Resumo

BEHRENDS KRAEMER, Filipe; CASTIGLIONI, Mario Guillermo  e  MORRAS, Héctor José María. Micromorphometric porosity assessment in a typic argiudoll with two intensity uses under no tillage. Cienc. suelo [online]. 2018, vol.36, n.1, pp.138-156. ISSN 1850-2067.

In Argentina and particularly in the Pampa region, no-tillage (NT) is the main cropping system. Within this framework, in recent years two situations have characterized NT: one with low crop sequence intensification and thus high soybean participation, and another with greater crop diversity. In this work two treatments represent these situations, referred herein as poor (MP) and good agricultural practices (BP) respectively, together with a reference situation (AN - natural environment) have been evaluated through micromorphological and micromorphometric methods. The presence of a larger crop proportion during the year and shorter winter fallow periods favored the development of the surface (0-6 cm) macroporosity (> 50 μm) in BP (13%) compared to MP (8.8%) while in the 6-12 cm layer, BP macroporosity decreased to 10% and MP maintained its percentage respect to the topsoil layer. AN presented a surface porosity similar to BP (12%). Porosity differences between treatments were associated with the relative proportion of macropores> 1000 μm which corresponded mainly to the elongated pores. Higher frequency of rounded pores in MP respect to BP and AN was observed; in MP their origin would be related to compaction of microaggregates and individual particles, while rounded pores in BP and AN would be associated with biological channels. In turn, and although macropores with vertical orientation where more frequent in BP respect to MP, elongated pores showed a strong tendency to horizontal orientation in both agricultural managements. Although horizontal planes, associated with platy structures were notorious in both agricultural treatments, some of their features appeared clearly different between treatments at the microscopic level. This paper highlights the value of coupling micromorphological and micromorphometric analyses as a tool to characterize the porosity and structural features in soils under NT, and highlights the morphological heterogeneity of the platy structures found in this cultivation system.

Palavras-chave : elongated pores; platy structure; soybean; pore orientation.

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