Toxicity of Laundry Sludge to Corn Plants.

The textile sludge is an important source of soil and water pollution in the northwestern region of Paraná state-Brazil. This sludge is loaded with organic matter, chemical essential elements to plants and heavy metals. 13 textiles sludges were characterized by total chemical analysis and nutrients availability to corn plants. In order to evaluate the suitability of these sludges as soil conditioners and source of nutrients, two green house experiments were set up using corn as testing plant. In the first experiment, corn dry matter production after 30 days of cultivation showed that the sludges could be separated in 3 groups. One the sludges is biologically treated (CLI) and the other are treated by a physico-chemical process (Scalon and Nova Maringá). The total chemical analysis showed high content of carbon, phosphorus, electric conductivity, titanium, iron and manganese concentrations in the sludges. A second green house experiment was run with the three sludges applied in different doses (0 to 40 t ha^-1, dry matter basis) in a Dark Red Latosol (Haplorthox) previously limed and fertilized. After 120 days, roots, shoots and corn grain production could be evaluated by regression analysis. Maximum doses varied from 20-30 t ha^-1 for the physico-chemical treated sludges and over 40 t ha^-1 for the biologically treated one. The higher concentration of extractable Al³⁺, associated to a phosphorus and potassium deficiency were the main reasons to the difference in dry matter and grain production among the three sludges.