Resumo

SCHALAMUK, SANTIAGO et al. Pumicitas de Palo Blanco, Catamarca: determinaciones petrográficas y su aracterización como sustrato para plantas. Cienc. suelo [online]. 2016, vol.34, n.2, pp.185-195. ISSN 1850-2067.

There is a need of knowing new inexpensive and suitable inorganic materials for container cropping systems. Some pyroclastic materials such as pumices could fulfill these needs. The general objective of this work was to characterize a pyroclastic material from the sedimentary deposit near Palo Blanco, Catamarca, for its use in substrates. The specific objectives were: 1) Characterize petrographically the pyroclastic particles; 2) Determine the main physical and chemical specific parameters for substrates and 3) Relate the petrographic parameters with the bulk density, porosity and water-air ratio in the original material and three pumice size fractions. Petrographic, mineralogical and chemical analysis and specific parameters determinations for substrates were performed. 2-1 mm fraction presented 79.5% of vitroclasts while 1-0.5 and 0.5-0.25 showed 47.6% and 27.6% respectively, predominating crystal clasts. The coarser fraction had the lowest bulk density (DSs = 618 kgm^-3) and the highest values of total porosity (PT = 0.76 cm³ cm^-3) and air-filled porosity (CA = 0.40 cm 3 cm^-3) (reference values: DSs: 60-250 kgm^-3; PT: 0.85-0.95 cm³ cm^-3 and CA: 0.15-0.30 cm³ cm^-3). In the original material and the fraction 2-1 mm the occluded porosity was 7% and 11% respectively. A correlation was made between the percentage of vitroclasts of the sub-samples and the variables DSs, PT, CA and CRA (water holding capacity) for obtaining the correlation coefficients r = -0.98; 0.98; 0.99 and -0.88 respectively. The internal porosity of vitroclasts has effects on the physical properties of these materials. The air-filled capacity of the 2-1 mm fraction and its low chemical activity could be used in substrate formulations. These materials should be evaluated with plants in future experiments.

Palavras-chave : Pyroclastic material; Porosity; Water release curves; Soilless culture.

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