WIT Press

Sewage Sludge Effects On Biological And Biochemical Parameters In A Degraded Soil


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J C García-Gil, C Plaza & A Polo


Sewage sludge were applied to degraded soils cropped with barley at the municipal district of Pinto (Madrid, Spain). Soil samples were analyzed at the end of the yield to determine the residual effects of sludge applications at a rate of 40 t ha-’ on soil respiration, microbial biomass carbon, and enzyme activities involved in biogeochemical cycles of nutrients. The addition of organic matter with this residue caused changes in soils biological parameters, provoking an increase in soil microbial biomass and basal respiration, improving the potential microorganism activities. Biochemical parameters such as oxidoreductase and hydrolase enzymes were studied. Activities of both groups of enzymes showed an increase with the organic treatment. These effects showed an improvement in soil quality that was only significant in soils that received the organic treatment more recently, meanwhile the residual effects on these parameters three years after its application were very similar to the unamended soils, as a consequence of intensive mineralization processes under the environmental conditions in the studied area. 1 Introduction The intensive cropping of the world’s agricultural land has caused disturbances in the soil’s physical, chemical and biological properties, which can cause changes in C cycling, resulting in significant losses of soil organic matter and drastic changes in nutrient fluxes [l]. One of the characteristics of soils in Mediterranean countries is their low organic matter content. The decrease in soil organic matter is paralleled by declines in soil fertility, as many authors have demonstrated [2, 3]. One alternative to reverse these degradative processes in soil quality is the addition of organic matter [4, 5].