SEWAGE-SLUDGE EFFECTS ON CHEMICAL-PROPERTIES OF ACID SOILS

Field experiments were established at two locations (on an Oxisol and an Ultisol) to evaluate the effects of 0, 8, 16, and 24 metric tons ha -1 of aged municipal sewage sludge on soil properties and growth of fo ur crop species. Soil samples taken from each plot, before sludge appl ication and at harvest of the crops, are compared here to determine an y effects of the sludge on pH, exchangeable acidity, exchangeable base s, cation and anion exchange capacity, and extractable phosphorus and trace metals. To test effects on soil properties in a more controlled environment, soil from one site was incubated with the sludge over a p eriod of 4 months. No detrimental effects and several beneficial effec ts were observed. In particular, problems of soil acidity were diminis hed by an increase in pH and exchangeable calcium accompanied by a dec rease in exchangeable acidity. Sludge applications also increased BaCl 2-MgS64 CEC, but only in the Oxisol did the sum of cations increase. D ilute acid-fluoride extractable phosphorus also increased with sludge additions accounting for 2 to 19% of added sludge P for the Ultisol an d 19 to 52% of P added to the Oxisol. Increases in Mehlich-3 extractab le Cu and Zn in the soils were approximately equal to the amounts of t hese elements added to the soil in the sludge.