Agregação como indicadora de qualidade do solo em áreas sob diferentes usos e manejos

Abstract

Inadequate cultural practices in agriculture such as traditional soil preparation promote their degradation, reducing the productivity of the area, and the conventional planting system (CT) is an example of these practices. The no-tillage system (NT) provides maintenance or recovery of soil quality, creating an environment favorable to plant growth. Different techniques and indicators are used in the assessment of soil quality, considering the management used and the type of soil studied. The objective of this study was to evaluate the influence of different vegetation coverings and planting systems on the chemical, physical attributes and on the formation pathways of the aggregates (biogenic and physiogenic). The study was carried out in the municipality of Guaíra, Paraná. For the study, conventional tillage areas (SPC), no-tillage system with 6 years (SPD6) and 18 years (SPD18) of installation, permanent pasture (PP) with 45 years of installation and native forest (MN) were selected. In each area, 4 clods (undisturbed samples) were collected in the 0,00-0.05 and 0.05-0.10 m layers, the samples were air-dried and the aggregates were separated by light pressure between the fingers. The aggregates were screened and classified according to their formation pathway as biogenic or physiogenic, with the characterization of the chemical attributes, stability of the aggregates, granulometric and densimetric fractionation of the aggregates and abundance of 13C being carried out. In the SPC area, lower pH values were observed in the two types of aggregates, whereas in the biogenic aggregates, the lowest (Ca+2) levels were found. In the SPD area, after eighteen years of installation, it was found that for the different formation pathways, there was a greater contribution in the soil organic matter stock, the quantified values being similar to those observed in the MN area, in addition to increases in the stocks of total organic carbon and in labile and recalcitrant fractions of soil organic matter when purchased from SPC. The component analysis evidenced the separation of the evaluated systems in different groups, being observed the distance of the SPC area from the SPD and MN areas.