Biochar and manure influences tomato fruit yield, heavy metal accumulation and concentration of soil nutrients under wastewater irrigation in arid climatic conditions

Figures & data

Table 1. Electrical conductivity (EC), pH, organic matter, phosphorus (P), lead (Pb), copper (Cu), zinc (Zn), nickel (Ni) and chromium (Cr)

	Biochar	Cow manure	Groundwater	Wastewater
EC	2.38 (µs cm^−1)	nd	732 (µs cm^−1)	1720 (µs cm^−1)
pH	8.2	nd	nd	nd
Organic matter	71 (%)	35 (%)	nd	nd
P	3.46 (mg g^−1)	1.47 (mg g^−1)	nd	nd
Pb	–*	2.54 (mg g^−1)	0.05 (ppm)	0.05 (ppm)
Cu**	–	–	–	–
Zn**	0.09 (mg g^−1)	0.32 (mg g^−1)	0.73 (ppm)	4.88 (ppm)
Ni**	0.006 (mg g^−1)	0.039 (mg g^−1)	0.48 (ppm)	0.33 (ppm)
Cr**	0.02 (mg g^−1)	0.02 (mg g^−1)	–	0.13 (ppm)

**Data from Tahir et al. (2018) and Ghori et al. (in preparation).

*Concentration below the detectable limit by atomic absorption spectrophotometer.

nd, no data.

Table 2. Three-way ANOVA results for F- and P-values

Aboveground plant biomass	F	P
Irrigation treatment	78.25	0.0000
Organic amendment (biochar, manure and mixture of biochar and manure)	122.41	0.0000
Application rate	81.65	0.0000
Irrigation treatment × organic amendment	0.79	0.5065
Irrigation treatment × application rate	0.036	0.8508
Organic amendment × application rate	184.47	0.0000
Irrigation treatment × organic amendment × application rate	2.947	0.0689
Root biomass
Irrigation treatment	143.53	0.0000
Organic amendment	77.78	0.0000
Application rate	10.42	0.0032
Irrigation treatment × organic amendment	2.26	0.1028
Irrigation treatment × application rate	7.51	0.0105
Organic amendment × application rate	18.83	0.0000
Irrigation treatment × organic amendment × application rate	17.33	0.0000
Fruit yield (g dry weight)
Irrigation treatment	41.85	0.0000
Organic amendment	51.81	0.0000
Application rate	11.06	0.0025
Irrigation treatment × organic amendment	2.64	0.0689
Irrigation treatment × application rate	1.22	0.2779
Organic amendment × application rate	14.63	0.0000
Irrigation treatment × organic amendment × application rate	2.91	0.0708
Soil pH
Irrigation treatment	71.11	0.0000
Organic amendment	21.46	0.0000
Application rate	43.20	0.0000
Irrigation treatment × organic amendment	30.70	0.0000
Irrigation treatment × application rate	0.25	0.6207
Organic amendment × application rate	8.36	0.0041
Irrigation treatment × organic amendment × application rate	11.63	0.0002
Mineral nitrogen of soil
Irrigation treatment	0.48	0.4930
Organic amendment	16.82	0.0000
Application rate	25.81	0.0000
Irrigation treatment × organic amendment	0.303	0.8224
Irrigation treatment × application rate	0.93	0.5132
Organic amendment × application rate	23.37	0.0000
Irrigation treatment × organic amendment × application rate	0.75	0.4787
Soluble mineral phosphorus of soil
Irrigation treatment	15.21	0.0005
Organic amendment	16.82	0.0000
Application rate	49.04	0.0000
Irrigation treatment × organic amendment	6.26	0.0022
Irrigation treatment × application rate	9.42	0.0047
Organic amendment × application rate	19.31	0.0000
Irrigation treatment × organic amendment × application rate	9.24	0.0008

Values in bold represent significant results at P < 0.05.

Figure 1. Stover biomass, root biomass and fruit yield (dry mass) of tomato under groundwater and wastewater irrigation (mean ± SD). Bars with different letters represent a significant difference between treatments under given irrigation treatment (P < 0.05). Bars with * indicate significant differences between groundwater and wastewater irrigation for a given organic amendment treatment (P < 0.05). B: biochar, M: manure, BM: biochar–manure mixture, 0.5: amendment at 0.5 kg m⁻², 1: amendment at 1 kg m⁻².

Table 3. Concentration (µg g⁻¹) and NUE (calculated as average yield/concentration of a given heavy metal) of Pb, Cu, Zn, Ni and Cr in tomato fruits irrigated with wastewater (n = 1, pool of three samples)

Treatment	Pb	NUE for Pb	Cu	NUE for Cu	Zn	NUE for Zn	Ni	NUE for Ni	Cr	NUE for Cr
Control	3.89	23.6	10.3	8.89	28.27	3.25	–	nd	0.79	116.3
B 0.5	3.19	66.3	–	nd	27.64	7.65	0.43	491.9	–	nd
B 1	2.50	144.9	–	nd	30.45	11.8	1.46	248.1	–	nd
M 0.5	–*	nd^1	–	nd	27.72	9.38	6.37	40.84	–	nd
M 1	2.94	101.5	–	nd	28.23	10.5	1.54	193.7	–	nd
BM 0.5	4.82	39.9	1.18	163.3	36.47	5.28	–	nd	–	nd
BM 1	4.20	37.2	0.79	198.0	30.61	5.11	–	nd	–	nd

*Concentration below detectable limits, by atomic absorption spectrophotometer. ¹No data.

Table 4. pH, mineral nitrogen (N) (mg g⁻¹ soil) and soluble mineral phosphorous (P) (mg g⁻¹ soil) of soil after harvest of tomato plants (mean ± SD)

Groundwater irrigation	Treatment	pH	Total mineral N (mg g^−1 soil)	Soluble mineral P (mg g^−1 soil)
	Control	7.58 ± 0.005^e	1.66 ± 0.61^b	0.89 ± 0.49^b
	B 0.5	7.85 ± 0.087^bc	1.28 ± 0.14^b	1.52 ± 1.14^b
	B 1	7.65 ± 0.040^d	0.78 ± 0.03^b	4.06 ± 3.69^ab
	M 0.5	7.82 ± 0.032^bc**	13.1 ± 1.84^a	4.93 ± 1.45^a
	M 1	7.91 ± 0.065^a	0.96 ± 0.23^b	1.45 ± 0.32^b
	BM 0.5	7.75 ± 0.042^d	1.42 ± 0.35^b	1.99 ± 1.50^b
	BM 1	7.77 ± 0.050^c	0.84 ± 0.48^b	1.63 ± 1.04^b
Wastewater irrigations	Control	7.83 ± 0.017^c**	1.63 ± 0.17	0.17 ± 0.12^d
	B 0.5	8.06 ± 0.032^a**	1.03 ± 0.21	2.51 ± 1.92^c
	B 1	8.04 ± 0.020^a**	0.98 ± 0.29	4.75 ± 2.36^b
	M 0.5	7.65 ± 0.045^d	10.0 ± 7.71	15.1 ± 3.25^a**
	M 1	7.95 ± 0.055^b	1.21 ± 0.52	1.77 ± 0.06^c
	BM 0.5	7.84 ± 0.066^c	1.37 ± 0.40	3.28 ± 0.58^bc
	BM 1	7.88 ± 0.070^bc	0.66 ± 0.12	2.53 ± 1.66^bc

Values within the column of a given irrigation treatment followed by different letters are significantly different at P < 0.05. **Significantly higher values between wastewater and groundwater irrigation for a given amendment treatment.

Tahir, S., Gul, S., Ghori, S. A., Sohail, M., Batool, S., Jamil, N., … Butt, M. R. (2018). Biochar influences growth performance and heavy metal accumulation in spinach under wastewater irrigation. Cogent Food And Agriculture, 4, 1–12.

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Ghori, S. A., Gul, S., Tahir, S., Sohail, M., Batool, S., Shahwani, M. N., … Butt, M. R. (in preparation). Influence of wood-derived biochar on morphological and physiological traits of spinach under groundwater and wastewater irrigation. Journal of Environmental Engineering and Landscape Management.

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