Soil characteristics and phosphorus accumulation in surface soil in relation to geological and land-use conditions

Figures & data

Figure 1  Location, geological (A) and land-use (B) conditions of the study site. Arrows indicate the flow direction of stream water.

Table 1 Chemical and mineralogical composition of the parent rocks

P. rock^†	SiO2 (%)	Al2O3 (%)	Fe2O3 (%)	MnO (%)	CaO (%)	MgO (%)	K2O (%)	Na2O (%)	P2O5 (%)	TiO5 (%)	IL^‡ (%)	Total (%)	Mineralogy
Granite	71.4	15.8	1.66	0.04	2.71	3.49	3.09	3.49	0.07	0.21	0.71	99.6	Q, F, M
Andesite	52.2	16.0	10.8	0.20	6.80	2.20	1.49	2.20	0.24	0.92	5.20	99.9	F, Q, A, C, M
^†Parent rock.
^‡Ignition loss. A, amphibole; C, chlorite; F, feldspar; M, mica; Q, quartz.

Table 2 Selected physical, chemical and mineralogical properties of the soils

P. rock^†	Land-use type	Texture	IL^‡ (%)	pH	EC (dS m^−1)	CEC^§ (cmolc kg^−1)	K^+ (mg kg^−1)	Na^+(mg kg^−1)	Ca^2+(mg kg^−1)	Mg^2+ (mg kg^−1)	Cl− (mg kg^−1)	F^− (mg kg^−1)	NO^− 3 (mg kg^−1)	SO^2− 4 (mg kg^−1)	B. Mineralogy^¶	C. Mineralogy^††
Granite	Forest	L	1.7	4.6	0.085	4.0	23.2	13.2	15.7	6.3	28.6	1.4	106.9	26.9	Q, F, I, K, H	K, I, H
	Paddy fields	SL	1.5	5.5	0.083	3.3	18.9	18.9	33.2	6.6	13.9	1.6	88.3	61.7
	Orchards	SL	1.3	5.8	0.113	3.0	45.1	45.1	43.5	6.8	20.5	1.7	171.4	34.2
	Upland fields	SL	1.3	6.3	0.178	3.5	43.7	43.7	85.1	15.8	8.2	1.8	407.2	33.1
Andesite	Forest	CL	3.1	4.7	0.170	9.7	47.4	47.4	39.3	14.4	67.3	1.8	354.1	20.9	Q, K, I, F, H, M/V	K, I, H, V/M
	Paddy fields	SiCL	2.2	5.5	0.126	7.1	19.1	23.5	46.9	11.4	18.4	1.9	212.8	60.6
	Orchards	SiCL	2.2	5.2	0.128	8.1	41.5	14.1	48.8	10.2	8.0	1.6	313.0	18.7
	Upland fields	SiCL	2.0	5.3	0.337	7.3	83.0	18.4	180.8	30.1	11.1	1.9	973.6	48.3
^†Parent rock.
^‡Ignition loss at 550°C.
^§Values of cation exchange capacity. pH, EC, cations and anions were determined by 1soil : 10water method.
^¶Bulk mineralogy.
^††Clay mineralogy. CL, clay loam; F, feldspar; H, hydroxy interlayered vermiculite; I, illite; K, kaolinite; L, loam; Q, quartz; SiCL, silt clay loam; SL, sandy loam; V/M, interstratified mineral of mica and vermiculite.

Table 3 Total and fractions of phosphorus (P) in the soils

Parent rock	Land-use type	Inorganic P^†					Organic P (mg kg^−1)	Total P (mg kg^−1)
		Water soluble (mg kg^−1)	Adsorbed (mg kg^−1)	Carbonate (mg kg^−1)	Occluded^‡(mg kg^−1)	Residual (mg kg^−1)
Granite	Forest	0.0	31.8	0.4	0.3	0.03	147.2	179.7
	Paddy fields	4.1	275.5	0.5	0.5	0.01	210.2	491.7
	Orchards	23.1	400.3	0.4	0.1	0.01	359.3	783.3
	Upland fields	49.1	415.4	0.5	0.1	0.07	530.6	995.8
Andesite	Forest	0.0	69.8	0.3	0.4	0.10	175.8	246.4
	Paddy fields	10.1	354.0	0.4	0.4	0.05	217.2	582.2
	Orchards	18.5	404.9	0.4	0.3	0.06	322.1	746.2
	Upland fields	43.7	454.7	0.6	0.3	0.07	561.3	1060.7
^†Determined using the sequential extraction method.
^‡Occluded in Fe-oxides. Detection limit of P determination using the ascorbic acid method: 0.01 mg L^−1.

Table 4 Contents of oxalate-extractable aluminium (Al), iron (Fe) and phosphorus (P), and the degree of P saturation (DPS) of the soils

Parent rock	Land-use type	Al (mmol kg^−1)	Fe (mmol kg^−1)	P (mmol kg^−1)	DPS (mmol kg^−1)
Granite	Forest	83.1	18.9	4.5	8.8
	Paddy fields	45.3	32.0	10.9	28.2
	Orchards	48.7	35.4	25.2	59.9
	Upland fields	52.3	24.6	35.8	93.1
Andesite	Forest	82.2	26.5	6.9	12.7
	Paddy fields	50.8	88.7	20.8	29.8
	Orchards	54.3	40.0	25.5	50.1
	Upland fields	58.4	31.2	36.1	80.6

Figure 2  Fractions of inorganic phosphorus (P) in soils with different parent rocks, (A) granite and (B) andesite and land-use types (AD, adsorbed; CB, carbonate; OC, occluded in Fe-oxides; RS, residual; WS, water-soluble).

Figure 3  Relationship between the contents of water-soluble reactive P and (A) adsorbed P, (B) total P and (C) the degree of P saturation.

Table 5 Effects of parent rocks and land use types on the soil chemical properties and phosphorus accumulation in the soils

	IL(%)	pH	EC(dS m^−1)	K^+ (mg kg^−1)	Na^+(mg kg^−1)	Ca^2+ (mg kg^−1)	Mg^2+(mg kg^−1)	Cl− (mg kg^−1)	F− (mg kg^−1)	NO^− 3 (mg kg^−1)	SO^2− 4 (mg kg^−1)	Fractions of P						Tot. P	DPS (%)
												WS(mg kg^−1)	Ads.(mg kg^−1)	Car.(mg kg^−1)	Occ.(mg kg^−1)	Res.(mg kg^−1)	Org.(mg kg^−1)
Parent rock
Granite	1.45a	5.55a	0.115a	32.73a	30.23	8.88a	8.88a	17.80	1.63	193.45a	38.98	19.08	280.75a	0.45	0.25	0.03	311.83	612.63a	47.50
Andesite	2.38b	5.17b	0.190b	44.75b	25.85	78.95b	16.53b	26.20	1.80	461.25b	37.13	18.08	320.85b	0.43	0.35	0.07	319.10	658.88b	43.30
LSD (0.05)	0.17	0.27	0.029	4.68	NS	7.42	1.65	NS	NS	86.1	NS	NS	48.7	NS	NS	NS	NS	50.15	NS
Land-use type
Forest	2.40a	4.65a	0.128a	35.30a	30.30	27.50a	10.35a	47.95a	47.90a	230.50a	23.90a	0.01a	30.81a	0.35	0.20	0.07	161.50a	213.05a	10.75a
Paddy fields	1.85b	5.50b	0.105a	19.00b	21.20	40.05b	9.00a	16.15b	16.15b	150.55a	61.15b	7.10a	314.75b	0.45	0.45	0.03	213.7a	536.95b	29.05b
Orchards	1.75b	5.50b	0.121a	43.30c	29.6	46.15b	8.50a	14.25c	14.25c	242.20a	26.45a	20.80ab	402.60c	0.40	0.20	0.04	340.70b	764.75c	55.01c
Upland fields	1.65b	5.80b	0.258b	63.35d	31.05	132.95c	22.95b	9.65d	9.65d	690.40b	40.70c	46.42c	435.05c	0.55	0.20	0.07	545.95b	1028.25d	86.85d
LSD (0.05)	0.24	0.38	0.041	6.62	NS	10.5	2.33	1.69	1.69	122.00	11.00	9.34	68.80	NS	NS	NS	90.6	145.00	6.55
LSD (0.05), least significant difference at 95% confidence level; IL, ignition loss at 550°C; values of pH, EC (electrical conductivity), cations and anions determined with 1soil : 10water method; Ads., adsorbed P; Car., carbonate P; DPS, degree of P saturation; Occ., occluded P in Fe-oxides; Org., organic P; Res., residual P; Tot. P, total P; WS, water soluble P.