Uso da terra e a qualidade microbiana de agregados de um Latossolo Vermelho-Amarelo

Abstract

Most studies related to soil aggregation associate the effect of managements or land use types with the organic matter content. However, a direct evaluation of microorganisms and their processes in undisturbed soil allows a better understanding of the real effect of different managements. The objective of this study was to evaluate the changes induced by different types of land use (pasture, eucalyptus forest, araucaria forest, conventional tillage with carrot, and conventional tillage with pumpkin) on soil chemical properties (pH, Ca, Mg, Al, P, K, S, and organic matter), physical properties (mean geometric diameter, mean weight diameter, bulk density, and particle density), and on the microbial quality (microbial activity and carbon, total extraradical mycelium of arbuscular mycorrhizal fungi, and metabolic quotient - qCO2) of the aggregate size classes (I- 4.00 to 2.36 mm, II - 2.36 to 1.18 mm, III - 1.18 to 0.60 mm; IV - 0.60 to 0.30 mm, V - 0.30-0.15 mm) of a Red-Yellow Latosol in the South of Minas Gerais. The results showed that the land use affected the formation, size and microbial quality of aggregates. In the smaller aggregates (classes IV and V) extraradical mycelium of fungi and microbial biomass were reduced, and metabolic activity and quotient increased, regardless of the land use. The microbiological quality of larger aggregates (between 0.60 to 4.00 mm or I, II and III), in soil under araucaria forest was similar to all size classes of soil aggregates under eucalyptus forest, while the quality of smaller aggregates (< 0.60 mm or IV and V) was similar to all aggregate size classes under pasture. Under conventional cultivation, conversely to the other types of land use, the aggregates had a low microbial quality and relationship with soil fertility.