Effect of cultivar type and soil properties on cadmium concentrations in potatoes

Figures & data

Table 1. Summary of sites and details of soil and plant sampling.

Year	Sites	Location	No. of cultivars	Sampling details
Potato cultivar study
2015	2 research trial sites	Pukekohe Waikato	8 2	Potato cultivars were grown in 3 replicate plots (double-row, 1.8 × 1.5 m), arranged in a randomised design. Soil and plant sampling were undertaken at harvest. For each plot 5 soil cores (150 mm depth) were collected and combined to form a single composite sample and a single tuber was collected from 5 plants within each plot. In addition a composite soil sample (25 × 150 mm) was taken along a 100 m transect.
	1 research trial sites	Lincoln	10	Potato cultivars were grown in 4 replicate plots (single row, 3.5 × 0.76 m), arranged in a randomised design. Soil and plant sampling were undertaken at harvest. For each plot, 5 soil cores (150 mm depth) were collected and combined to form a single composite soil sample and a single medium sized tuber collected from 5 plants within each plot. In addition a composite soil sample (150 mm depth) was taken along a 100 m transect.
Potato survey
2016 and 2017	35 research trial and commercial sites	Canterbury Pukekohe Waikato Manawatū	2	At each commercial site 3 plots were established randomly across the field. These plots were the width of the planting row, by a length of ∼1.5 m sufficient to encompass a minimum of 5 plants. Within each plot, 5 tubers and 5 soil cores (150 mm depth) were collected At research sites, potatoes were grown and sampled as described above for the 2015 research trials at Pukekohe and Waikato.

Table 2. Potato tuber Cd concentrations (mg kg⁻¹ DW) in different cultivars at Pukekohe, Waikato and Lincoln.

Cultivar	Pukekohe	Waikato	Lincoln
Agria	0.063abA	0.133aB	0.195abC
Bondi	0.073ab		0.150c
Crop 39	0.053bc		0.200ab
Desiree	0.063ab		0.275d
Ilam Hardy			0.158c
Innovator			0.205a
Moonlight	0.080aA	0.103bB	0.185bC
Nadine	0.113d		0.160c
Russet Burbank	0.070ab		0.123e
Russet Ranger	0.040c		0.115e

Note: Mean followed by the same lowercase letter within a site are not significantly different (P < 0.05) or not significantly different between sites (capital letters).

Figure 1. Comparison of cadmium concentrations (mg kg⁻¹ DW) in the flesh or peel in potato cultivars from the Lincoln research trial site.

Figure 2. (A) Total soil cadmium concentration (mg kg⁻¹) in each region (MW = Manawatū–Wanganui; Puke = Pukekohe). The dashed line is the TFMS trigger 1 value. (B) Mean cadmium concentrations (mg kg⁻¹ DW) in potatoes for each region. (C) The transfer coefficient for each region. Boxes depict the 25th and 75th percentile values, with horizontal lines plotted within boxes representing the median value. Whiskers show the 10th and 90th percentile values and the points the 5th and 95th percentile values.

Table 3. Selected soil properties from the survey sites (0–15 cm).

Site	pH	Olsen P	Total P	Total C	Total N	K	Mg	Ca	Na	CEC	Total Cd	Total Zn	Cl	Sand	Silt	Clay
		mg kg^−1	mg kg^−1	(%)	(%)	cmol kg^−1	cmol kg^−1	cmol kg^−1	cmol kg^−1	cmol kg^−1	mg kg^−1	mg kg^−1	mg kg^−1	%	%	%
1	6.0	28	n.d.	2.5		0.2	9.3	0.7	0.19	16	0.18	55	51	23	54	23
2	6.0	25	835	1.9	0.2	0.1	6.9	0.5	0.14	13	0.12	72	13	7	70	23
3	5.3	20	604	2.0	0.2	0.2	6.0	0.3	0.16	12	0.14	48	39	35	47	18
4	5.0	44	1031	3.5	0.3	0.5	6.8	0.5	0.20	17	0.19	79	24	11	69	20
5	5.4	36	740	1.6	0.2	0.6	6.5	0.9	0.09	17	0.14	71	12	15	62	23
6	5.7	47	1030	3.3	0.3	0.5	8.2	0.8	0.24	15	0.16	82	38	7	67	26
7	5.4	30	947	2.5	0.3	0.4	6.6	0.7	0.12	14	0.14	79	38	13	62	25
8	5.6	25	819	2.1	0.2	0.4	6.4	0.5	0.13	12	0.13	84	30	10	68	22
9	5.5	29	1074	2.5	0.3	0.8	6.0	0.7	0.09	13	0.16	86	33	13	73	14
10	5.5	50	774	1.3	0.1	0.5	4.2	0.5	0.10	9	0.11	72	58	28	55	17
11	6.1	48	892	2.4	0.2	0.4	6.6	1.3	0.19	13	0.15	90	29	13	66	21
12	5.2	51	1156	2.5	0.3	0.7	9.3	1.5	0.19	18	0.24	96	57	6	67	27
13	5.0	78	1852	7.7	0.6	0.9	16.9	2.2	0.24	36	0.25	100	160	1	35	64
14	5.6	84	2141	7.8	0.6	0.5	23.9	1.6	0.22	38	0.21	88	70	1	43	56
15	5.2	55	1954	8.7	0.6	0.6	18.8	2.1	0.19	38	0.29	95	37	1	34	65
16	7.2	144	3418	2.4	0.2	0.9	12.9	0.7	0.08	15	0.30	103	4	12	61	27
17	5.4	92	2296	7.3	0.6	1.8	14.2	2.7	0.15	34	0.27	105	18	1	28	71
18	6.6	76	n.d.	1.6	n.d.	0.9	10.4	1.1	0.20	16	0.27	51	<10	21	20	59
19	6.9	303	3971	1.5	0.1	1.1	13.8	1.6	0.12	19	0.69	136	13	4	21	75
20	6.8	255	3161	2.3	0.2	1.3	13.9	1.5	0.11	19	0.54	139	49	4	24	72
21	6.0	136	2033	2.7	0.2	0.8	8.1	0.8	0.11	17	0.56	82	21	10	29	61
22	6.4	76	1732	3.7	0.3	0.7	11.9	0.8	0.11	19	0.40	82	17	8	34	58
23	6.8	146	2259	3.0	0.3	1.6	15.9	1.2	0.15	22	0.46	128	18	8	29	63
24	5.9	190	2839	2.2	0.2	0.8	9.2	1.1	0.21	19	0.54	122	28	7	30	63
25	6.4	171	4878	4.4	0.4	1.7	14.5	1.9	0.16	27	0.54	134	19	12	48	40
26	6.1	150	2540	2.5	0.2	1.6	10.3	1.5	0.07	20	0.52	125	12	7	30	63
27	5.9	74	1944	7.1	0.6	1.1	19.4	1.5	0.26	30	0.33	77	43	44	42	14
28	5.8	24	1073	6.0	0.5	0.5	13.0	0.9	0.22	25	0.43	71	34	8	31	61
29	6.6	54	n.d.	6.3	n.d.	0.8	13.5	1.4	0.10	22	0.77	76	<10	40	41	19
30	6.7	53	2590	4.0	0.4	0.8	13.1	1.2	0.07	20	0.74	98	42	31	47	22
31	6.0	65	1947	2.8	0.3	0.7	9.4	1.0	0.12	17	0.41	144	46	28	39	33
32	6.7	31	1611	3.6	0.4	0.8	10.9	1.3	0.07	18	0.32	68	n.d.	27	50	23
33	6.2	41	1953	4.2	0.4	1.0	7.1	1.2	0.05	17	0.50	83	3	28	51	21
34	6.9	73	2445	3.6	0.4	1.2	11.8	1.4	0.05	18	0.77	98	6	30	50	20
35	5.9	70	1981	3.6	0.4	1.0	7.5	1.0	0.08	19	0.53	125	9	27	47	26

n.d. not determined

Table 4. Single relationships of Cd concentration in potatoes (DW) with soil properties.

Soil property	Significance level (p-value) of the relationship
pH	0.065
Olsen P	0.189
Exchangeable K	0.058
Exchangeable Ca	0.573
Exchangeable Mg	0.371
Exchangeable Na	0.002 S
CEC	0.156
Base saturation	0.023 S
Total Cd	0.709
Total Zn	0.578
Total P	0.052
Total N	0.056
Total C	0.070
C/N	0.122
Total Fe	0.477
Total Mn	0.529
Total S	0.621
Total Al	0.010 S

Note: S indicates a statistically significant relationship at the 5% level.

Significant relationship were positive except for base saturation.

Table 5. Coefficients of soil properties and their significance levels

Soil property	Coefficient	SE	% variation
Al	0.1275	0.0139	41.5***
Mn	−0.0535	0.0113	0.3***
Na	0.0199	0.0069	9.5**
Fe	−0.0479	0.0105	0.7***
P	−0.0677	0.0103	4.8***
Zn	0.0304	0.0112	0.1**

**, ***Significant at P < 0.01 and 0.001 levels, respectively.