Soybean as affected by high concentrations of arsenic and fluoride in irrigation water in controlled conditions

• The effects of arsenic and fluoride in irrigation water on soybean were studied.
• The experiment mimics sprinkler irrigation.
• Arsenic was much more phytotoxic than fluoride.
• The toxic effect of both elements was additive.
• The concentration of both elements in beans was generally low.

Arsenic (As) and Fluoride (F) are both present in many groundwater sources around the world. The use of these waters for irrigation purposes could cause problems on crop production and the food chain. The aim of this work was to investigate soybean biomass production, bean yield and As and F accumulation in the soil and the plant in controlled conditions. An experiment mimicking sprinkler irrigation with water enriched in As and F, applied individually or simultaneously was carried out. When irrigation was applied, part of the water fell inside the pot, either directly or through the leaves and increased the contents of bioavailable As and F forms in the soil. Arsenic was more toxic to soybean than F. Significant biomass and yield reductions, and As and/or F accumulation in plant tissues where observed when As and F concentration surpassed 0.6 mg As L−1 and 25 mg F L−1. When As and F were applied simultaneously the toxic effect were additive and the detrimental effects were larger. Soybean bean yield was reduced almost 50% for As and 30% for F. Arsenic and F concentration increased in all organs but soybean beans presented lower values than concentrations hazardous to human and animal health. Bean concentrations were less than 1 mg As kg−1 and less than 5 mg F kg−1.