Effect of soil chloride level on cadmium concentration in sunflower kernels

Abstract

Understanding soil factors related to cadmium (Cd) uptake and accumulation in plants is important for development of agronomic technologies, and breeding strategy to produce low Cd crops. The objective of the study was to examine the effect of soluble salts (chloride and sulfate) and other soil factors on the Cd concentration in sunflower (Helianthus annuus L.) kernels. Commercial nonoilseed hybrid kernels and soils were sampled from 22 farmer's production fields in North Dakota and Minnesota. The sites sampled included saline and nonsaline variants from 7 soil series. Soils were sampled at four depths. Relationships between kernel Cd level and soil physical and chemical characteristics were examined. The soil pH covered a narrow range (7.3–8.1) at these sampled sites. Regression analysis showed that there was no correlation between kernel Cd and soil pH at any depth. The kernel Cd level was highly correlated with DTPA-extractable Cd in all 4 depths, and with clay content in sub-soils. Soil chloride and sulfate concentrations varied among soil series and within soil series. The absence of a statistically significant effect of soil sulfate level on kernel Cd concentration, indicated that soil sulfate levels did not affect Cd uptake by sunflower plants. However, soil chloride levels in sub-soil were correlated with kernel Cd. The most important soil factor was DTPA-extractable Cd. When chloride was included in the multiple regression equations, R square (R2) values improved significantly. These results demonstrate that soil chloride concentration is another important factor related to Cd uptake in sunflower plants.