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(70-68) Prediction of Cd concentrations in wheat grain using simple soil and crop data. McGrath, Steve*,1, Adams, Martin1, Zhao, Fangjie1, 1 Agriculture and Environment Division, Harpenden, UK ABSTRACT- Currently, regulations regarding the maximum permitted concentrations of metals in soils are based on measurements of total, rather than the bioavailable concentrations. However, these need to be modified by the factors affecting bioavailability in different soils. Paired soil and winter wheat samples were taken at 163 representative UK cereal growing sites during 1998 (n = 34), 1999 (n = 61) and 2000 (n = 68) harvest periods. Soils were analysed for pH (water), total cadmium, organic matter, Al, Fe and Mn oxides and wheat grain for Cd. Multiple linear regression analysis was used to identify significant soil variables that could be used to fit a model describing grain cadmium uptake based on the experimental data collected. There was no statistical difference between wheat grain Cd in the three years, so data all (n = 163) were pooled for modelling. Soil pH and total soil cadmium together resulted in a highly significant model (P<0.001) that explained 50% of the variation in grain concentrations with log grain cadmium (mg/kg) = 0.282 + 0.44 log soil cadmium (mg/kg) - 0.1834 soil pH. Cultivar effects on wheat cadmium concentrations were found to be significant (P<0.05) by ANOVA and incorporation of a cultivar term into the model resulted in an improved fit to the observed data, increasing the percentage variation accounted for to 56%. Proposed EU limits for metals added to soil in sewage sludges are based on total soil Cd and pH. This model is based on field data and can be used, for example, to test whether the proposed new EU limits for sewage sludge Cd additions to soils are likely to generate grain which exceeds the 2001 EU Regulation (0.2 mg/kg fresh weight) for the maximum Cd concentration in wheat grain. Key words: cadmium, bioavailability, modelling, food, prediction |
