Reference soil Bhutan 01: Podzol

BT001

Podzols mainly occur in cool temperate and moist regions on coarse textured materials. Areas of Podzols have also been recorded from wet, tropical regions, notably the Amazon basin, southern central Africa and southeast Asia.

Characteristics

Soils having a spodic horizon (a dark coloured subsurface horizon with illuvial amorphous alumino-organic substances) within 200 cm from the soil surface, underlying an albic, histic, umbric or ochric horizon, or an anthropedogenic horizon less than 50 cm thick.

Podzols are probably the most extensively researched group of soils.

Distribution of Podzols (rough estimation supplied by soilgrids)

Reference soil BT001: Podzol

Classification

WRB 2014
Entic-Umbric-Protoandic- Podzol

Local classification:	Yellow Hill Soil

Location:

Lame Goempa Research Forest, Jakar (Bumthang dzongkhag), Bhutan

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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
0-20	-	0.817	2.464	3.96	5.733	9.97	23	14.3	35.352	49.7	27.265
20-23	-	1.509	3.186	5.148	6.815	9.716	26.3	12.2	32.182	44.4	29.26
23-37	-	0.718	5.165	7.927	11.863	12.94	38.6	11.3	30.859	42.2	19.205
37-80	-	3.7	7.338	9.839	14.634	11.679	47.1	8.6	21.863	30.5	22.443
80-120	-	7.943	21.266	24.243	24.021	9.598	87	3.3	6.239	9.5	3.484
120-155	-	1.992	4.858	21.364	34.649	16.486	79.4	4.9	11.219	16.1	4.529

Other physical data

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
0-20	0.63	-	-	-	27.265
20-23	0.83	-	-	-	29.26
23-37	0.57	-	-	-	19.205
37-80	1.12	-	-	-	22.443
80-120	1.46	-	-	-	3.484
120-155	1.38	-	-	-	4.529

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	5.13	4.87	0.073	-	5.18	0.306	16.912	-	3.789	1.58	0.099	0.123	0	1.8
20-23	4.95	3.92	0.033	-	1.53	0.135	11.326	-	6.293	0.148	0.074	0	0	0.2
23-37	5.61	4.71	0.016	0.107	2.447	0.171	14.291	-	-	0.074	0	0	0	0.1
37-80	5.54	4.62	0.012	-	0.65	0.082	7.927	-	0.864	0	0	0	0	-
80-120	5.3	4.09	0.011	-	0.07	0.02	3.5	-	1.318	0	0	0	0	-
120-155	5.2	4.14	0.015	-	0.17	0.041	4.22	-	2.452	0.089	0.156	0.022	0	0.3

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	7	24.176	-	-	5.6	68	-
20-23	1	15.503	-	-	6.5	97	-
23-37	1	17.163	-	-	-	-	-
37-80	-	7.884	-	-	-	-	-
80-120	-	3.746	-	-	-	-	-
120-155	5	6.514	-	-	2.8	89	-

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
0-20	-	90	0.477	1.136	0.146	3.785	1.226	-	-	-	1.629
20-23	-	70	0.12	0.553	0.045	2.678	0.544	-	-	-	1.173
23-37	11.02	99	0.256	1.879	0.423	4.942	1.691	-	-	-	2.785
37-80	10.41	75	0.08	0.74	0.199	2.526	0.651	-	-	-	0.926
80-120	-	10	0.009	0.052	0.005	1.157	0.118	-	-	-	0.027
120-155	-	19	0.016	0.073	0.006	1.575	0.158	-	-	-	0.093

Depth (cm)	CaSO4.2H2O %	P Bray mg/kg	P Olsen mg/kg	pH CaCl2	clay_noncarbonate % w/w	clay_carbonate % w/w	phosphorus4 mg/kg	phosphorus1 mg/kg	total_sulfur % w/w
0-20	-	-	-	4.66	27.265	-	99.503	0.021	0.03
20-23	-	-	-	4.32	29.26	-	20.73	0.208	0.007
23-37	-	-	-	5.16	19.205	-	0	0	0.046
37-80	-	-	-	4.92	22.443	-	34.73	0	0.007
80-120	-	-	-	4.39	3.484	-	0	1.893	0
120-155	-	-	-	4.29	4.529	-	0	0.935	0

Profile description

Ah 0-20 cm	dark brown(10YR 3/3, moist) ; moderate granular ; friable ; no cutans; very few (0-2%) distinct black fine (2-6 mm) mottles; common high (15-40%) pores; common medium (6–20 mm) both hard and soft ; no rocks (0%) ; common ; clear (2-5 cm) smooth; nearly plane surface boundary to
Ae 20-23 cm	brownish yellow(10YR 6/6, moist) ; moderate subangular blocky ; friable ; no cutans; no (0%) mottles; many high (15-40%) pores; few fine roots; none ; no rocks (0%) ; few burrows (unspecified) ; gradual (5-15 cm) broken; discontinuous boundary to
B1 23-37 cm	strong brown(7.5YR 5/8, moist) ; weak fine/thin crumbly ; very friable ; very few clay cutans; no (0%) mottles; many high (15-40%) pores; few fine roots; none ; no rocks (0%) ; few burrows (unspecified) ; gradual (5-15 cm) smooth; nearly plane surface boundary to
B2 37-80 cm	strong brown(7.5YR 5/8, moist) ; moderate subangular blocky ; firm ; no cutans; no (0%) mottles; common medium (5-15%) pores; few fine few very fine roots; none ; many (15-40%) strongly weathered ; no biological activity ; clear (2-5 cm) smooth; nearly plane surface boundary to
2CB 80-120 cm	yellowish brown(10YR 5/6, moist) ; unsorted sand weak fine/thin ; very friable ; no cutans; no (0%) mottles; none pores; few fine few very fine roots; none ; dominant (> 80%) strongly weathered ; no biological activity ; gradual (5-15 cm) smooth; nearly plane surface boundary to
3BC 120-155 cm	strong brown(7.5YR 5/8, moist) ; medium sand weak fine/thin single grain ; friable ; no cutans; very few (0-2%) distinct fine (2-6 mm) mottles; few low (2-5%) pores; very few very fine roots; few fine (2–6 mm) iron (ferruginous) hard ; common (5-15%) strongly weathered coarse artefacts (> 20 mm) ; no biological activity ; clear (2-5 cm) smooth; nearly plane surface boundary to
3CB 155- cm	unsorted sand weak fine/thin ; very friable ; no cutans; no (0%) mottles; none pores; very few very fine roots; none ; dominant (> 80%) strongly weathered ; no biological activity ;

Age of the land Surface	older pleistocene, with periglacial influence, commonly the recent soil formation on younger over older, preweathered materials.
Kind 1 (parent material) ; Parker (eds), 1984	marl
Remarks on Parent Materials	Mica schists of Thimphu Formation

Intensity of the soil erosion type	slight
Soil erosion type	water erosion or deposition
Classification of total area affected by erosion and deposition	0%-5%

Land improvements ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	vegetation moderately disturbed
Land use or vegetation in the immediate vicinity of the site	selective felling
Remarks on Land Use / Vegetation	Blue pine (P. wallichiana) with a.o. Rhododendron sp., Daphne sp., Vaccinium sp. and ferns in understorey
Major vegetation type; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	closed forest (continuous tree layer, crowns overlapping, large number of tree and shrub species in distinct layers)

Altitude	2985m
Hierarchy of major landforms	high-gradient mountain
Physiographic Unit	middle slope (back slope) in undulating to mountainous terrain
Physiograpy description	Roadcut on hillside
Slope	09%
Slope Aspect	north
Form of the slope surrounding the site	concave
Slope gradient %	35.0%

Drainage class ; FAO (2006) - Guidelines for soil description	moderately well drained
Flooding	none
Depth to groundwater table	> 1000cm
Drainage class - intergrade; FAO (2006) - Guidelines for soil description	well drained

Average size of stone	stones (6-20 cm);B
Surface stoniness class (FAO (2006) - Guidelines for soil description)	few (2-5%)

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Reference soil Bhutan 01: Podzol

Characteristics

Reference soil BT001: Podzol

Classification