Characterization of charcoal and firewood ash for use in African peri-urban agriculture

Chemical and Biological Technologies in Agriculture

Table 2 Mean concentration of nutrient elements extracted with aqua regia, H₂SO₄, vinegar, and water in charcoal and firewood ash from five cities in southern Ghana; probability values of a two-way ANOVA using ash type and city as factors

	Charcoal	Firewood	SD	Probability values			CV (± %)
	(mg g⁻¹)		SD	Ash type	City	Ash type × city	CV (± %)
Ca–aqua regia	131	120	26	NS	0.01	NS	16
Ca–H₂SO₄	70	66	36	NS	NS	NS	45
Ca–vinegar	164	148	38	NS	0.02	NS	18
Ca–water	6.4	7.2	1.6	NS	NS	NS	22
Mg–aqua regia	16.8	21.6	6.5	0.01	0.01	NS	25
Mg–H₂SO₄	15.9	20.2	6.1	0.02	0.04	NS	25
Mg–vinegar	14.2	18.7	7.4	0.04	NS	NS	31
Mg–water	0.06	0.08	0.04	NS	NS	NS	34
K–aqua regia	73	69	22	NS	0.01	NS	26
K–H₂SO₄	120	100	38	0.02	< 0.01	< 0.01	17
K–vinegar	136	87	74	0.02	0.02	NS	37
K–water	24	24	3	NS	0.05	0.03	8
Na–aqua regia	3.9	4.2	2.7	NS	< 0.01	0.05	49
Na–H₂SO₄	10.8	12.3	3.2	NS	0.01	NS	23
Na–vinegar	10.1	11.5	4.3	NS	< 0.01	NS	21
Na–water	3.8	4.4	1.7	NS	0.01	0.04	31
P–aqua regia	0.45	0.43	0.13	NS	NS	NS	29
P–H₂SO₄	0.42	0.38	0.12	NS	NS	NS	31
P–vinegar	0.20	0.13	0.06	< 0.01	NS	NS	39
P–water	0.002	0.002	0.001	NS	NS	NS	59

SD = standard deviation of the whole sample group (n = 40); CV = pooled coefficient of variation between replicate samples (n = 4)
NS not significant