Organic matter fractionation in aggregates typical Argiudolls southeastern Buenos Aires and its relation to different soil uses. A preliminary study

ALVAREZ, M.F., OSTERRIETH, M. AND J.L. DEL RÍO.

Environmental Earth Sciences

Springer-Verlag

Año: 2011 p. 1 - 11

1866-6280

Organic matter is a fundamental factor in the biogeochemical cycle of carbon; it influences the chemical, physical, and biological properties of the soil. The aim of this paper is to determine the organic fractions in the three predominant morphologies of aggregates found in Typical Argiudolls of the Buenos Aires southeastern area and to link them to different soil uses, as possible indicators of soil quality. The study was carried out in the basin de Los Padres Pound (General Pueyrredon, Buenos Aires). We analyzed the first 5 cm of mollic epipedons of plots with different soil uses: (a) cultivated plots, (b) pine and eucalyptus forests, (c) pastures, and (d) a natural plot in the de Los Padres Pound Reserve as a reference. The percentage of soil organic carbon (SOC), light organic carbon (LOC), fulvic acids (FA), humic acids (HA), and humins (H) in elongated, quadrangular and spherical aggregates were determined. The results show slight variations in SOC (7.2–8.6%) in the spherical aggregates of all the plots and a greater variability in elongated and quadrangular aggregates (5.6–10% and 6.9–13.6%, respectively). HA are minimal in the agroecosystems with extreme values of 0.02% in the spherical aggregates of cultivated plots, and maximal in the elongated and quadrangular aggregates of natural plots (0.3–0.5%). Fulvic acids display a similar behavior, while H decrease slightly with the morphologies and the different practices. The substantial decrease of humic substances in cultivated plots translates into a lower biologic activity; this, in turn, influences the aggregation, thus lowering the structural stability of these plots, which have been under agro-horticultural management for more than 50 years.