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BACKGROUND Cadmium (Cd) is a mobile heavy metal and soybeans accumulate more of this element compared to other grain crops. Because vegan and vegetarian lifestyles are increasingly popular, plant‐based diets should be free from contaminants. Cd minimization has recently been identified as a breeding aim in addition to protein and oil levels. It is also important to consider the regional variability of Cd in crops. RESULTS: A large sample collection (n = 602) was subjected to Cd analyses. Soybeans were grown using a standard protocol by private gardeners in a citizen science program. Some 12.5% of samples exceeded European Union limits, although Cd concentrations and exceedances showed regional variation around the national mean (0.13 mg kg−1). Contamination was higher in densely populated regions, possibly as a result of the long‐term emissions of heavy metal loaded dusts from industry, traffic and energy production. Cd concentrations were also elevated in regions once characterized by mining and heavy industry. Values were low overall in rural areas and agricultural regions despite potential inputs via phosphate fertilizers. CONCLUSION: Grain Cd levels are highly variable across Germany. Soybean farming may be problematic in regions with a long history of mining and heavy metal deposition. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Rising CO2 concentrations associated with drought stress is likely to influence not only aboveground growth, but also belowground plant processes. Little is known about root exudation being influenced by elements of climate change. Therefore, this study wanted to clarify whether barley root exudation responds to drought and CO2 enrichment and whether this reaction differs between an old and a recently released malting barley cultivar. Barley plants were grown in pots filled with sand in controlled climate chambers at ambient (380 ppm) or elevated (550 ppm) atmospheric [ CO2] and a normal or reduced water supply. Root exudation patterns were examined at the stem elongation growth stage and when the inflorescences emerged. At both dates, root exudates were analyzed for different compounds such as total free amino acids, proline, potassium, and some phytohormones. Elevated [ CO2] decreased the concentrations in root exudates of some compounds such as total free amino acids, proline, and abscisic acid. Moreover, reduced water supply increased proline, potassium, electric conductivity, and hormone concentrations. In general, the modern cultivar showed higher concentrations of proline and abscisic acid than the old one, but the cultivars responded differentially under elevated CO2. Plant developmental stage had also an impact on the root exudation patterns of barley. Generally, we observed significant effects of CO2 enrichment, watering levels, and, to a lesser extent, cultivar on root exudation. However, we did not find any mitigation of the adverse effects of drought by elevated CO2. Understanding the multitude of relationships within the rhizosphere is an important aspect that has to be taken into consideration in the context of crop performance and carbon balance under conditions of climate change. [ABSTRACT FROM AUTHOR]