Short-term effects of raw rice straw and its derived biochar on greenhouse gas emission in five typical soils in China

Figures & data

Table 1 Physico-chemical properties of rice (Oryza sativa L., cv.) straw, biochars (BC350 and BC500), and five typical soils (YT, AS, SY, CS, and FQ).

	Straw	BC350	BC500	YT	AS	SY	CS	FQ
pH (H2O)	/^a	9.50	10.5	5.05	8.04	7.90	6.31	7.77
C (g kg^–1)	379	529	572	5.14	14.3	5.80	26.6	16.3
N (g kg^–1)	10.5	10.7	15.8	0.06	-^b	0.20	1.81	0.20
C/N	42.1	57.7	42.2	99.9	/	33.8	17.1	95.1
Ash (g kg^–1)^c	128	286	332	/	/	/	/	/
SA (m^2g^–1)	/	3.62	34.3	/	/	/	/	/
PV(cm^3g^–1)	/	0.02	0.06	/	/	/	/	/
APD(nm)	/	10.8	6.42	/	/	/	/	/
DOC (g kg^–1)	/	4.69	0.77	0.62	0.64	0.64	1.00	0.70
Sand (%)	/	/	/	25.0	38.5	51.7	17.0	18.1
Silt (%)	/	/	/	54.2	55.5	40.7	71.7	71.3
Clay (%)	/	/	/	20.8	6.0	7.6	11.3	10.6

^a /, not determined; ^b, below detection limit; ^c, heating at 900°C.YT, Yingtan; AS, Ansai; SY, Songyuan; CS, Changshu; FQ, Fengqiu; H₂O, water; C, carbon; N, nitrogen; SA, BET-N₂ surface area; PV, pore volume; APD, average pore diameter; DOC, dissolved organic C.

Figure 1 Dynamics of soil carbon dioxide (CO₂) emission from five soils (a, b, c, d and e stand for soil from YT, Yingtan; AS, Ansai; SY, Songyuan; CS, Changshu; and FQ, Fengqiu respectively) with different treatments and 28 d incubation. Soil, Soil + Straw, Soil + BC350, and Soil + BC500 stand for soil only, soil + 5% rice (Oryza sativa L., cv.) straw, soil + 5% straw biochar produced at 350°C, and soil + 5% straw biochar produced at 500°C, respectively. C, carbon.

Figure 2 Dynamics of soil methane (CH₄) emission from five soils (a, b, c, d and e stand for soil from YT, Yingtan; AS, Ansai; SY, Songyuan; CS, Changshu; and FQ, Fengqiu respectively) with different treatments and 28 d incubation. Soil, Soil + Straw, Soil + BC350, and Soil + BC500 stand for soil only, soil + 5% rice (Oryza sativa L., cv.) straw, soil + 5% straw biochar produced at 350°C, and soil + 5% straw biochar produced at 500°C, respectively. C, carbon.

Figure 3 Dynamics of soil nitrous oxide (N₂O) emission from five soils (a, b, c, d and e stand for soil from YT, Yingtan; AS, Ansai; SY, Songyuan; CS, Changshu; and FQ, Fengqiu respectively) with different treatments and 28 d incubation. Soil, Soil + Straw, Soil + BC350, and Soil + BC500 stand for soil only, soil + 5% rice (Oryza sativa L., cv.) straw, soil + 5% straw biochar produced at 350°C, and soil + 5% straw biochar produced at 500°C, respectively. N, nitrogen.

Figure 4 Cumulative emissions of (A) carbon dioxide (CO₂), (B) methane (CH₄), and (C) nitrous oxide (N₂O) from five soils (YT, Yingtan; AS, Ansai; SY, Songyuan; CS, Changshu; and FQ, Fengqiu) with different treatments and 28 d incubation. Soil, Soil + Straw, Soil + BC350, and Soil + BC500 stand for soil only, soil + 5% rice (Oryza sativa L., cv.) straw, soil + 5% straw biochar produced at 350°C, and soil + 5% straw biochar produced at 500°C, respectively. C, carbon; N, nitrogen.

Table 2 The pH, ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^–-N)_, and dissolved organic carbon (DOC) in the different treatments with 28 d incubation

Soil	Treatment	pH	NH4^+-N (mg kg^-1)	NO3^--N (mg kg^-1)	DOC (g kg^-1)
YT	Soil	5.17 ± 0.04b	1.15 ± 0.35c	7.40 ± 2.8c	0.92 ± 0.05b
	Soil + Straw	4.77 ± 0.10c	0.90 ± 0.19c	41.4 ± 6.2a	1.15 ± 0.03a
	Soil + BC350	4.90 ± 0.03c	2.04 ± 0.22b	29.1 ± 2.0b	0.82 ± 0.03b
	Soil + BC500	5.64 ± 0.16a	4.79 ± 0.47a	0.26 ± 0.00d	0.81 ± 0.04b
AS	Soil	8.27 ± 0.17b	0.38 ± 0.09b	17.9 ± 8.6a	0.99 ± 0.10b
	Soil + Straw	7.36 ± 0.05c	1.47 ± 0.26a	31.1 ± 1.3a	1.14 ± 0.17a
	Soil + BC350	8.01 ± 0.08b	1.10 ± 0.39ab	16.9 ± 2.4a	0.96 ± 0.12b
	Soil + BC500	8.56 ± 0.03a	0.62 ± 0.26b	21.3 ± 11.9a	0.83 ± 0.12c
SY	Soil	7.90 ± 0.17a	1.30 ± 0.52a	35.3 ± 14.0a	0.89 ± 0.10b
	Soil + Straw	7.33 ± 0.09b	1.81 ± 1.12a	30.9 ± 11.7a	1.28 ± 0.13a
	Soil + BC350	7.50 ± 0.02b	1.30 ± 0.28a	37.9 ± 6.8a	0.88 ± 0.11b
	Soil + BC500	7.98 ± 0.10a	1.13 ± 0.41a	50.0 ± 11.0a	0.78 ± 0.12b
CS	Soil	6.43 ± 0.11b	5.80 ± 0.22a	99.27 ± 2.3a	0.99 ± 0.07b
	Soil + Straw	6.56 ± 0.19b	1.83 ± 0.30b	16.9 ± 1.7c	1.42 ± 0.10a
	Soil + BC350	6.48 ± 0.10b	6.23 ± 0.86a	58.4 ± 6.1b	1.03 ± 0.07b
	Soil + BC500	7.29 ± 0.02a	2.73 ± 0.74b	84.4 ± 11.9a	1.01 ± 0.10b
FQ	Soil	7.95 ± 0.06b	0.97 ± 0.34a	96.9 ± 21.5a	0.71 ± 0.13c
	Soil + Straw	7.36 ± 0.02d	1.64 ± 0.29a	23.7 ± 1.8b	1.26 ± 0.20a
	Soil + BC350	7.65 ± 0.10c	1.84 ± 0.16a	78.6 ± 7.6a	0.95 ± 0.14b
	Soil + BC500	8.13 ± 0.02a	1.66 ± 0.64a	75.7 ± 11.3a	0.71 ± 0.14c

Different letters for each parameter indicate significant difference [p < 0.05, one-way analysis of variance (ANOVA)] between the treatments in one soil.Soil, soil only; Soil + Straw, soil + 5% rice (Oryza sativa L., cv.) straw; Soil + BC350, soil + 5% BC350; Soil + BC500, soil + 5% BC500; YT, Yingtan; AS, Ansai; SY, Songyuan; CS, Changshu; FQ, Fengqiu.

Table 3 Total carbon dioxide (CO₂) equivalent emission [global warming potential (GWP), mg CO₂ kg^–1 soil] following different treatments with 28 d incubation

Soil	Treatment	GWP (mg CO2 kg^–1 soil)
YT	Soil	1179 ± 149b
	Soil + Straw	5499 ± 173a
	Soil + BC350	1099 ± 51b
	Soil + BC500	1104 ± 66b
AS	Soil	200 ± 38c
	Soil + Straw	6327 ± 21a
	Soil + BC350	721 ± 20b
	Soil + BC500	152 ± 26c
SY	Soil	588 ± 67c
	Soil + Straw	5701 ± 216a
	Soil + BC350	1252 ± 83b
	Soil + BC500	440 ± 14d
CS	Soil	2203 ± 788b
	Soil + Straw	9596 ± 703a
	Soil + BC350	2549 ± 524b
	Soil + BC500	1208 ± 59c
FQ	Soil	599 ± 53c
	Soil + Straw	5404 ± 527a
	Soil + BC350	1051 ± 151b
	Soil + BC500	344 ± 69d

Different letters for each parameter indicate significant difference [p < 0.05, one-way analysis of variance (ANOVA)] between the treatments in one soil.Soil, soil only; Soil + Straw, soil + 5% rice (Oryza sativa L., cv.) straw; Soil + BC350, soil + 5% BC350; Soil + BC500, soil + 5% BC500; YT, Yingtan; AS, Ansai; SY, Songyuan; CS, Changshu; FQ, Fengqiu.

Table 4 The correlation coefficients between cumulative emission of greenhouse gases (GHGs) and characteristics of five type soils following different treatments after 28 d incubation.

Soil	property	CH4	CO2	N2O
YT	pH	0.94**	–0.60*	0.24
	DOC	–0.37	0.84**	–0.22
	NO3-N	/	/	–0.58*
AS	pH	0.71**	–0.92**	–0.71**
	DOC	–0.43	0.64*	0.50
	NO3-N	/	/	0.27
SY	pH	0.70*	–0.78**	0.34
	DOC	–0.43	0.94**	–0.08
	NO3-N	/	/	–0.31
CS	pH	0.66*	–0.30	–0.53
	DOC	–0.51	0.95**	0.55
	NO3-N	/	/	–0.36
FQ	pH	0.69*	–0.85**	–0.83**
	DOC	–0.58*	0.92**	0.93**
	NO3-N	/	/	–0.88**

/, not analyzed; *, p < 0.05; **, p < 0.01.CH₄, methane; CO₂; carbon dioxide; N₂O, nitrous oxide; DOC, dissolved organic carbon; NO₃-N, nitrate nitrogen; YT, Yingtan; AS, Ansai; SY, Songyuan; CS, Changshu; FQ, Fengqiu.