Hardwood biochar as an alternative to reduce peat use for seed germination and growth of Tagetes patula

Figures & data

Table 1. Experimental peat-biochar mixtures with different substitution ratios of peat by hardwood biochar.

Treatment	Peat (%, v v^−1)	Biochar (%, v v^−1)
BC0	100	0
BC2	98	2
BC5	95	5
BC10	90	10
BC15	85	15
BC25	75	25
BC50	50	50
BC75	25	75
BC100	0	100

Figure 1. The grading curve of fractional content of biochar. Percentage ratio of fractional mass retained for each fractional diameter in logarithmic scale.

Figure 2. Effect of peat substitution by biochar on initial and final (a) pH_KCl and (b) electrical conductivity (mS m⁻¹) (mean ± standard error). Different letters indicate different groups according to Tukey HSD test (α = 0.05), lower case for differences among treatments for initial pH and EC, upper case for differences among treatments for final pH and EC. Stars indicate significant differences between initial and final for each treatment according Wilcoxon signed-rank test (p < .05).

Table 2. The total content of nutrients in the different treatments in the end of the experiment.

Treatment	N (g 100 g^−1)	C (g 100 g^−1)	P (g 100 g^−1)	K (g 100 g^−1)	Ca (g 100 g^−1)	Mg (g 100 g^−1)
BC0	0.65a	42bc	0.00e	0.00g	0.18f	0.05d
BC2	0.54b	39bc	0.00e	0.03f	0.20f	0.05d
BC5	0.47cd	40bc	0.01d	0.03f	0.50de	0.05d
BC10	0.42cde	40bc	0.00e	0.08e	0.51cd	0.07c
BC15	0.38e	44b	0.01b	0.13c	0.65b	0.09b
BC25	0.72a	53a	0.00e	0.10d	0.43e	0.08b
BC50	0.49bc	39bc	0.02a	0.22a	0.65b	0.09b
BC75	0.28f	26d	0.01c	0.19b	0.59bc	0.09b
BC100	0.41de	37c	0.01b	0.23a	0.81a	0.16a

Note: Different letters indicate different groups according to Dunn test (α = 0.05).

Table 3. The content of available nutrients in the different treatments in the end of the experiment.

Treatment	P(mg 100 g^−1)	K(mg 100 g^−1)	Ca(mg 100 g^−1)	Mg(mg 100 g^−1)
BC0	4.8bc	13f	265b	81a
BC2	2.1d	15f	182d	53c
BC5	4.4c	26e	227c	63b
BC10	4.6bc	42d	309a	79a
BC15	4.7bc	47d	221cd	54c
BC25	4.3c	69b	267b	63b
BC50	5.3b	55c	183d	36d
BC75	4.5c	43d	119e	20e
BC100	7.9a	78a	267b	29d

Note: Different letters indicate different groups according to Dunn test (α = 0.05).

Figure 3. Effect of peat substitution by biochar on final germination percentage (%) of Tagetes patula seeds (mean ± standard error). Different letters indicate different groups according to Dunn test (α = 0.05).

Figure 4. Correlation analysis (Pearson’s correlation coefficient, r) between germination (%), plant growth parameters and growing media characteristics (pH_KCl, EC, available P, K, Ca and Mg). Black colour indicates positive and grey colour negative correlation; asterisks indicate statistically significant correlations (p < .05).

Figure 5. Effect of peat substitution by biochar on (a) plant height (mm), (b) plant diameter (mm), (c) shoot dry biomass (g plant⁻¹) and (d) true leaf area (mm² plant⁻¹) of Tagetes patula. Grey dot represents the mean. Different letters indicate different groups according to Dunn test (α = 0.05).

Figure 6. Effect of peat substitution by biochar on (a) root dry biomass (g plant⁻¹), (b) total root length (cm plant⁻¹), (c) root volume (cm³ plant⁻¹) and (d) root average diameter (mm) of Tagetes patula (mean ± standard error). Grey dot represents the mean. Different letters indicate different groups according to Dunn test (α = 0.05).

Table 4. Effect of peat substitution by biochar on the nutrient content in plant shoots.

Treatment	N(g 100^−1)	C(g 100^−1)	P(g 100^−1)	K(g 100^−1)	Ca(g 100^−1)	Mg(g 100^−1)
BC15	2.11a	3.8a	0.17c	1.9d	0.10c	0.23b
BC25	0.93c	3.7a	0.19c	2.6c	0.41b	0.17c
BC50	1.29b	3.6a	0.46a	8.1a	0.91a	0.18c
BC75	0.87c	3.7a	0.30b	4.5b	0.54b	0.17c
BC100	0.81c	3.8a	0.15c	4.8b	0.04c	0.29a

Note: Different letters indicate different groups according to Dunn test (α = 0.05).

Figure 7. Quadratic regression between pH and (a) shoot dry biomass, (b) root dry biomass, (c) plant height and (d) plant diameter.