Reference soil Nigeria 02: Regosol

NG002

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 NG002: Regosols

Profile forms part of IITA Toposequence, profile no 066, profile forms part of IITA-LRD-ISM (ISRIC) cooperative program Classification: INRA Sol peu e'volue' non climatique d'apport colluvial hydromorphe. Ochric Ahorizon, ochric epipedon. Climatic data: Normal growing season (with dry period), dry days: 120, interm.days: 70, wet days: 175 Season begins on 7 march. Begin humid on 9 april. Humid period ends on 1 aug. Begin humid on 29 aug. Humid period (62 days) ends on 29 oct. End of season 7 nov. Total length of season is 246 days Brief profile description: Brown, sandy soil with laterite concretions in lower layers, overlaying gravelly, multicoloured clayey material and weathered rock. Parent material: Sandy slope colluvium, containing lateritic gravels in lower part, overlaying very gravelly and very concretionary old colluvium and overlying weathered banded gneiss. Polygenetic soil: buried Bt horizon is most probably genetically not related to overlaying horizons. This assumption seems most plausible, since equivalent Apumo soils can be found without a buried B horizon being present. Horizon BC1: scattered Fe/Mn concretions Horizon 2C: subrounded quartz gravels mainly less than 1cm diameter and rounded hard laterite concretions with brown and black surface colours. Horizon 2Btb: gravel is mainly fine subrounded quartz and laterite concretions; locally larger angular quartz pieces from a broken quartz vein in the underlaying horizon; less lateratie concretions in lower part of horizon. Horizon 3C: weathered micaceous schist and banded gneiss with mainly intact rock structure, many weathered yellow (10YR 7/6) feldspar fragments, many fine mica flakes (muscovite) Imperfectly drained; rapid permeability in sandy material, but impedence on the lower, clayey layers. References: Moormann, F.R. et .al., 1974 The soils of IITA. Veldkamp, W.J., 1979. Land evaluation of valleys in a tropical rain area. Photographs 74:9

Profile description

Ah 0-13 cm	(dark) brown (7.5YR 4/4, moist)loamy coarse sand,moderate fine crumb,loose,many fine medium interstitial pores and common tubular pores,gradual smooth boundary to,
BC1 12-32 cm	(dark) brown (10YR 4/3, moist)loamy sand,weak fine crumb,loose,many fine tubular pores and interstitial pores,few ferruginous concretions manganiferous,diffuse smooth boundary to,
BC2 32-62 cm	(dark) brown (7.5YR 4/4, moist)loamy sand slightly gravelly,very weak fine subangular blocky,very friable,many fine tubular random pores,ferruginous concretions manganiferous,clear wavy boundary to,
C 62-82 cm	(dark) brown (7.5YR 4/4, moist)loamy sand gravelly,weak fine subangular blocky,friable,many fine tubular random pores,ferruginous concretions manganiferous,fine gravel SiO2 fragments,clear wavy boundary to,
2Btb 84-132 cm	reddish brown (5YR 4/4, moist)sandy clay loam very gravelly,moderate fine subangular blocky,hard,many fine distinct clear mottles,common fine tubular pores,medium gravel SiO2/plinthite fragments,clear wavy boundary to,
3C 132-155 cm	sandy loam very gravellyrock,few fine tubular pores,frequent medium gravel weathered mica/feldspar irregular fragments,

Kind 1 (parent material) ; Parker (eds), 1984	gneiss
Kind 2 (parent material) (second entry); Parker (eds), 1984	gneiss
Mode of accumulation or deposition of parent material	colluvial
Mode of accumulation or deposition of parent material (second entry)	colluvial
Texture of parent material	gravelly
Texture of parent material (second entry)	sandy
General characterization of the status of weathering of solid rock	highly
General characterization of the status of weathering of solid rock (second entry)	highly

Occurrence of soil aggradation (McDonald et al., 1984)	absent
Slope stability	stable

Land use or vegetation in the immediate vicinity of the site	arable farming
Rotation scheme ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	shifting - fallow bush
Status of vegetation; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	degraded
Major vegetation type; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	dwarf shrub

Altitude	208m
Physiographic Unit	colluvial slope
Physiographic position of the site	middle slope
Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	low hill
Slope	5%
Slope Aspect	south-west
Form of the slope surrounding the site	straight
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	rolling

Dry From - To	70-132cm
Kind of ground water table (USDA, 1979)	no groundwater table observed
Moist From - To	0-70cm

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	0
Microrelief pattern	none
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 Nigeria 02: Regosol

Characteristics

Reference soil NG002: Regosols

Classification