Abstract
The application of sewage sludge is a concern because it may affect the quality of organic matter and microbiological and biochemical soil properties. The effects of surface application of sewage sludge to an agricultural soil (at 18 and 36 t ha-1 dry basis) were assessed in one maize (Zea mays L.) growing season. The study evaluated microbial biomass, basal respiration and selected enzymatic activities (catalase, urease, acid and alkaline phosphatase, and β-glucosidase) 230 days after sewage sludge application and infrared spectroscopy was used to assess the quality of dissolved organic matter and humic acids. Sewage sludge applications increased the band intensity assigned to polysaccharides, carboxylic acids, amides and lignin groups in the soil. The organic matter from the sewage sludge had a significant influence on the soil microbial biomass; nevertheless, at the end of the experiment the equilibrium of the soil microbial biomass (defined as microbial metabolic quotient, qCO2) was recovered. Soil urease, acid and alkaline phosphatase activity were strongly influenced by sewage sludge applications.
Highlights
Soil organic matter (SOM) is generally recognized as one of most important factors of soil fertility, crop production, and protection from soil degradation, erosion and desertification (Senesi et al, 2007)
According to the maximum permitted amounts of heavy metals for final disposal of sewage sludge and biosolids, as established in the Mexican regulation (NOM-004Semarnat-2002), the SS tested in this experiment was classified as an excellent amendment for agricultural use
There are reports in the literature that sewage sludge added to soil raised the OM, P and N contents (Vaca et al, 2006; Dias et al, 2009)
Summary
Soil organic matter (SOM) is generally recognized as one of most important factors of soil fertility, crop production, and protection from soil degradation, erosion and desertification (Senesi et al, 2007). Most physical and chemical soil properties and processes, including the SOM decomposition, nutrient availability, the synthesis of humic acids (HAs), and the interactions of HAs with inorganic soil components and inorganic and organic pollutants can be modified by the addition of SS to soil (García-Gil et al, 2004). In this context, a number of biological and biochemical properties can be used as early and sensitive indicators of SOM transformations and dynamics, and of stress and recovery conditions in the soil (Dick & Tabatabai, 1993)
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