Resumo O objetivo deste trabalho foi caracterizar a macrofauna edáfica em sistemas de produção de grãos sob plantio direto e convencional no Sudoeste do Piauí, na região de Matopiba. Amostras de solo foram coletadas nas camadas de 0,0-0,1, 0,1-0,2 e 0,2-0,3 m, com serrapilheira, em áreas cultivadas predominantemente com milho e soja, sob preparo convencional e plantio direto, em solos com diferentes texturas. Remanescentes de vegetação nativa adjacentes foram amostrados como referência. A macrofauna edáfica nos diferentes sistemas de uso do solo foi identificada até o nível de famílias, as quais foram agrupadas de acordo com suas funções ecológicas. Os grupos mais abundantes nas áreas amostradas foram Isoptera, Hymenoptera e Coleoptera, este com o maior número de famílias. A análise de componentes principais revelou que os grupos funcionais geófago/bioturbador, fitófago/praga e predador/parasita estão associados a solos de textura argilo-siltosa; enquanto o grupo detritívoro/decompositor, a solos mais arenosos. Os sistemas de manejo do solo alteram a estrutura da comunidade de macroinvertebrados edáficos em relação à condição natural de Cerrado. O plantio direto proporciona maior abundância e riqueza de espécies que o preparo convencional, e minimiza o impacto de sistemas agrícolas sobre a biodiversidade da macrofauna edáfica.

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The aim of this study was to characterize the soil macrofauna under different crop systems and compare them to the macrofauna under the native vegetation of a Cerrado/Caatinga ecotone in southwestern Piauí State, Brazil. The areas studied included areas under sweetsop cultivation (Annona squamosa L.), andropogon grass with three years of use, andropogon grass with six years of use, pivot-irrigated corn, Napier grass, and native vegetation. In each area, soil layers of 0-0.1, 0.1-0.2, and 0.2-0.3m, including the surface litter, were evaluated following the Tropical Soil Biology and Fertility Program (TSBF) recommendations. The soil macrofauna from the different land-use systems were identified to the family level, and the mean density of each taxon was calculated for each soil-management type and layer. The structure of the soil macrofauna was negatively altered under the different crops in comparison to the native Cerrado/Caatinga vegetation, with macrofaunal occurrence varying in the different soil layers. A correlation existed between the functional groups and the soil grain-size distribution and moisture. Napier grass cultivation favored greater soil macrofaunal abundance, with a predominance of families belonging to the orders Isoptera and Hymenoptera. Number of soil macrofaunal families under pivot-irrigated corn was more like the number observed with the native vegetation, and corn also had greater family diversity compared to the other crops studied. Therefore, pivot-irrigated corn can reduce the impact of anthropogenic land use on the diversity of soil macrofauna.

Soil quality is essential for maintaining the sustainability of agro-ecosystems and ecosystem services provided by this natural resource. The present study aimed to assess the physical quality of soil through the characterization of the physical properties in grain production systems in the Southwest region of Piauí State, Brazil. The study was carried out in the Cerrado region of Piauí in four cities in areas of expansion of the agricultural frontier of the state: Baixa Grande do Ribeiro, Sebastião Leal, Uruçuí and Bom Jesus. Soil samples were collected in April 2012, in areas of grain production under conventional and no-tillage systems. Adjacent areas with native vegetation were also sampled as reference. Bulk density, effective saturation, hydraulic conductivity, penetration resistance, porosity and aggregation were measured. Regardless of the type of soil management used, agricultural systems degrade soil physical quality. No-tillage showed higher bulk density, penetration resistance and aggregation, with lower total porosity, macroporosity and hydraulic conductivity. The physical quality of soil in the agricultural areas of the Cerrado region of Piauí was dependent on the soil texture, while silt, clay and organic matter were determinant for soil aggregation, mechanical resistance, total porosity and microporosity.