Influence of three different land management practices on soil mite (Arachnida: Acari) densities in relation to a natural soil

Intensification of agricultural practices is leading to an increased rate of severe soil degradation in the central area of Argentina, with large areas being converted to arable lands. The application of different management practices to soil impacts edaphic mite populations by altering the organic inputs and by influencing the soil microhabitat. The objective of this paper was to evaluate the influence of three different land management practices on soil mite density in temperate agroecosystems of Córdoba, Argentina, in comparison with a natural soil. Standard abiotic soil properties were also analyzed. Six samples per plot and per sampling date were taken at bimonthly intervals from August 1999 to June 2001. A gradient of increasing soil degradation was evident in physical, chemical and physicochemical soil properties from natural to agricultural plots. Total mite density decreased as soil cultivation increased. However, different responses to land management were observed when comparing the different suborders of mites. Oribatida and Mesostigmata were more sensitive to the agricultural practices than Prostigmata and Astigmata. Densities of the last two suborders seemed to be unaffected by soil cultivation in some periods. Oribatida, Mesostigmata and pooled mite density showed a hump-backed relationship with management intensity, with a maximum in the cattle management. It is concluded that the influence of soil cultivation on soil mites as a whole was negative, with more intensively managed systems tending to reduce mite density, although different suborders were differentially affected by agricultural intensification. We suggest that the reduction of total mite, Oribatida and Mesostigmata densities in the high-input managements is mainly explained by the perturbations produced by conventional agricultural practices and by environmental soil conditions present in the intensively managed sites that were unfavorable for these groups of mites. The implication of the changes reported in mite abundances on soil processes is discussed.