The effect of sewage sludge pelletization added at rates of 0, 1 and 5% (v/v) of dry material was studied on corn growth and absorption of Zn, Cu and Ni, with or without the addition of CaCO3 to increase soil pH to 6.0. Three Hapludox soil samples from the State of São Paulo, Brazil, "latossolo roxo", "latossolo vermelho-escuro" e "latossolo vermelho-amarelo" (LR , LE and LV, respectively) were used in a greenhouse experiment conducted in Campinas, State of São Paulo, Brazil, from January to May, 1980. Treatments were placed into plastic bags and, after a 200-day incubation period, were transferred to 2 litter pots in which four corn (Zea mays L.) plants were cultivated in each one. Plant tops were harvested 56 days after emergence, dried, weighted and analysed for Ni, Cu and Zn. Soil samples were taken for DTPA extraction of Ni, Zn and Cu, which were correlated with tissue amounts of these elements by regression analysis. Addition of sewage sludge as pellets significantly decreased corn dry matter production in all soils. Calcium carbonate addition significantly increased dry matter production only in the LE and LV soils, and decreased plant top Zn accumulation when corn was cropped on the LE soil with any kind of sewage sludge. Calcium carbonate addition also did not affect Ni absorption in all soils under investigation. Pelletized sewage sludge addition, which contained 19% less Zn and Ni than the nonpelletized one, decreased the absorption of Zn, Cu and Ni in all soils, except for Ni in the LR. DTPA extraction was more suitable for predicting Zn and Cu availability to corn in the three soils treated or not with CaCO3 and with any kind of sewage sludge applied.
sewage sludge; pelletization; heavy metals; DTPA; liming; corn