Chemical and microbiological attributes of an oxisol treated with successive applications of sewage sludge¹

Abstract

SUMMARYStudies on sewage sludge (SS) have confirmed the possibilities of using this waste as fertilizer and/or soil conditioner in crop production areas. Despite restrictions with regard to the levels of potentially toxic elements (PTE) and pathogens, it is believed that properly treated SS with low PTE levels, applied to soil at adequate rates, may improve the soil chemical and microbiological properties. This study consisted of a long-term field experiment conducted on a Typic Haplorthox (eutroferric Red Latosol) treated with SS for seven successive years for maize production, to evaluate changes in the soil chemical and microbiological properties. The treatments consisted of two SS rates (single and double dose of the crop N requirement) and a mineral fertilizer treatment. Soil was sampled in the 0-0.20 m layer and analyzed for chemical properties (organic C, pH, P, K, Ca, Mg, CEC, B, Cu, Fe, Mn, Zn, Cd, Ni, and Pb) and microbiological properties (basal respiration, microbial biomass activity, microbial biomass C, metabolic quotient, microbial quotient, and protease and dehydrogenase enzyme activities). Successive SS applications to soil increased the macro-and micronutrient availability, but the highest SS dose reduced the soil pH significantly, indicating a need for periodic corrections. The SS treatments also affected soil microbial activity and biomass negatively. There were no significant differences among treatments for maize grain yield. After seven annual applications of the recommended sludge rate, the heavy metal levels in the soil had not reached toxic levels.Index terms: municipal waste, organic matter, soil microbes, maize. (C-orgânico, pH, P, K, Ca, Mg, CTC, B, Cu, Fe, Mn, Zn, Cd, Ni e Pb)

Yield and nutrition of sunflower fertilized with sewage sludge stabilized by different processes

“…Several authors consider the sludge residue as low-K, as it is found predominantly in the ionic form, which tends to remain in solution during the process of wastewater treatment, and chemical complementation with this element is constantly recommended (Bueno et al, 2011;Guedes et al, 2006;Simonete et al, 2003). However, in the present study, K could not be considered a limiting element of productivity, because the quantities added into the soil by the treatments solarized, composted, vermicomposted and limed were, respectively: 0.7, 4.2, 3, 1 and 8.9 times the recommended.…”

Soil chemical alterations of a Dystroferric Red Latosol (Oxisol) treated with an alkaline effluent from a pharmaceutical industry

“…The optimal Ca:Mg ratio may be variable according to the crops. Bueno et al (2011) mentioned that the ideal ratio may range, but generally, the authors consider a Ca:Mg ratio in the range of 3:1 or 4:1 to be optimal because these ratios are found in most naturally highly fertile soils. Thus, significant changes, like those observed in this research, may compromise the nutrient balance of the soil and consequently hinder plant development.…”

Solução do Solo e Análise de Componentes Principais para Monitoramento da Aplicação de Lodo de Esgoto

“…Diversos trabalhos demonstraram os efeitos benéficos do lodo nas propriedades físicas, químicas e biológicas do solo (Simonete et al, 2003;De Maria et al, 2007;Bueno et al, 2011), com reflexos na nutrição das culturas e, consequentemente, na produtividade.…”