Bioindicadores de qualidade do solo no monitoramento do manejo da cobertura do solo e relação com a erosão hídrica na cultura da Oliveira (Olea europaea L.)

Abstract

The olive tree (Olea europaea L.) is a crop brought from the Mediterranean region that in the last decades was introduced in Brazil and its main product is olive oil. The crop brought with it several challenges related to its cultivation and management, and these directly impact the soil microbiota. The objective of this study was to evaluate the effect of soil collection position in the plot, soil aggregate size, and olive cover crop management on soil chemical and biological indicators in the tropical region of southeastern Brazil. The experiment was conducted in entirely randomized blocks, arranged in a 2x3x5 factorial scheme, with three repetitions. The factors considered were: two positions in the standard plot (subplots in the upper and lower third), three soil aggregate sizes (8-4 mm, 4-2 mm and 2-0 mm) and five cover crop management [olive grown in bare soil (OD); olive trees under cover (OD); olive trees under cover (OVR); olive trees under cover (OVRC); olive trees under cover (OVH); and bare ground (SD)). The experimental procedure consisted of collecting one composite sample per subplot at a depth of 0-5 cm. The biological indicators evaluated were microbial biomass carbon (MBM), soil basal respiration (SBR), metabolic quotients (qCO2), easily extractable glomalin-related soil protein (GFE), and β-glucosidase (β-Glu) activities. The chemical indicators evaluated were soil fertility parameters and soil organic matter (MO). Data were submitted to analysis of variance and test of means, in addition to principal component analysis. The results related to the chemical indicators only pH showed significant difference under the effect of the subplot position and H+Al showed significant difference under the effect of the interaction of factors. On the other hand, when related to soil cover management, pH, K, Ca, Mg, t, SB (base sum) and MOS presented higher values in OVR and OVRC. H+Al showed similar values in OD, OVH, and SD management. As for bioindicators, high values were found in RBS and qCO2 in the lower thirds of the subplots. Higher values of β-Glu and GFE in the aggregate size <2 mm. High values of CBM, RBS were found in OVR and similar values of qCO2, β-Glu and GFE were found in OVR and OVRC when related to land cover management. Principal component analysis showed high variation, however, most of the chemical and biological indicators were more expressive in OVR and OVRC. The management of cover as in OVR and OVRC provided greater accumulation of organic matter and consequently favor the main microbial processes, thus contributing to better soil health.