The effect of crop rotations and tillage practices on cadmium concentration in wheat grain

Abstract

The cadmium concentrations in wheat grain were determined from three crop rotation x tillage experiments in South Australia. Generally, the concentrations in grain were highest in wheat grown after lupins and lowest in wheat grown after cereal. The high cadmium concentrations in grain from wheat/lupins plots could not be explained solely by acidification, thus indicating involvement of other processes in cadmium availability. While cadmium concentration in grain also increased with increasing rates of nitrogenous fertilizers, the results of cultivation practices were generally too inconsistent to allow conclusions to be drawn. Cadmium concentrations exceed the maximum permissible concentration (MPC) of 0.05 mg kg-1 set by the National Health and Medical Research Council (NHWIRC) for unspecified foods in only one of the three tillage experiments. This study indicates that crop rotation is an important factor affecting cadmium uptake. Under certain soil conditions and with particular wheat varieties, the cadmium concentration in grain may exceed the MPC as the result of the crop rotation used.

Effects of zinc activity in nutrient solution on uptake, translocation, and root export of cadmium and zinc in three wheat genotypes with different zinc efficiencies

“…Our results suggest that the Cd uptake system in Zn-efficient genotypes is different from that in the Zn-inefficient genotypes (Oliver et al 1995;Hart et al 1998). The nature of Cd uptake saturability may be different among wheat genotypes.…”

Cadmium accumulation in crops

“…Cadmium concentration in wheat grain was higher when grown in rotation after lupins than after cereals (Oliver et al 1993). The increase in Cd concentration may be partially, but not solely, attributed to the acidifying effect of the legume and the subsequent mobilization of Cd for uptake by the subsequent crop.…”

“…Although cultivation practices did not consistently influence Cd concentration in wheat in studies conducted by Oliver et al (1993), there was a tendency towards higher concentrations of Cd in crops grown under direct drilling into stubble. The authors suggested that restricted rooting under zero tillage could encourage uptake of Cd from the surface soil horizons, where concentration of Cd is higher than at lower soil depths due to a long history of application of high Cd fertilizers.…”

“…The authors suggested that restricted rooting under zero tillage could encourage uptake of Cd from the surface soil horizons, where concentration of Cd is higher than at lower soil depths due to a long history of application of high Cd fertilizers. Preferential uptake of Cd from undisturbed acidified zones associated with lupin roots was also suggested as a possible reason for higher Cd uptake under zero tillage (Oliver et al 1993). …”

“…NITROGEN. Nitrogen fertilizers can increase Cd concentration in plants, although the fertilizer does not normally contain significant levels of Cd (Table 5) (Andersson 1976;Oliver et al 1993;Grant et al 1996). The increased plant uptake of Cd with N application may be due to increases in osmotic strength of the soil solution, ion exchange reactions, or soil acidification.…”