Factors impacting soil organic carbon pool in different types of Andosols in Toya, Hokkaido, Japan

Figures & data

Figure 1. Soil great group distribution map of Hokkaido, Japan (a) and soil group map of the studied region (b). The soil great group and soil group were shown based on the recent update of the soil map in Hokkaido developed with the comprehensive soil classification system of Japan, (Obara et al. 2016; Kanda et al. 2016)

Table 1. CN ratio of organic matters and C application rate via manure, green manure, and combined organic and synthetic fertilizer

Source	Unit	CN ratio	Vitric Andosols				Silandic Andosols				p-value
			mean	max	min	sd	mean	max	min	sd
Manure	(Mg C ha^−1 yr^−1)	5.6–19.4	1.12	2.87	0	0.94	0.85	5.17	0	1.25	0.21
Green manure	(Mg C ha^−1 yr^−1)	15–25	0.54	1.23	0	0.37	0.40	1.02	0	0.34	0.06
COS	(Mg C ha^−1 yr^−1)	3.1–15.5	0.05	0.19	0	0.06	0.05	0.19	0	0.05	0.87
Total	(Mg C ha^−1 yr^−1)		1.71	4.09	0	1.18	1.31	6.05	0	1.28	0.12

COS: Combined organic and synthetic fertilizers. The p-value represents the result of the t-test between Vitric and Silandic Andosols. Data were adapted from Iwasaki, Endo, and Hatano (2017).

Table 2. Soil physicochemical properties

Physical properties	Unit	Vitric Andosols	Silandic Andosols	Chemical properties	Unit	Vitric Andosols	Silandic Andosols
		12 fields	22 fields			12 fields	22 fields
Sand	(%)	55.7 ± 4.0 b	51.2 ± 2.0 a	SOC content	(g C kg^−1)	21.7 ± 6.1 a	27.9 ± 5.2 b
Silt	(%)	24.3 ± 2.9 a	27.6 ± 2.3 b	STN content	(g N kg^−1)	1.82 ± 0.48 a	2.38 ± 0.42 b
Clay	(%)	20.2 ± 2.4 a	21.3 ± 2.0 a	CN ratio		11.9 ± 1.1 a	11.7 ± 0.6 a
Bulk density	(Mg m^−3)	1.14 ± 0.16 b	1.00 ± 0.12 a	pH		5.94 ± 0.15 b	5.70 ± 0.22 a
Micro-porosity	(m^3 m^−3)	0.300 ± 0.04 a	0.312 ± 0.059 a	EC	(m S m^−1)	6.42 ± 1.32 a	7.27 ± 1.79 b
Macro-porosity	(m^3 m^−3)	0.131 ± 0.052 a	0.138 ± 0.048 a	Available P content	(mg P2O5 kg^−1)	239 ± 97 a	200.± 100 a
Large macro-porosity	(m^3 m^−3)	0.137 ± 0.044 a	0.164 ± 0.056 b	PAC	(mg P2O5 100 g^−1)	1848 ± 357 b	1697 ± 348 a
Total porosity	(m^3 m^−3)	0.568 ± 0.068 a	0.613 ± 0.062 b	Exchangeable K^+ content	(cmolc kg^−1)	1.31 ± 0.25 a	1.25 ± 0.27 a
WFPS	(%)	68.0 ± 12.5 a	65.1 ± 12.4 a	Exchangeable Ca^2+ content	(cmolc kg^−1)	6.67 ± 2.96 a	7.49 ± 3.21 a
Hydraulic conductivity	(10^−6 m s^−1)	1886 ± 1961 a	2340 ± 2797 a	Exchangeable Mg^2+ content	(cmolc kg^−1)	2.41 ± 0.93 b	1.56 ± 0.58 a
Water holding capacity	(m^3 m^−3)	0.431 ± 0.042 a	0.451 ± 0.049 b	CEC	(cmolc kg^−1)	20.5 ± 3.52 a	24.1 ± 3.52 b
Field water capacity	(m^3 m^−3)	0.328 ± 0.040 a	0.330 ± 0.057 a	Base saturation	(%)	52.4 ± 16.9 b	43.8 ± 15.5 a
Available water	(m^3 m^−3)	0.071 ± 0.043 a	0.061 ± 0.019 a

Soil physicochemical properties in the 0–0.15 m layer are presented. Values are mean ± sd. Different lowercase letters indicate a significant difference between the soil types. Micro-porosity: water retained at −6.0 kPa; macro-porosity: pores that drain at 0 to −6.0 kPa. Large macro-porosity: total porosity subtracted by macro-porosity. Water holding capacity: water retained at 0 kPa; soil available water: water drained at −3.0 kPa (field water capacity) to −50.0 kPa (depletion of moisture for normal growth). SOC: soil organic carbon; STN: soil total nitrogen; WFPS: water-filled pore space; EC: electric conductivity; PAC: phosphorus absorption coefficient; CEC: cation exchange capacity. Soil texture (sand, silt, and clay content), bulk density, total porosity, hydraulic conductivity, available water, SOC content, pH, EC, Available P, PAC, exchangeable bases (K+, Ca²⁺, and Mg²⁺), CEC, and base saturation were adapted from Iwasaki, Endo, and Hatano (2017).

Table 3. Pearson’s correlation matrix of soil physicochemical properties

	Sand	Silt	Clay	Bulk density	Micro-porosity	Macro-porosity	Large macro-porosity	Total porosity	WFPS	Hydraulic conductivity	Water holding capacity	Field water capacity	Available water
	(%)			(Mg m^−3)	(m^3 m^−3)				(%)	(10^−6 m s^−1)	(m^3 m^−3)
Sand	Sand
Silt	-0.81*	Silt
Clay	-0.59*	0.04	Clay
Bulk density	0.42*	-0.47*	-0.09	Bulk density
Micro-porosity	-0.02	0.25	-0.36*	0.12	Micro-porosity
Macro-porosity	-0.22	0.17	0.2	-0.71*	-0.59*	Macro-porosity
Large macro-porosity	-0.29	0.2	0.24	-0.70*	-0.59*	0.57*	Large macro-porosity
Total porosity	-0.38*	0.40*	0.09	-0.94*	-0.13	0.67*	0.73*	Total porosity
WFPS	0.10	-0.03	-0.20	0.70*	0.69*	-0.90*	-0.74*	-0.66*	WFPS
Hydraulic conductivity	-0.32	0.15	0.33	-0.33	-0.60*	0.44*	0.62*	0.37*	-0.47*	Hydraulic conductivity
Water holding capacity	-0.34*	0.44*	-0.02	-0.70*	0.43*	0.43*	0.08	0.67*	-0.24	-0.1	Water holding capacity
Field water capacity	0.04	0.12	-0.30	0.05	0.93*	-0.48*	-0.52*	-0.05	0.56*	-0.59*	0.52*	Field water capacity
Available water	0.38*	-0.3	-0.2	-0.32	-0.08	0.41*	0.12	0.30	-0.52*	-0.19	0.30	0.14	Available water
SOC content	-0.49*	0.68*	-0.11	-0.50*	0.50*	0.01	0.09	0.46*	0.09	0.00	0.55*	0.37*	-0.19
STN content	-0.57*	0.75*	-0.08	-0.56*	0.48*	0.09	0.10	0.50*	0.04	0.00	0.62*	0.36*	-0.15
CN ratio	0.24	-0.17	-0.16	0.16	0.17	-0.32	-0.8	-0.16	0.25	-0.04	-0.17	0.09	-0.24
pH	0.41*	-0.46*	-0.03	0.46*	-0.21	-0.04	-0.26	-0.44*	0.11	-0.09	-0.37*	-0.23	-0.06
Electric conductivity	-0.26	0.32	-0.06	-0.27	0.42*	-0.02	0.04	0.28	0.11	0.12	0.46*	0.40*	-0.12
Available P	0.16	-0.27	0.17	0.16	-0.56*	0.29	0.11	-0.17	-0.33	0.36*	-0.39*	-0.60*	0.06
PAC	0.04	0.04	-0.21	0.15	0.56*	-0.3	-0.43*	-0.08	0.50*	-0.28	0.27	0.52*	-0.14
Exchangeable K^+	-0.08	0.12	-0.01	0.02	0.09	0.01	0.07	0.05	0.01	0.21	0.06	0.00	-0.23
Exchangeable Ca^2+	0.09	-0.20	0.20	-0.04	-0.18	0.04	0.13	-0.05	-0.16	-0.02	-0.15	-0.17	0.01
Exchangeable Mg^2+	0.42*	-0.34*	-0.26	0.44*	0.15	-0.28	-0.27	-0.35*	0.25	-0.22	-0.18	0.21	0.08
CEC	-0.52*	0.73*	-0.11	-0.58*	0.54*	0.07	0.12	0.50*	0.03	-0.03	0.66*	0.43*	-0.16
Base saturation	0.46*	-0.62*	0.13	0.33	-0.35*	-0.07	0.00	-0.34	-0.09	-0.04	-0.46*	-0.27	0.13
	SOC content	STN content	CN ratio	pH	Electric conductivity	Available P	PAC	Exchangeable K^+	Exchangeable Ca^2+	Exchangeable Mg^2+	CEC	Base saturation
	(g C kg^−1)	(g N kg^−1)			(m S m^−1)	(mg P2O5 kg^−1)	(mg P2O5 100g^−1)	(cmolc kg^−1)				(%)
SOC content	SOC
STN content	0.97*	STN
CN ratio	0.32	0.06	CN
pH	-0.41*	-0.48*	0.25	pH
Electric conductivity	0.52*	0.55*	0.01	-0.26	Electric conductivity
Available P	-0.35*	-0.39*	0.06	0.38*	-0.05	Available P
PAC	0.32	0.33	0.05	0.03	0.28	-0.58*	PAC
Exchangeable K^+	0.16	0.15	0.10	0.15	0.50*	0.20	0.06	Exchangeable K^+
Exchangeable Ca^2+	-0.11	-0.20	0.32	0.48*	-0.05	0.43*	-0.48*	0.13	Exchangeable Ca^2+
Exchangeable Mg^2+	-0.38*	-0.37*	-0.10	0.19	0.07	-0.04	0.24	0.25	-0.33	Exchangeable Mg^2+
CEC	0.85*	0.87*	0.06	-0.46*	0.60*	-0.31*	0.22	0.23	-0.08	-0.23	CEC
Base saturation	-0.56*	-0.65*	0.27	0.67*	-0.25	0.50*	-0.43*	0.12	0.82*	0.07	-0.58*	Base saturation

Soil physicochemical properties in the 0–0.15 m layer were used to obtain Pearson’s correlation coefficient. * p < 0.05; SOC: soil organic carbon; STN: soil total nitrogen; WFPS: water-filled pore space; EC: electric conductivity; PAC: phosphorus absorption coefficient; CEC: cation exchange capacity.

Table 4. Soil carbon and nitrogen related properties

Soil type		SOC content		Change in SOC content from 2001–2003 to 2012		WESOC		NO3^–N		SOC stock
		0–0.15 m	0.15–0.30 m	0–0.15 m	0.15–0.30 m	0–0.15 m	0.15–0.30 m	0–0.15 m	0.15–0.30 m	0–0.15 m	0.15–0.30 m	0–0.30 m
		(g C kg^−1)		(g C ha^−1 yr^−1)		(mg C kg^−1)		(mg N kg^−1)		(Mg C ha^−1)
Vitric Andosols	12 sites	21.7 ± 6.1 a	19.4 ± 6.8 a	0.24 ± 0.61 b		45.5 ± 23.7 a	36.9 ± 17.7 a	23.8 ± 9.3 a	1.3 ± 0.3 a	36.5 ± 9.3 a	35.3 ± 10.1 a	71.5 ± 15.3 a
Silandic Andosols	22 sites	27.9 ± 5.2 b	26.9 ± 4.8 b	−2.80 ± 0.39 a		46.8 ± 19.4 a	30.6 ± 17.1 a	30.8 ± 19.4 a	1.6 ± 17.1 a	41.7 ± 7.8 b	44.5 ± 7.4 b	86.4 ± 12.7 b
Soil type		STN content		CN ratio		Available N		NH4^+-N		STN stock
		0–0.15 m	0.15–0.30 m	0–0.15 m	0.15–0.30 m	0–0.15 m	0.15–0.30 m	0–0.15 m	0.15–0.30 m	0–0.15 m	0.15–0.30 m	0–0.30 m
		(g C kg^−1)				(mg N kg^−1)		(mg N kg^−1)		(Mg C ha^−1)
Vitric Andosols	12 sites	1.82 ± 0.48 a	1.84 ± 0.47 a	11.9 ± 1.1 a	10.7 ± 2.9 a	37.0 ± 9.8 b	45.6 ± 10.5 b	1.0 ± 0.6 a	8.7 ± 9.9 a	3.05 ± 0.70 a	3.02 ± 0.79 a	6.06 ± 1.22 a
Silandic Andosols	22 sites	2.38 ± 0.42 b	2.25 ± 0.43 b	11.7 ± 0.6 a	11.9 ± 0.7 b	31.8 ± 9.3 a	35.7 ± 10.4 a	1.4 ± 0.8 a	8.1 ± 3.7 a	3.55 ± 0.63 b	3.76 ± 0.69 b	7.33 ± 1.11 b

Soil carbon and nitrogen related properties in the 0–0.15 m, 0.15–0.30 m, and 0–0.30 m layers are presented.

Values are mean ± sd. Lowercase letters indicate a significant difference between the soil types. SOC: soil organic carbon; STN: soil total nitrogen; WESOC: water extracted soil organic carbon; Available N: Thermal extracted nitrogen suggested by Sakaguchi, Sakurai, and Nakatuji (2010). SOC content, SOC stock, and available N in the 0–0.15 m layer, and changes in SOC content from to 2001–2003 were adapted from Iwasaki, Endo, and Hatano (2017).

Figure 2. The relationship between the C application rate via organic matter and SOC stock. Error bar represents a standard deviation

Figure 3. The relationship between the micro-porosity and SOC stock in the 0–0.15 m layer. Error bar represents a standard deviation

Figure A1. Relationship between sand content and soil physicochemical properties in the 0–0.15 m layer. The error bar represents the standard deviation. SOC: soil organic carbon; STN: soil total nitrogen; CEC: cation exchange capacity

Figure A2. Relationship between (a) SOC content and STN content; (b) WESOC and available N. The error bar represents the standard deviation. SOC: soil organic carbon; STN: soil total nitrogen; WESOC: water extracted soil organic carbon; Available N: Thermal extracted nitrogen suggested by .Sakaguchi, Sakurai, and Nakatuji (2010)

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