Thursday, 13 July 2006

The Application of Pulp Industry Sludge to Two Degraded Soils of the IX Region and Its Impact to Some Physical Properties of the Soil.

Felipe O. Gallardo, Universidad de La Frontera, Avenida Francisco Salazar 01145, Temuco, 56, Chile

The pulp fabrication process generates large quantities of solid residues (sludge), that accumulate inside the industry, which provokes economic and environmental concern. There has been an interest of discovering reutilization options and therefore to diminish the volume of these residues. A great part of the Organic Matter (OM) from chemical and microbiological sources concentrates in the residues. The content and characteristics of the residue are responsible of the major part of the physical processes of the soil. Poor agronomic management and natural processes such as erosion can cause degradation of volcanic soils, that has decreased the content and the quality of the soil organic matter. The research was conducted with an experimental design of completely random treatments (11) involving four levels of residue in Gorbea and Collipulli soils and three controls (Temuco, Gorbea and Collipulli soils) with three repetitions. It also included five steps of evaluation (0, 15, 30, 45, 60 days) for each soil. The degraded soils derived from volcanic ash were applied with the residue and subsequently the effects of the application to the physical properties of the soil were evaluated characterizing first the physical aspects of the residue (humidity) and secondly of the degraded soils (Gorbea, Collipulli and Temuco): humidity, soil water holding capacity, density bulk, density real, porosity, stability of aggregates and texture. These evaluated parameters increased with the applied dose of residue (0,15, 20, 30 and 50 Mg ha-1) in the Gorbea soil. The first sample was drawn after 15 days of stabilization of the soil-residue –mixture. In the first sample, the stability of aggregates, without application of the residue, was 58.4 % and with the 50 Mg ha-1 dose was 82.5 % presenting a significant variation. The evaluation periods did not show any significant variation; the stability of aggregates increased to 84.9 % using the same dose at day 30. In addition, the parameters of the Collipulli soil were not found to have significant effect due to the poor quality of its structure. Despite that the majority of the analyzed parameters of the evaluated soils, Gorbea, Collipulli and Temuco, were not found to be significant, they still increased with the applied residue. This indicates that the residues benefit these soils by increasing the organic matter. In addition, it can be concluded that the residue of the cellulose is an alternative remediation method for degraded soils, improving the physical properties over time and permitting a better cultivation of plants. However, it is important to control the methods, the application time and the properties of the residue and soil.

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