Sodium-affected alfisols of the agreste region, state of Paraíba, Brazil, as known by potter-farmers and agronomists

Decisions and practical attitudes of land use and management adopted by rural populations are, to a great extent, based on local soil knowledge. This study was performed to describe and analyze chemical, physical and morphological characteristics of sodium-affected Alfisols employed in traditional pottery; and to compare, through statistical analysis, pedogenetical horizons and soil layers, as recognized in soil profiles by professional researchers and potter-farmers, respectively. Fieldwork was performed in Chã da Pia, a rural village in the municipality of Areia, in the Agreste region of the State of Paraíba, Northeast Brazil. Ethnoscientific techniques were used to describe and analyze soil knowledge of potter-farmers who played the role of informants. A comparison of soil categories recognized by farmers and researchers was performed through discriminant-canonical analysis. Soils from which local people obtain a material named "barro de loiça" (pottery clay) were classified as Typic Natraqualf and Vertic Albaqualf, according to Soil Taxonomy. Potter-farmers were able to identify differences between the tillable topsoil and underlying layers from which they extract ceramic clay. Some soil layers, recognized by potter-farmers, were similar to pedogenetic horizons of the same soils, recognized by researchers, in terms of physical, chemical and morphological characteristics. Discriminant-canonical analysis was a useful tool to articulate and compare information related to soil knowledge held by distinct social groups