Resumen

FERNANDEZ, ROMINA et al. Valores umbrales de algunos indicadores de calidad de suelos en molisoles de la región semiárida pampeana. Cienc. suelo [online]. 2016, vol.34, n.2, pp.279-292. ISSN 1850-2067.

The objective of the present study was evaluate the effects of variations in the organic matter contents on soil properties and identify simple y easily determinable indicators that could be useful to monitor soil quality in the semiarid Pampa. The work was carried out in petrocalcic Paleustolls and entic Haplustolls of the Calcic Plain of the semiarid central Pampas. Sites under agricultural use (A) versus native «Caldenal» vegetation (NV) were chosen. In order to characterize soil quality indicators; soil texture (c+l), aggregate size distribution, structural instability (IIE), volumetric aggregate weight (VAW), maximum bulk density (MBD), compaction susceptibility (CS), critical moisture (CM), total organic matter (OM) and its fractions, pH, exchangeable cations, and cation exchange capacity (CEC) were determined. The relationships between OM and its fractions with the physical variables were more significant in soils under A than under NV. A threshold value of approximately 30 g kg^-1 OM was determined above which soils were not susceptible to compaction. Agricultural soils had higher proportions of macroaggregates (> 8mm) and higher VAW than soils under NV. Although MBD, CS, and CM showed good relationships with OM in soils under A and were meaningful indicators of soil physical quality, their use is limited since the Proctor test is not a simple method. Instead, VAW could be proposed as a soil physical quality indicator since its determination is simple, economical, fast, sensitive, and its values were highly correlated with differences in OM.

Palabras clave : Semiarid region; Soil aggregates; Maximum bulk density; Soil organic matter.

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