Screening for phyto‐toxic contaminants in an industrial source of nutrients intended for foliar and root fertilization

Abstract

Plant screening assays were used to determine whether significant levels of growth inhibitory and phytotoxic contaminants were present in a new industrial source of potassium dihydrogen phosphate fertilizer intended for foliar and root application. Maize (Zea mays L.) plants hydroponically cultured in a controlled environment chamber, were used for the assays. The threshold concentration of industrial potassium phosphate which just caused burn damage symptoms, when applied as standard droplets to the leaf surface with Tween 80 wetting agent was 0.5M. The comparative threshold concentration for damage by an ultrapure analytical grade of potassium phosphate was >0.6M. Thus, the industrial grade had slightly higher toxicity for leaf application. Effects on plants of supplying industrial and analytical grade phosphates via the roots were also compared. Root and leaf elongation kinetics, mature leaf cell lengths, apparent capacity for leaf cell production, shoot ontogeny, and shoot fresh weight yields were determined at low and high potassium phosphate concentrations. The effects of analytical and industrial grade fertilizer salts were equivalent. We suggest that these rapid and relatively simple plant screening assays can provide a useful safety check, prior to large scale field trails, for fertilizer nutrients produced by new industrial processes.

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