Soil development and fertility characteristics of inland valleys in the rain forest zone of Nigeria: Physicochemical properties and morphological features

Figures & data

Figure 1  The study sites on a vegetation map of Nigeria.

Figure 2  Brief description of the sampling points in the inland valleys.

Table 1 Morphological characteristics of the soils of the inland valleys

Horizon	Depth (cm)	Color		Texture	Structure	Consistence	Boundary	Others
		Matrix	Mottle
Pedon AK-1, Fluvaquentic Epiaquepts
Ap	0–20	10YR6/4	10YR6/8	SiCL	2 m sbk	fr shs shp	a s	–
A2	20–40	10YR7/3	–	SiL	3 m sbk	fi shs shp	a s	–
Bwg1	40–81	10YR7/2	–	CL	3 m sbk	fi shs shp	a s	Fe/Mn concretion > 15%
Bwg2	81–111	10YR7/2	–	SiL	4 m sbk	fi vs vp	g s	Fe/Mn concretion <10%
Bwg3	111–170	10YR7/2	5Y2/1	SiL	4 m sbk	fi s p	c s	Mn cocretion < 10%
BCg	170–194	10YR7/2	10YR5/6	L	3 m sbk	fi s p	–	Mn concretion > 20% and quartz gravels
Pedon AK-2, Fluvaquentic Epiaquepts
Ag	0–28	2.5Y5/1	7.5YR5/6	SiCL	2 f sbk	fr shs shp	c s	–
A2 g	28–47	10YR8/2	7.5YR5/6	CL	3 f sbk	fr shs shp	c s	–
2Bwg	47–74	10YR5/2	2.5YR3/6	SiCL	3 m sbk	fr shs shp	a s	Fe/Mn concretion > 15%
2Bg	74–109	7.5YR5/1	10YR6/6	SiC	3 m sbk	fr s p	d s	Mn concretion < 10%
2BCg	109–150	7.5YR5/1	10YR6/6	SiCL	3 m sbk	fr shs shp	–	Mn concretion > 15%
Pedon AK-3, Aeric Fragiaquepts
Apg	0–28	7.5Y7/1	10YR5/8	C	2 f sbk	fr shs shp	a s	–
A2feg	28–54	7.5YR4/8	7.5YR2/1	L	ND	ND	c s	Fe concretion > 80%
B1 g	54–100	7.5Y7/1	10YR5/8	C	ND	ND	a s	Fe/Mn concretion < 10%
B2 g	100–158	7.5Y7/1	10YR5/8	C	3 m sbk	fi s p	–	Quartz gravels
Pedon AK-4, Fluvaquentic Epiaquepts
Apg	0–30	2.5Y5/1	7.5YR5/6	C	2 m sbk	fr shs shp	c s	–
Bwg1	30–50	10YR8/2	7.5YR5/6	SiCL	3 m sbk	fr shs shp	c s	–
Bwg2	50–98	10YR5/2	2.5YR4/6	SiCL	3 m sbk	fr shs shp	a s	Fe/Mn concretion > 15%
BCg	98–148	7.5YR5/1	10YR6/6	SiCL	4 c sbk	fr shs shp	–	Mn concretion < 10%
Pedon AK-5, Typic Fragiudepts
Ap	0–20	7.5YR4/4	–	SiCL	2 f gr	fr shs shp	d s	–
AB	20–50	7.5YR4/4	–	SiCL	2 f sbk	fr shs shp	a s	–
2Bw	50–76	10YR5/6	–	SL	3 m sbk	fr shs shp	c s	–
2Bwfeg	76–95	7.5YR4/8	10YR5/6	L	ND	ND	a s	Fe concretion > 80%
3BCg	95–135	7.5Y7/1	10YR5/8	LS	3 m sbk	fi s p	g s	–
3Cg	135–170	7.5Y7/1	10YR5/6	SL	3 m sbk	fi s p	–	–
Pedon BD-1, Fluvaquentic Epiaquepts
Ap	0–21	5YR3/2	–	SCL	2 m sbk	fr s p	c s	–
Bw1	21–50	7.5YR6/1	5YR4/3	C	3 m abk	fi vs vp	c s	–
Bwg2	50–85	7.5YR5/1	2.5YR3/4	C	4 m abk	vfi vs vp	g s	Mn concretion < 10%
Bwg3	85–100	7.5YR5/1	2.5YR4/8	C	4 c abk	vfi vs vp	c s	Mn concretion > 15%
BCg	100–158	7.5YR5/1	10YR5/8	C	4 c abk	fi vs vp	–	Mn concretion > 15%
Pedon BD-2, Fluvaquentic Epiaquepts
Ap1	0–20	7.5YR3/2	–	C	2 f sbk	fr shs shp	c s	–
Apg2	20–52	10YR5/2	7.5YR5/6	SC	3 f sbk	fr s p	a s	–
Bwg1	52–89	2.5Y6/2	2.5YR4/8	C	4 m abk	fi vs vp	a w	–
Bwg2	89–120	2.5Y6/2	10R3/4	C	4 m abk	fi s p	c s	–
BCg	120–165	2.5Y6/1	2.5YR4/8	SCL	3 f sbk	fr s p	–	–
Pedon BD-3, Fluvaquentic Humaquepts
Ap	0–20	10YR3/2	7.5YR4/6	SC	3 f sbk	fr shs shp	c s	–
Bw1	20–73	7.5YR6/1	7.5YR4/6	SC	3 m abk	fi s p	c s	–
Bw2	73–100	7.5YR6/1	–	SCL	4 m abk	fi vs vp	g s	–
BC	100–152+	7.5YR6/2	–	SL	3 m abk	fi vs vp	–	–
Pedon BD-4, Fluvaquentic Humaquepts
Ap	0–18	10YR3/2	5YR4/8	SL	3 f sbk	fr shs shp	c s	–
Bw1	18–30	10YR5/2	5YR4/8	SCL	3 m sbk	fi s p	c s	–
Bw2	30–75	7.5YR6/1	7.5YR5/6	SCL	4 m abk	fi vs vp	a w	–
BC	75–144	7.5YR6/1	–	SL	2 f gr	vfr shs shp	–	–
SiCL, silty clay loam; SiL, silty loam; CL, clay loam; L, loamy; SiC, silty clay; C, clayey; SL, sandy loam; LS, lomy sand; SC, sandy clay; SCL, sandy clay loam; 2, moderate; 3, strong; 4, very strong; m, medium; f, fine; c, coarse; sbk, subangular blocky; abk, angular blocky; gr, granular; fr, friable; fi, firm; vfi, very firm; vfr, very friable; shs, slightly sticky; vs, very sticky; s, sticky; shp, slightly plastic; vp, very plastic; p, plastic; a, abrupt; c, clear; g, gradual; d, diffuse; f, flat; s, smooth; w, wavy; ND, not determined.

Table 2 Selected physicochemical properties of the soils of the inland valleys studied

Horizon	Depth (cm)	Sand (%)	Silt (%)	Clay (%)	Bulk density (g cm^−3)	pH		Exchangeable cations (cmolc kg^−1)						ECEC (cmolc kg^−1)	Organic C (g kg^−1)	Total N (g kg^−1)	Bray-1 P (mg kg^−1)
						H2O	KCl	Ca	Mg	K	Na	Al	H
Pedon AK-1
Ap	0–20	14.4	50.0	35.6	1.65	4.9	4.6	1.27	0.54	0.24	0.13	1.78	0.80	4.76	19.7	1.3	2.4
A2	20–40	26.0	56.2	17.8	0.93	6.1	5.7	1.08	0.71	0.93	0.05	0.56	0.22	3.55	9.3	0.3	1.8
Bwg1	40–81	34.0	42.0	24.0	0.93	8.0	7.3	1.56	1.88	3.53	0.12	0.10	0.02	7.21	9.3	0.4	1.8
Bwg2	81–111	20.4	50.6	29.0	0.99	9.0	8.1	1.81	2.34	4.72	0.24	0.34	0.13	9.58	8.3	0.3	1.8
Bwg3	111–170	20.4	50.6	29.0	1.16	7.7	7.3	2.81	3.70	3.71	0.11	0.19	0.04	10.56	8.2	0.2	2.7
BCg	170–194	12.0	42.0	46.0	1.71	9.1	8.2	3.78	2.48	3.77	0.11	0.06	0.01	10.21	7.6	0.2	2.7
Pedon AK-2
Ag	0–28	14.6	53.4	32.0	1.43	5.1	4.8	0.46	0.30	0.32	0.06	2.89	0.17	4.20	9.3	0.4	1.4
A2 g	28–47	34.0	38.5	27.5	1.19	4.2	4.0	0.89	0.40	0.18	0.14	2.92	0.37	4.90	20.8	1.3	2.1
2Bwg	47–74	12.0	51.5	36.5	1.05	6.0	5.6	1.81	2.14	2.04	0.09	1.90	0.50	8.48	9.5	0.4	0.9
2Bg	74–109	20.0	40.0	40.0	1.68	8.9	8.0	2.74	3.23	4.85	0.24	0.10	0.02	11.18	7.8	0.2	1.0
2BCg	109–150	14.5	51.5	34.0	1.41	8.3	7.5	3.97	3.90	4.91	0.03	0.25	0.05	13.11	7.8	0.3	1.8
Pedon AK-3
Apg	0–28	4.8	40.0	55.2	2.04	4.7	4.2	0.43	0.39	0.18	0.35	2.94	0.36	4.65	14.1	0.7	9.0
A2feg	28–54	36.0	44.0	20.0	1.22	4.8	4.6	1.18	1.77	0.17	0.11	2.40	0.59	6.22	13.6	0.8	1.5
B1 g	54–100	30.5	27.5	42.0	1.04	6.3	6.0	5.91	5.09	0.50	0.13	0.56	0.07	12.26	9.1	0.4	1.2
B2 g	100–158	30.0	22.0	48.0	1.70	7.4	6.8	8.92	4.69	0.77	0.13	0.10	0.03	14.64	8.1	0.3	1.0
Pedon AK-4
Apg	0–30	34.0	20.4	45.6	1.53	4.5	4.1	0.53	4.95	0.17	0.08	2.98	0.32	9.03	15.7	0.8	3.3
Bwg1	30–50	14.2	52.0	33.8	1.74	4.6	4.1	0.24	0.31	0.18	0.05	2.98	0.59	4.35	10.5	0.4	1.8
Bwg2	50–98	18.2	51.8	30.0	1.50	5.6	5.0	0.38	0.63	0.62	0.06	2.93	0.63	5.25	10.3	0.4	1.3
BCg	98–148	20.0	50.0	30.0	1.51	7.3	6.9	1.49	2.33	3.29	0.07	0.27	0.10	7.55	7.8	0.3	1.0
Pedon AK-5
Ap	0–20	18.0	43.8	38.2	1.93	5.0	4.6	0.86	1.14	0.13	0.10	1.01	0.15	3.39	11.8	0.5	3.6
AB	20–50	18.2	44.0	37.8	1.93	4.9	4.6	0.80	0.71	0.15	0.09	1.99	0.83	4.57	11.7	0.5	1.6
2Bw	50–76	53.4	32.4	14.2	1.11	4.7	4.2	0.62	0.57	0.18	0.08	2.80	0.82	5.07	11.9	0.6	1.4
2Bwfeg	76–95	38.0	36.0	26.0	1.13	5.4	5.1	0.27	0.21	0.14	0.02	0.20	0.03	0.87	6.8	2.0	1.8
3BCg	95–135	81.6	8.4	10.0	0.86	5.5	5.3	0.22	0.14	0.13	0.02	0.66	0.07	1.24	6.9	2.3	1.5
3Cg	135–170	76.0	8.8	15.2	0.88	4.6	4.2	0.30	0.34	0.18	0.07	3.25	0.65	4.79	10.9	0.6	3.1
Pedon BD-1
Ap	0–21	64.2	4.0	31.8	0.94	5.0	4.6	4.90	2.53	0.20	0.12	2.73	1.10	11.58	20.1	1.8	2.7
Bw1	21–50	34.0	19.6	46.4	1.08	4.9	4.6	3.42	2.10	0.16	0.10	2.89	1.31	9.98	15.8	1.2	1.8
Bwg2	50–85	26.0	20.0	54.0	1.87	5.0	4.5	4.97	3.07	0.21	0.24	3.14	1.66	13.29	11.6	0.9	1.5
Bwg3	85–100	25.8	16.2	58.0	2.01	4.9	4.6	3.16	2.60	0.18	0.14	3.25	1.70	11.03	9.8	0.7	1.5
BCg	100–158	30.0	16.8	53.2	1.82	5.1	4.8	3.70	2.93	0.22	0.24	2.03	1.27	10.39	9.2	0.5	0.6
Pedon BD-2
Ap1	0–20	40.0	14.3	45.7	0.89	4.9	4.6	6.44	3.19	0.21	0.22	1.97	0.80	12.83	23.9	2.3	3.2
Apg2	20–52	47.5	14.0	38.5	0.91	4.7	4.5	4.77	2.59	0.20	0.14	2.46	0.71	10.87	13.9	0.7	1.2
Bwg1	52–89	38.0	10.0	52.0	1.36	5.0	4.6	3.46	2.47	0.20	0.15	2.02	1.10	9.40	9.9	0.6	10.8
Bwg2	89–120	28.2	11.8	60.0	2.06	5.0	4.6	3.64	2.73	0.19	0.22	2.15	1.17	10.10	9.5	0.5	1.0
BCg	120–165	70.0	8.0	22.0	0.80	4.8	4.4	3.62	3.01	0.20	0.25	2.60	1.72	11.40	9.4	0.5	0.8
Pedon BD-3
Ap	0–20	52.1	10.6	37.3	0.94	5.2	4.8	0.61	0.49	0.17	0.09	2.63	1.70	5.69	20.2	1.2	1.0
Bw1	20–73	48.0	10.0	42.0	1.04	5.8	5.2	0.60	0.74	0.17	0.08	2.95	1.75	6.29	13.4	0.9	1.8
Bw2	73–100	63.5	6.2	30.3	0.96	4.7	4.3	0.71	0.91	0.17	0.10	2.72	1.81	6.42	13.1	0.7	0.6
BC	100–152+	76.0	6.2	17.8	0.80	5.0	4.8	0.63	0.60	0.19	0.25	1.98	1.29	4.94	11.5	0.5	1.8
Pedon BD-4
Ap	0–18	77.4	4.4	18.2	0.73	5.5	5.1	0.60	0.23	0.15	0.04	2.85	0.98	4.85	19.0	1.4	2.1
Bw1	18–30	70.0	6.0	24.0	0.92	5.3	5.0	0.51	0.32	0.16	0.04	2.24	1.29	4.56	4.2	0.4	1.6
Bw2	30–75	68.0	4.3	27.7	1.01	5.1	4.8	0.54	0.51	0.14	0.06	2.82	0.94	5.01	10.0	0.5	1.2
BC	75–144	82.2	3.8	14.0	0.85	5.1	4.9	0.34	0.26	0.15	0.05	2.16	1.87	4.83	8.2	0.3	10.2

Figure 3  Distribution of the active Fe ratio (Feo/Fed) and Al saturation (%) in the soils of the inland valleys.