Abstract
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.
Highlights
No-till farming (NT) was proposed by the Brazilian government to comply with the country’s voluntary commitment to reduce greenhouse gas (GHG) emissions by 36%
No-till showed higher bulk density (BD) at all the depths investigated when compared to conventional tillage, whose values were closer to the values found in the areas under native vegetation (NV), with means ranging between 1.22 to 1.36 Mg m-3
The average values for bulk density in no-tillage are within the range of 1.36 to 1.72 reported by Silva et al (2014) in the Cerrado of Piauí, while the values obtained for native vegetation and notillage are lower than that obtained by the referred authors
Summary
No-till farming (NT) was proposed by the Brazilian government to comply with the country’s voluntary commitment to reduce greenhouse gas (GHG) emissions by 36%. The goal is to increase the area planted under no-till by eight million hectares until 2020 (Mapa 2012) This goal, which is part of the Low Carbon Agriculture program (ABC in portuguese), is one of the top Brazilian public policies, aimed to mitigate GHG emissions and increase carbon stocks in agricultural soils (Corbeels et al 2016). The Southwest of Piauí is inserted in the region called “Matopiba” because it is made up of the states of Maranhão, Tocantins, Piauí and Bahia and is the main agricultural frontier of the Cerrado biome This region extends over an area of 12 million hectares, of which 12% is currently destined for grain production (Conab 2016). Over the last three decades, there has been a significant increase in agricultural activities in this Cerrado region, with increasing replacement of native vegetation by cultivated areas, especially for food, fiber and energy production (Santos et al 2016)
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