Biochar as an organic soil conditioner for mitigating salinity stress in tomato

Figures & data

Table 1. Physical and chemical properties of the starting soil

Properties	Unit	Analysis results
Sand	%	40.20
Silt	%	35.20
Clay	%	26.40
Cation-exchange capacity (CEC)	cmolc kg^–1	36.5
pH	1:2,5 w/s	7.40
EC	dS·m^–1	0.126
CaCO3	%	2.80
Organic matter	%	1.06
NH4 -N	mg kg^−1	1.74
NO3-N	mg kg^−1	0.86
P	mg kg-1	3.20
K	cmolc kg^−1	2.48
Ca	cmolc kg^−1	18.42
Mg	cmolc kg^−1	2.25
Na	cmolc kg^−1	0.21
B	mg kg^−1	0.64
Cu	mg kg^−1	0.76
Fe	mg kg^−1	4.44
Zn	mg kg^−1	0.38
Mn	mg/kg^−1	0.46

Table 2. Chemical characteristics of biochar produced from urban wastes

Properties	Unit	Analysis results
pH	-	7.8
EC (Electrical Conductivity)	dS m^−1	0.38
Total (humic + fulvic)	%	4.9
Organic Nitrogen	%	1.6
C	%	21.54
H	%	1.26
N	%	1.38
O	%	2.1
Pb	mg kg^−1	162
Cd	mg kg^−1	10
Cu	mg kg^−1	393
Ni	mg kg^−1	310
Zn	mg kg^−1	1187
Cr	mg kg^−1	449
Mn	mg kg^−1	549
K	mg kg^−1	10,290
P	mg kg^−1	22,980
Mg	mg kg^−1	7372
Ca	mg kg^−1	57,500
Fe	mg kg^−1	25,680

Table 3. Chemical characteristics of the irrigation water

Properties	Unit	Analysis results
pH	-	7.2
EC (Electrical Conductivity)	dS m^−1	0.11
Total dissolved salts (TDS)	mg L^−1	125
Suspended solids (SS)	mg L^−1	13
Sodium-adsorptions ratio (SAR)		0.45
CaCO3	mg L^−1	0.12
CO3^2	mg L^−1	0.15
HCO3	mg L^−1	1.85
Total N	mg L^−1	85
Cd	mg L^−1	0.05
Cu	mg L^−1	0.2
Ni	mg L^−1	0.01
Zn	mg L^−1	0.2
Cr	mg L^−1	0.01
Mn	mg L^−1	1.2
K	mg L^−1	12
P	mg L^−1	17
Mg	mg L^−1	48
Ca	mg L^−1	27
Fe	mg L^−1	5
Cl	mg L^−1	0.32
Na	mg L^−1	2.2
SO4^−2	mg L^−1	0.12

Table 4. Effects of biochar application on the growth parameters and the physiological parameters of tomato plants grown under salt-stress and non-stress conditions

Applications		Plant height	Shoot fresh weight	Shoot dry weight	Number of leaves	Leaf area	Root fresh weight	Root dry weight	Leaf relative water content	Chlorophyll a fresh weight	Chlorophyll b fresh weight	Total Chlorophyll fresh weight
		cm	g plant^−1	g plant^−1	per plant^−1	cm^2	g plant^−1	g plant^−1	%	mg g^−1	mg g^−1	mg g^−1
S0	BC-0	20.52 ± 0.22b	10.97 ± 1.21e	1.58 ± 0.04d	8.54 ± 0.82 c	473 ± 2.77 c	2.32 ± 0.23d	0.25 ± 0.02b	76.39 ± 1.45a	2.54 ± 0.01b	0.99 ± 0.01e	3.53 ± 0.02 c
	BC-1	28.42 ± 0.19a	26.02 ± 1.34b	2.84 ± 0.03a	9.70 ± 0.95b	873 ± 3.34a	5.83 ± 0.34a	0.47 ± 0.01a	71.67 ± 1.55b	2.45 ± 0.02b	1.56 ± 0.02 c	4.01 ± 0.02b
	BC-2	27.05 ± 0.23a	28.35 ± 1.26a	2.88 ± 0.03a	10.56 ± 1.12a	884 ± 4.55a	4.64 ± 0.55b	0.40 ± 0.02a	79.58 ± 1.75a	2.47 ± 0.02b	1.95 ± 0.02a	4.42 ± 0.04a
S1	BC-0	15.18 ± 0.15 c	9.15 ± 1.14 f	1.27 ± 0.04e	7.43 ± 0.88d	410 ± 2.45 c	1.81 ± 0.34e	0.16 ± 0.01 c	52.78 ± 1.80d	2.25 ± 0.01b	1.04 ± 0.01e	3.29 ± 0.03d
	BC-1	21.72 ± 0.17b	17.48 ± 1.35d	2.10 ± 0.5c	9.17 ± 0.94b	597 ± 2.80b	3.37 ± 0.25 c	0.25 ± 0.01b	65.9 ± 1.96b	2.69 ± 0.02a	1.32 ± 0.02d	4.01 ± 0.05b
	BC-2	20.61 ± 0.25b	19.55 ± 1.35 c	2.22 ± 0.4b	9.30 ± 0.85b	571 ± 3.10b	3.90 ± 0.39 c	0.26 ± 0.02b	58.87 ± 1.54 c	2.31 ± 0.03 c	1.74 ± 0.03b	4.06 ± 0.05b
Salt (S)		***	***	***	***	***	***	***	***	*	***	***
Biochar (BC)		***	***	***	***	***	***	***	**	***	***	***
BC x S		NS	***	***	NS	***	***	***	***	***	***	**

Data represent the average of three replicates ± standard error (or standard deviation). Different letters in each column indicate a significant difference at p ≤ 0.05. *: Significant at p ≤ 0.05; **: Significant at p ≤ 0.01; ***: Significant at p ≤ 0.001; NS: Nonsignificant.

S-0: Non-saline water (as a control).

S-1: 100 mM (NaCl).

B-0: sandy loam soil in 3.5-L pots.

B-1: 5% biochar mixed thoroughly with the sandy loam soil prior to filling into 3.5-L pots.

B-2: 10% biochar mixed thoroughly with the sandy loam soil prior to filling into 3.5-L pots

Figure 1. Effects of biochar application on SOD, CAT, POD activities and proline, H₂O₂, MDA contents of tomato with and without salt stress. Bars with the same letter do not differ at p ? 0.05 level (Duncan’s multiple range test). Summary of two-way MANOVA for effects of salinity (S), biochar (BC), and their interaction: *Significant at p < 0.05; **Significant at p < 0.01; ***Significant at p ? 0.001; NS: nonsignificant.

S-0: Non-saline water (as a control), S-1: 100 mM (NaCl), BC-0: Sandy loam soil in 3.5-L pots, BC-1: 5% biochar mixed thoroughly with the sandy loam soil prior to filling into 3.5-L pots, BC-2: 10% biochar mixed thoroughly with the sandy loam soil prior to filling into 3.5-L pots. SOD: Superoxide dismutase; CAT: Catalase; POD: Peroxidase; H₂O₂: Hydrogen peroxide; MDA: Malondialdehyde

Figure 2. Biplot representation of principal component analysis (PCA) showing the effect of biochar application on tomato plants grown under salt-stress and non-stress conditions. Pl.He: Plant height; SFW: Shoot fresh weight; SDW: Shoot dry weight; Leaf no: Number of leaves; Le.A: Leaf area; RFW: Root fresh weight; RDW: Root dry weight; LRWC: Leaf relative water content; Chla: Chlorophyll a; Chlb: Chlorophyll b; TChl: Total Chlorophyll; H₂O₂: Hydrogen peroxide; CAT: Catalase; POD: peroxidase; MDA: Malondialdehyde. (Salt Control: Non-saline water, Salt: 100 mM (NaCl), Fert. Control: Sandy loam soil in 3.5-L pots, Fert. Biochar-1: 5% biochar mixed thoroughly with the sandy loam soil prior to filling into 3.5-L pots, Fert. Biochar −2: 10% biochar mixed thoroughly with the sandy loam soil prior to filling into 3.5-L pots.).

Figure 3. The effect of biochar applications on the growth of tomato plants grown under salt-stress and non-stress conditions. S-0: Non-saline water (as a control), S-1: 100 mM (NaCl), BC-0: Sandy loam soil in 3.5-L pots, BC-1: 5% biochar mixed thoroughly with the sandy loam soil prior to filling into 3.5-L pots, BC-2: 10% biochar mixed thoroughly with the sandy loam soil prior to filling into 3.5-L pots.