Cadmium status of soils, plants, and grazing animals in New Zealand

Abstract

Abstract The accumulation of cadmium (Cd), a biotoxic heavy metal, in the food chain is undesirable. A national survey of soils and plants and random testing of kidneys from grazing animals slaughtered for export was conducted to assess Cd accumulation in New Zealand (NZ) pastoral agriculture. Average total Cd content of pastoral soils (0–7.5 cm) was 0.44 (Xg Cd/g compared to 0.20 |xg Cd/g for “native” (non‐agricultural) soils. Total soil Cd was highly correlated to total soil P. An increase in total soil P is a reflection of fertiliser history thus phosphatic fertiliser use is implicated in Cd accumulation in pastoral soils. The elevated pastoral soil Cd levels were not clearly reflected in grass or legume species but were displayed in weed species viz, 0.28 ug Cd/g c.f. 0.14 μg Cd/g for pastoral and native sites respectively. Over the period 1988–91, 22–28% of sheep and 14–20% of cattle kidneys sampled exceeded the NZ maximum residue level of 1 μg Cd/g. Kidney Cd content was highly age‐related. Cadmium was also present in feral deer and feral sheep kidneys showing that Cd occurs naturally in the environment.