Chemical and Biochemical Properties of Oxisols after Sewage Sludge Aplication for 16 Years

Abstract

The large production of sewage sludge (SS), especially in large urban centers, has led to the suggestion of using this waste as fertilizer in agriculture. The economic viability of this action is great and contributes to improve the environment by cycling the nutrients present in this waste, including high contents of organic matter and plant nutrients. This study evaluated the chemical and biochemical properties of Dystrophic and Eutroferric Latossolos Vermelhos (Oxisols) under corn and after SS application at different rates for 16 years. The field experiment was carried out in Jaboticabal, Sao Paulo State, Brazil, using a randomized block design with four treatments and five replications. Treatments consisted of control - T1 (mineral fertilization, without SS application), 5 Mg ha(-1) SS - T2, 10 Mg ha(-1) SS - T3, and 20 Mg ha(-1) SS - T4 (dry weight base). The data were submitted to variance analysis and means were compared by the Duncan test at 5 %. Sewage sludge increased P extracted by resin in both the Latossolos Vermelhos, Dystrophic and Eutroferric, and the organic matter content in the Dystrophic Latossolo Vermelho. The waste at the rate 20 Mg ha(-1) on a dry weight basis promoted increases in acid phosphatase activity in Eutroferric Latossolo Vermelho, basal respiration and metabolic quotient in Dystrophic Latossolo Vermelho. The rate 20 Mg ha(-1) sewage sludge on a dry weight basis did not alter the soil microbial biomass in both the Latossolos Vermelhos; in addition, it improved corn yields without inducing any symptoms of phytotoxicity or nutrient deficiency in the plants.