Uptake and partitioning of sludge-borne copper in field-grown maize (Zea mays L.)

Accumulation of sludge-borne copper (Cu) by field-grown maize and its distribution between the different plant organs was studied in detail in a long-term sewage sludge field trial. Since 1974, field plots on a coarse sandy soil have been amended each year with farmyard manure (FYM) at a rate of 10 t dry matter (DM) ha^?1 year^?1 and with sewage sludge at the two levels of 10 t DM ha^?1 year^?1 (SS 10) and 100 t DM ha^?1 per 2 years (SS 100). All field plots have been cropped annually with maize. In 1993, five replicate plants per treatment were examined at six different growth stages from seedling to grain maturity. Each plant was separated into at least 12 different parts and the Cu content of each was determined. Regarding growth parameters, no visible deleterious effects on plant development due to the different soil treatments could be observed, although the dry matter yield of roots and stalks of SS 100-treated plants was significantly reduced. Significantly increased Cu concentrations of up to 60 mg Cu kg^?1 DM in the roots of young SS 100-grown maize plants and of up to 20 mg Cu kg^?1 DM in the upper leaves at silage stage were found. No critical Cu amounts were reached in the grains until harvest.