Soil Quality Assessment after 25 Years of Sewage Sludge vs. Mineral Fertilization in a Calcareous Soil

Ana Simoes-Mota, Rosa Maria Poch, Alberto Enrique, Luis Orcaray and Iñigo Virto
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Ana Simoes-Mota: Departamento Ciencias, IS-FOOD, Universidad Pública de Navarra, 31006 Pamplona, Spain
Rosa Maria Poch: Departament de Medi Ambient i Ciències del Sòl, ETSEA, Universitat de Lleida, 25198 Lleida, Spain
Alberto Enrique: Departamento Ciencias, IS-FOOD, Universidad Pública de Navarra, 31006 Pamplona, Spain
Luis Orcaray: Área de Innovación, Sección de Sistemas Sostenibles, Instituto Navarro de Tecnologías e Infraestructuras Agroalimentarias, 31610 Villava, Spain
Iñigo Virto: Departamento Ciencias, IS-FOOD, Universidad Pública de Navarra, 31006 Pamplona, Spain

Land, 2021, vol. 10, issue 7, 1-20

Abstract: The aim of this work was to identify the most sensitive soil quality indicators and assess soil quality after long-term application of sewage sludge (SS) and conventional mineral fertilization for rainfed cereal production in a sub-humid Mediterranean calcareous soil. The treatments included six combinations of SS at different doses (40 t ha −1 and 80 ha −1 ) and frequencies (every 1, 2 and 4 years), plus a control with mineral fertilization, and a baseline control without fertilization. Twenty-five years after the onset of the experiment, 37 pre-selected physical, chemical and biological soil parameters were measured, and a minimum data set was determined. Among these indicators, those significantly affected by treatment and depth were selected as sensitive. A principal component analysis (PCA) was then performed for each studied depth. At 0–15 cm, PCA identified three factors (F1, F2 and F3), and at 15–30 cm, two factors (F4 and F5) that explained 71.5% and 67.4% of the variation, respectively, in the soil parameters. The most sensitive indicators (those with the highest correlation within each factor) were related to nutrients (P and N), organic matter, and trace metals (F1 and F4), microporosity (F2), earthworm activity (F3), and exchangeable cations (F5). Only F3 correlated significantly (and negatively) with yield. From these results, we concluded that soil quality can be affected in opposite directions by SS application, and that a holistic approach is needed to better assess soil functioning under SS fertilization in this type of agrosystem.

Keywords: soil quality assessment; sewage sludge; long-term effect; Mediterranean soils (search for similar items in EconPapers)
JEL-codes: Q15 Q2 Q24 Q28 Q5 R14 R52 (search for similar items in EconPapers)
Date: 2021
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