A number of termite and ant fungal gardens were observed in the field examinations, and one large termite garden was collected for display purposes. (5)Common, small, white fungal colonies occur in the first horizon (0-27 cms). Two areas of expanding mycelia developed on the pit face at about 100 cms depth. (6)Many mites were observed on the profile face. In addition to these and the termites, colonies of small black ants and centipede insects were observed. (7)Field texturing reveals a somewhat inactive clay fraction. The presence of sand grains in the texturing was also observed - fine in the upper horizons, medium-sized in the middle horizons, and with coarse grains in the lower horizons. Texturing also reveals the evidence of water stable aggregates. The amount of these aggregates appears to decrease with depth from 27 - 160 cms. (8)Very rare fragments of weathered gabbro in the soil profile, which were generally yellowish brown/black/whitish in colour and between 3 - 5 mm. in size. (9)One small, (230 mm) subrounded boulder of gabbro was extracted from the pit. A skin of weathered gabbro surrounded the extracted core. (10)Very fine pores (<1 mm) were observed from 49 cms to depth. Some of these pores were caused by roots, which had since decomposed. (11)Slight colour variegations were noted from 47 cms to depth but were difficult to code. (12)Water permeability into peds of the upper horizons (0 - 27 cms) was slower than those of lower horizons, presumeably because of the presence of organic matter in the topsoils. (13)Iron/manganese stains were observable from 23 cms, became more numerous with depth, but also less prominent. (14)Under virgin conditions, the site would normally be located under Brachystegia spiciformis/Julbernardia globiflora woodland. These species, along with Uapaca kirkiana, Acacia sp. and Erithrina sp., presently occur in an undisturbed area of the adjacent Royal Harare Golf Course. Occasional large Brachystegia trees occur within the grounds of the Experimental Farm, one of which is 30 m from the pit. (15)Examination of the soil profile reveals the presence of shiny ped surfaces, which are recorded in the profile description as cutans on ped face

Classification

WRB 2006

Cutanic- Lixisol (Manganiferric Clayic Rhodic)

17-89 cm	argic horizon
89-160 cm	ferralic horizon

17-89 cm	argic horizon
89-160 cm	ferralic horizon

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Niti-Haplic Lixisol

Ferric Luvisol

0-27 cm	ochric A horizon
17-89 cm	argic B horizon
-	nitic

0-27 cm	ochric A horizon
17-89 cm	argillic B horizon
-	ferric

Local classification:	Harare 5E.2 series

Other classification

USDA-SCS (1975)

Paleustalf ustic fine mixed isothermic

Land use

Major crops	maize
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)	continuously irrigated
Land use or vegetation in the immediate vicinity of the site	high level arable farming
Remarks on Land Use / Vegetation	VEGETATION: Under grass adjacent to crop trials. Grasses: Panicum repens, Heteropogon contortus, Eragrostis tenwifolium, Eragrostis preudosclerantha, Digitaria ciliaris, Hyparrhenia filipendula, Chloris pychinothrix, Sporobolus pyramidalis and Bothriochloa insculpta; clover species is Trifolium. LAND USE: a wide range of crops is grown: during summer maize, sunflower, soybeans, groundnuts, sorghum, pearl and finger millets, potatoes, summer wheat, pulses, bambara nuts and cowpeas; during winter: winter wheat, winter barley and potatoes
Rotation scheme ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	continuous crop rotation

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
0-17	0	0	1	3	7	3	14	5	8	13	72
17-27	0	0	0	1	3	2	6	2	5	7	86
27-47	0	0	1	2	3	1	7	7	2	9	83
47-89	0	0	0	1	2	1	4	3	6	9	86
89-100	0	0	0	1	3	2	6	5	10	15	76
100-130	0	0	0	1	2	2	5	8	11	19	75
130-160	0	0	3	1	3	2	9	6	12	18	73

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
0-17	1.36	-	-	-	72
17-27	1.29	-	-	-	86
27-47	1.29	-	-	-	83
47-89	1.23	-	-	-	86
89-100	1.29	-	-	-	76
100-130	1.29	-	-	-	75
130-160	-	-	-	-	73

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
0-17	1.36	-	-	40	38	36	-	35	27
17-27	1.29	-	-	40	38	36	-	34	30
27-47	1.29	-	-	40	38	36	-	34	30
47-89	1.23	-	-	43	39	36	-	32	28
89-100	1.29	-	-	46	41	39	-	36	32
100-130	1.29	-	-	46	41	39	-	36	32

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
0-17	5.8	4.9	-	-	1.40	-	-	-	-	5.8	4.0	0.2	0.1	10.1
17-27	5.7	4.6	-	-	1.10	-	-	-	-	4.9	3.6	0.2	0.1	8.8
27-47	5.6	4.6	-	-	0.80	-	-	-	-	4.9	3.6	0.2	0.1	8.8
47-89	5.7	4.9	-	-	0.50	-	-	-	-	4.7	3.6	0.2	0.1	8.6
89-100	5.9	5.3	-	-	0.30	-	-	-	-	4.5	3.8	0.2	0.1	8.6
100-130	5.9	5.3	-	-	0.30	-	-	-	-	4.5	3.8	0.2	0.1	8.6
130-160	6.0	5.3	-	-	0.20	-	-	-	-	4.8	3.9	0.2	0.1	9

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 %
0-17	63	16.1	22	5	-	-	1
17-27	62	14.1	16	4	-	-	1
27-47	62	14.1	17	3	-	-	1
47-89	66	13.0	15	2	-	-	1
89-100	73	11.8	16	1	-	-	1
100-130	73	11.8	16	1	-	-	1
130-160	74	12.1	16	1	-	-	1

Profile description

Ah 0-17 cm	dark reddish brown (5YR 3/4, dry) dark reddish brown (5YR 3/3, moist)clay,moderate fine and medium subangular blocky and moderate very fine granular,hard (dry) very friable slightly sticky slightly plastic (moist),no cutans,no pores moderately porous (40-60 vol%),common very fine and fine roots,no inclusions,no fragments,frequent termite channels and mycelium,non calcareous,clear smooth boundary to,
17-27 cm	dark reddish brown (2.5YR 3/4, dry) (2.5YR 3/3, moist)clay,moderate fine and medium subangular blocky and moderate very fine granular,hard (dry) very friable slightly sticky slightly plastic (moist),no cutans,common very fine roots,few medium irregular manganiferous soft segregations,no fragments,frequent termite channels,non calcareous,clear smooth boundary to,
Bt1 27-47 cm	dark red (2.5YR 3/6, dry) dark red (2.5YR 3/6, moist)clay,moderate to strong fine and medium subangular blocky and moderate very fine granular,friable sticky slightly plastic,common (5-15%) fine faint clear mottles (2.5YR 3/6),broken thin slickensides on pedfaces,no pores,few very fine roots,frequent medium irregular manganiferous soft segregations,no fragments,few termite channels,non calcareous,gradual smooth boundary to,
Bt2 47-89 cm	dark red (2.5YR 3/6, dry) dark red (2.5YR 3/6, moist)clay,moderate to strong fine and medium subangular blocky and moderate very fine granular,friable sticky slightly plastic,common (5-15%) fine faint clear mottles 2.5YR3/4 (dark reddish brown),broken moderately thick pressure on pedfaces,few very fine discontinuous exped and inped tubular random pores,few very fine and fine roots,frequent medium irregular manganiferous soft segregations,very few fine gravel strongly weathered gabbro fragments,few termite channels,non calcareous,gradual smooth boundary to,
Bw1 89-100 cm	dark red (2.5YR 3/6, dry) dark red (2.5YR 3/6, moist)clay,weak to moderate fine and medium subangular blocky and moderate very fine granular,very friable sticky slightly plastic,common (5-15%) fine faint clear mottles 2.5YR3/4 (dark reddish brown),patchy thin pressure cutans throughout,few to common very fine discontinuous exped and inped tubular random pores,few very fine and fine roots,frequent medium irregular manganiferous soft segregations,very few fine gravel strongly weathered gabbro fragments,few termite channels,non calcareous,gradual smooth boundary to,
Bw2 100-160 cm	dark red (2.5YR 3/6, dry) dark red (2.5YR 3/6, moist)clay,moderate medium subangular blocky,very friable sticky slightly plastic,common (5-15%) fine faint clear mottles 2.5YR3/4 (dark reddish brown),patchy thin pressure cutans throughout,few very fine discontinuous exped and inped tubular random pores,few very fine and fine roots,frequent medium irregular manganiferous soft segregations,very few fine gravel strongly weathered gabbro & quartz fragments and very few coarse gravel fresh gabbro fragments,few termite channels,non calcareous,

Kind 1 (parent material) ; Parker (eds), 1984	coarse-grained basic igneous rock
Mode of accumulation or deposition of parent material	residual material
Remarks on Parent Materials	gabbro
Soil Depth	160cm
Texture of parent material	clayey
Weathering Resistance	moderate
General characterization of the status of weathering of solid rock	highly

Occurrence of soil aggradation (McDonald et al., 1984)	absent
Intensity of the soil erosion type	slight
Soil erosion type	sheet
Slope stability	stable

Altitude	1506m
Physiographic Unit	edge of high watershed plateau
Physiographic position of the site	upper slope
Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	plateau
Slope	1%
Slope Aspect	south
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	well
Dry From - To	0-27cm
Flooding frequency (FAO, 1986)	never
Kind of ground water table (USDA, 1979)	no groundwater table observed
Moist From - To	27-300cm
Estimated permeability (class) of least permeable part of the profile	moderate
Estimated run off (class)	slow

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)
Slaking of aggregates by tillage, rainfall or frost (USDA/SCS, 1979)	no surface slaking/crusting observed
Microrelief Height: variation in height	15
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 01: Lixisol

Characteristics

Reference soil ZW001: Lixisols

Classification