Changes in chemical attributes of soil treated with tannery sludge in Amazonia

Application of residuals to soil can favor the development of nutrient-poor agricultural areas. The objective of this study was to evaluate changes in the chemical attributes of soil after application of tannery sludge. The applied treatments were 1) Mineral control: 100 kg N ha-1, applied in different stages (25% at planting and 75% when plant maize was in the 1.4 development stage); 2) tannery sludge: 50 kg ha ֿ¹; 100 kg ha¹; 200 kg ha ֿ¹; 400 kg ha ֿ¹; and 600 kg ha ֿ¹ of organic-N. All plots were treated with fertilizer (75 kg ha ֿ¹ P2O5 and 50 kg ha ֿ¹ K2O). In the mineral control, nitrogen was applied in ammonium sulphate form. Soil samples were analyzed to determinate pH, calcium, magnesium and aluminum in 1M KCl solution, potential acidity (hydrogen + aluminum in a calcium acetate solution pH 7), and potassium and sodium in a Mehlich 1 solution. The application of tannery sludge modified the chemical attributes of the soil, increasing pH and Na+, Ca+2, and Mg+2 contents.