Cadmium Concentrations in New Zealand Wheat: Effect of Cultivar Type, Soil Properties, and Crop Management

Abstract

Wheat (Triticum aestivum L.) grain is a contributing source of dietary Cd in New Zealand, but despite this, there is a dearth of information on Cd concentrations in wheat and the factors that affect uptake. We measured Cd concentrations in 12 wheat cultivars grown in field sites across New Zealand and also assessed the soil, plant, and crop factors that have been reported to affect Cd uptake. We found there was a wide range in grain Cd concentrations (0.004 to 0.205 mg kg−1 fresh weight [FW]). The overall mean concentration (0.066 mg kg−1 FW) was below the maximum limit (ML) of 0.1 mg kg−1 FW. Only 7% of grain samples across seven sites exceeded the ML. There were significant (P < 0.05) differences (2.5‐fold) in Cd concentrations in wheat grain between cultivars. No strong significant relationships were found between soil properties and Cd concentrations in grain. Further, management factors affecting grain Cd concentrations were inconsistent. Given the lack of relationships between soils and management practices, the most effective way of limiting Cd uptake in wheat grain at sites where Cd exceeds MLs may be the use of low‐Cd‐accumulating cultivars. Further studies are required to explore specifically the influence of irrigation and effects of type and rate of fertilizer on Cd uptake in wheat, as well as to better understand the mechanisms of Cd uptake in wheat. Core Ideas There was a 2.5‐fold range in Cd concentrations in grain among cultivars. No relationships were found between soil properties and Cd in grain. Overall Cd concentrations in wheat grain were below maximum limits. Using low‐Cd‐accumulating cultivars may be a strategy to limit uptake in grain.

Reduced root mycorrhizal colonization as affected by phosphorus fertilization is responsible for high cadmium accumulation in wheat

“…There are several soil and crop management factors that also have a significant impact on solubility of Cd in soil and root uptake such as soil pH, cropping systems, liming, soil salinity, phytoavailability of Zn in soil, the levels of nitrogen and P fertilization and plant genotype (Mench 1998;Sheppard et al 2009;McLaughlin et al 2021). It is commonly observed that the soil Cd concentration shows a poor association with the plant Cd concentration in several crops such as wheat, potato and rice (McLaughlin et al 1997;Li and Zhou 2019;Gray et al 2019).…”

Implications of wheat farming in Cd(II) and Pb(II) contaminated red eutrophic Oxisol: an experimental pilot investigation

“…The accumulation of Cd in grains (mean of 0.92 mg kg À1 ) was evidence that when wheat grew exposed to half the permitted values (1.5 mg kg À1 ), it did not result in toxic effects on plants; however, grains could have toxic levels of Cd for animals and humans. Furthermore, Gray et al (2019) evidence that variations in Cd uptake capacity might be observed depending on the wheat cultivars. Also, differential Cd uptake capacity among the wheat cultivars causes differences in Cd accumulation in wheat derivates, i.e., flour, consequently presenting Cd levels that disagree with national standards.…”

“…Wheat cultivation on soils contaminated with Cd and Pb is well-reported: Gray et al (2019) studied the effects of the cultivar type, soil properties, and crop management in New Zealand-contaminated soils. Wu et al (2020) observed Pb uptake to grains, making predictions for the translocation of Pb for different wheat organs in different types of China soils.…”

Bioaccumulation and Tolerance Indices of Cadmium in Wheat Plants Grown in Cadmium-Spiked Soil: Health Risk Assessment

“…The concentrations of Cd in cultivated soils ranged from 0.11 to 6.37 mg kg −1 , whereas in the background soil it ranged from 0.02 to 1.99 mg kg −1 in the Sydney region (Gray et al, 2019). The ANZ environmental investigation guideline for soil Cd is 3 mg kg −1 (Siddique et al, 2021).…”

“…Ecological urban soil investigation level is 3 mg kg −1 although background Cd in soil is 1 mg kg −1 (Kandic et al, 2019). Moreover, wheat grain Cd concentrations exceed the Australian and New Zealand food standards for Cd when it is grown in soil with 0.6 mg Cd kg −1 soil (Gray et al, 2019). The low-Cd accumulating wheat cultivars with high macro-and micro-nutrients contents in plant biomass are the best way to diminish Cd concentration in wheat grain.…”