The effluent from cassava industrial processing presents high ionic organic charge and high nutrient concentration. If discarded indiscriminately in soil, this effluent may cause serious environmental hazard. The objective of this paper is to evaluate changes in physical and chemical attributes of a soil cultivated with lettuce and submitted to increasing doses of cassava wastewater. The experiment was carried out under greenhouse in a completely randomized design with six treatments consisting of application of 0, 5, 15, 25, 45 and 65 m³ ha-1 and five replications. Soil physical (degree of flocculation, dispersed clay in water) and chemical (electrical conductivity of saturation extract of soil, pH, content of P and exchangeable cations K+, Ca2+, Mg2+ and Na+) properties were evaluated for soil characterization. Besides decreasing clay dispersed in water, use of cassava wastewater in the soil increased flocculation degree, pH, electrical conductivity of saturation extract, exchangeable cations and P content. Tendency of soil salinization was observed after cassava wastewater application.
Manihot esculenta; soil fertility; residue use
