Cambios inducidos por la implantación de olivos sobre las propiedades edáficas en el sur bonaerense Changes induced by tree olives implantation on soil properties in southern bonaerense

El reemplazo de la estepa graminosa nativa por montes de olivos (Olea europaea L.) en pequeños sectores del sur pampeano afectados al cultivo de trigo ha introducido una modificación drástica en la vegetación como factor pedogenético activo. El impacto de este cambio se evaluó en el horizonte A de los suelos predominantes (Paleustolles Petrocalcicos) bajo montes de olivos (LV2) implantados hace aproximadamente 50 a��os y se lo comparó con el ocasionado por la rotación tradicional trigo (LV3)-vegetación natural (LV1). Se determinó: textura, densidad aparente (Da), pH, carbono orgánico (CO), nitrógeno total (Nt), fósforo disponible (Pd), CIC, bases intercambiables y, además, se estudió la organización micromorfológica. El efecto del cambio de vegetación es notable en las tres situaciones comparadas, no obstante, las variables químicas y la micropedología no reflejan disminución de la calidad del suelo a partir de la introducción de olivos.<br>In small sectors of the southern Pampean region affected by wheat cultivation, the native grassland steppe has been replaced by Olea europaea L. mounts, which introduced a drastic modification of vegetation as an active factor of pedogenesis. The impact of this change was evaluated in the A horizons of the predominant soils (Petrocalcic Paleustolls) under olives mounts of approximately 50 years (LV2) and has been compared to that derived after the traditional rotation wheat (LV3)-native vegetation (LV1). Chemical analyses were performed to analyze the variables commonly used in the evaluation of soil fertility: bulk density (Da), texture, pH, organic carbon (CO), total nitrogen (Nt), available phosphorous (Pd), CIC, exchangeable bases. Moreover, a micromorphological study was done. Increments of 90% magnitude order in CO content, 70% in Nt and >100% in Pd were detected under olive trees cultivation related to a high biomass of olive trees and grass vegetation in the epipedon and to the intense melanization that sustain C/N relationship in acceptable levels. All variables decrease under wheat cultivation (LV3). At microscopic level a higher degree of humic pigmentation, a stronger microstructure (subangular blocky and spongy), darker colors and a higher frequency of excrements were observed under olives compared to grassland and wheat cultivation. The three compared situations denote the notable effect of vegetation change though variables do not reflect a soil quality decrease owed to olive trees introduction. On the contrary, soil physicho-chemical properties proved a substantial improvement contrasting with the detrimental effects in soils affected to wheat cultivation under the current management practices in the studied region.