Physical-hydric attributes in Latossolo Amarelo under systems of use in the Cerrado/Caatinga ecotone areas in Piauí State, Brazil.

The Cerrado/Caatinga transition region in Piauí State has a high potential for production of food, fiber and energy, representing about 19% of the total area of the State. This work aimed to evaluate physical and hydraulic attributes under different crops in Latossolo Amarelo Distrófico (Oxisol) in cerrado/caatinga transition areas, in the Southwest of Piauí. In this study five areas with different crops were evaluated as follows: areas under pasture crop with Andropogon gayanus grass with three and six years of crop, area under intensive crop of Pennisetum purpureum grass, area under orchard of Annona squamosa L., area under intensive crop irrigated with central pivot and area under native vegetation of cerrado/caatinga ecotone representing a condition of equilibrium. Soil attributes evaluated were: soil density, total porosity, macroporosity, microporosity, unsaturated pores, blocked pores, saturation humidity, effective saturation, water readily available, void index, mechanical resistance of soil and saturated field hydraulic conductivity. The intensive crop of napier grass for five consecutive years and the pivot irrigated area under intensive crop for four years presented the greatest negative impacts on soil density, total porosity, macroporosity, saturation humidity, effective saturation, water readily available and index of voids.

Soil Physical Quality in Agricultural Systems on the Cerrado of Piauí State, Brazil.

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.