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Las plantas de tratamientos de aguas residuales (PTAR) generan diariamente toneladas de lodos (biosólidos), los cuales pueden tener un uso agrícola como fuente de nutrientes y material mejorador del suelo, aunque también pueden ser fuente de contaminación por metales pesados y sales solubles. En este estudio se evaluó, en un suelo representativo de la zona de influencia de la PTAR de la ciudad de Aguascalientes, México, la aplicación de biosólidos y el efecto de su contenido de metales pesados y sales solubles en el suelo y plantas de pasto ballico, con la finalidad de establecer su aprovechamiento agrícola sin riesgo potencial de degradación y contaminación de suelos y plantas. Se hizo una caracterización química de los biosólidos y los suelos estudiados. Los biosólidos presentaron pH ligeramente ácido, alto contenido en sales solubles y concentración de metales pesados dentro de los límites máximos permisibles según la NOM-004-SEMARNAT-2002, por lo que se les puede dar uso agrícola. Dosis crecientes de biosólidos incorporados al suelo no presentaron efectos en éste, en cuanto a acumulación de metales pesados, pero sí se incrementó el contenido de sales solubles, y con dosis superiores a 80 t·ha-1 se llegó a niveles que pueden reducir el rendimiento de la mayoría de cultivos.

Background: Hñahñu (Otomi) farmers organize their experiences and ecological learning into a farmland system designed to grow food in areas of scarce water and low soil fertility. The purpose of this paper is to examine Hñahñu concepts and categories pertaining to the farming landscape and the ecological foundations underlying the system, its management implications, and categorial organization in Huitexcalco de Morelos, Mezquital Valley, Mexico., Methods: Native terms and their links to landscape were recorded and discussed in various workshops. Open interviews and field trips with local experts were used to explain soil and water management practices that allow Hñahñu farmers to maintain sustained yields throughout the year. We then used participatory mapping in order to explore the semantic relations of the terms with the space and its validity in the productive landscape., Results: We elicited 7 Hñahñu language terms related to landforms, 4 related to land use categories, and 17 related to their constituent components organized in two hierarchical levels. We found that mothe as a term of land usage was followed by mothee, ñut'athee, gadñhe, or muiñhe; these primarily refer to the topographic position of the parcel and the form of access to water for irrigation. Stone barriers and earth channels represent the functional structures that are most commonly used by Hñahñu farmers to retain soil and water. In the participatory mapping results, mothe muiñhe displayed a robust spatial link with the gullies. Identifying other landscape categories required a substantial understanding both of management practices of soil and water and forms of organization., Conclusions: This study revealed a complex system of knowledge that contributes to the continued proper management of the local landscape. The terms and their elicited meanings are key to understand the ways in which Hñahñu farmers conceptualize and relate the reality of their landscape and its cultural meanings. Scale and perception were found to have a determining role in defining their taxonomic organization, semantic structure, and relations in space.