Table 1.

Summary of the retrieved articles used for this systematic review.

S/N	Country	Biochar feedstock	Soil type	Biochar pH	Biochar N (g/kg)	Biochar OC (g/kg)	Soil pH	Soil N (g/kg)	Soil OC (g/kg)	Reference
1	Bangladesh	Bagasse	Silt loam	9.5	6.5	597	6.2	–	23.2	[55]
2	China	poplar saw dust	–	–	–	–	6.42	1.72	16.98	[56]
3	China	Wheat straw	Hydragric anthrosol/Halic acrisol	9.51	13.3	–	6.38	1.56	22.8	[57]
				9.51	13.3	–	5.05	1.9	18.1
4	China	Wheat straw	Stagnic anthrosols	10.5	11.29	513.17	5.6	–	20.26	[58]
5	China	wheat straw	littoral clay salt soil	9.4	5.6	467	8.5	0.9	11.5	[39]
6	China	wheat straw	Irragric Anthrosols	9.4	5.9	467	5.7	1.32	14.6	[50]
7	China	wheat straw	Anthrosol	10.3	10.7	490	7.35	2.1	20.3	[59]
8	China	Wheat	–	10.48	10.7	513.17	5.3	1.82	20.26	[60]
				10.48	10.7	513.17	5.64	1.45	14.62
9	China	Maize straw	Histosols	9.8	20	624.2	6.8	1.87	15.39	[40]
				10.4	16.4	655.5
10	South Korea	Sesame	–	10.1	10.9	710.7	4.95	0.58	2.02	[61]
11	South Korea	Bamboo	–	9.71	12.8	764	4.95	0.58	2.03	[48]
12	South Korea	Rice husk	–	–	5.7	454	5.4	–	12.79	[62]
13	Japan	poultry excreta	Alluvial	10	26.7	284.5	5.24	1.4	14.5	[63]
14	China	wheat straw	–	–	–	–	5.99	1.81	20.11	[46]
							6.21	1.79	18.76
							4.89	1.59	17.7
15	China	wheat straw	Hydragric Anthrosol	10.4	6	470	6	1.8	20.1	[64]
16	China	Bamboo	Loamy paddy	9.84	4.1	709	6.03	0.8	6.1	[65]
17	China	Maize straw	Sandy Loam		0.11	25.3		0.1	20.2	[66]
18	China	Rape straw	Orthic Entisol/Regosol	8.9		625.8	6.3	0.1	11.1	[41]
19	China	Pig manure compost/Maize straw/peanut husk/municipal waste	Entic Hydragric Anthrosol	6.84	16.8	508	5.82	3.08	33	[67]
				9.74	11.08	520.7
				9.16	10.2	341
				7.88	10.5	295.3
20	Thailand	Mangrove	Vertisol	7.8	2.8	585	7	0.6	17.72	[68]
21	China	Rice straw	–	9.1	8.1	670.7	6.7	1.2	11	[69]
22	Thailand	Eucalypt wood	Loamy soil	7.98	5.4	614.3	5	0.8	7.1	[43]
23	Thailand	Mangrove tree	Clay loam	5.8	2.9	282.3	7.5	0.6	0.53	[52]
24	China	Rice husk	Orthic Anthrosols	9.1	6.2	465.4	7.8	0.42	4.8	[70]
25	China	Rice husk	Gleyi-Stagnic Anthrosol	10.9	0.81	238	7	2.83	26.6	[71]
26	China	rice straw/waste wood	Silt loam	–	–	–	6.5	1.93	18.16	[72]
27	China	Wheat straw	hydroagric Stagnic Anthrosol	10.4	5.9	467	6.5	1.8	24	[73]
28	Thailand	Mangrove	Alfisols	7.94	2.4	659	6.17	0.45	4.3	[74]
29	Cambodia	Rice straw	Sandy	–	15.1	503.4	4.79	0.53	5.25	[38]
30	Vietnam	Rice straw	–	10.1	1.9	209	5.7	1.63	12.55	[75]
31	China	Wheat straw	Latosolic soil	8.1	3.29	605	7	1.87	31.2	[76]
32	Japan	Rice husk	Haplic andosol	8.4	4.01	427	5.8	4.2	58.7	[77]
33	Japan	Rice husk	Haplic andosol	7.07	3.15	361.7	6.63	2.7	32.3	[78]
34	China	Rice straw/Bamboo	–	10.2	10.7	478	5.2	3.2	20.6	[79]
				9.81	5.9	815
35	China	Rice straw	Stagnic anthrosol	9.8	5.8	500	5.31	1.98	18.4	[49]
36	China	Wheat straw	Stagnic Anthrosol	10.4	5.9	467	6.5	1.8	23.5	[80]
37	China	Rice straw	–	10.58	10.8	472.1	5.39	2.8	49.3	[81]
38	China	Rice straw	Stagnic Anthrosol	10.4	5.9	467	6.5	1.8	23.5	[82]
39	China	Rice straw	Anthrosols	9.16	13.3	620	6	1.79	16.6	[51]
40	China	Rice straw	Hydragric anthrosol	10.1	7.5	426	7.4	1.03	21.9	[83]
41	China	wheat straw	–	8.91	14.15	–	6.38	1.56	22.8	[84]
				9.63	4.72	–
				4.64	12.26	–
				3.74	4.5	–
42	Vietnam	Rice straw	Alluvial	–	12.1	353.2	6.21	10.3	12.6	[44]
43	Malaysia	Rice straw	Dystric Fluvisol	10.08	–	–	5.9	6	240.9	[85]
44	China	wheat straw	Stagnic Anthrosol	9.1	5.8	418.3	5.1	2.1	18.9	[86]
45	China	Wheat straw	Stannic Anthrosol	9.3	5.8	418.3	5.1	1.62	17.5	[87]

Alternate Wetting and Drying = AWD, Continuous Flooding = CF, Intermittent Irrigation = IT, mgt = Management.