ABSTRACT:Mining activities generally affect soil quality, degrading it and creating the need for consistent environmental recovery efforts. This study evaluates the influence of monospecific and mixed stands of Sesbania virgata (S) and Eucalyptus camaldulensis (E) on the chemical properties and microbial activity of the soil in a degraded area by clay extraction in the northern part of the state of Rio de Janeiro, Brazil. Four treatments (100S:100 % Sesbania, 100E: 00 % Eucalyptus, 50S:50E: 50 % Sesbania + 50 % Eucalyptus, and DASV: a degraded area with spontaneous vegetation) were established according to a randomized complete block design with three replicates. Samples were collected in the 0.00-0.10 m layer in the rainy season (March) and the dry season (September). The properties evaluated were pH in water; contents of P, K + , Ca 2+ , Mg 2+ , Al 3+ , H+Al, N, and C; C/N ratio; total microbial activity (soil respiration -CO 2 emission); and total enzymatic activity (fluorescein diacetate hydrolysis). The reforestation of degraded areas by clay mining with the species S. virgata and E. camaldulensis either in monospecific or mixed stands increased the nutrient contents, C levels, and total microbial activity in the soil. It was possible to separate the planting systems (100S, 100E, 50S:50E) and the DASV using principal component analysis. In both seasons, soil C contents, chemical properties, and biological variables improved in the planted areas, in contrast with the DASV. The revegetation of degraded areas by mining improved the chemical and biological properties of the soil, leading to higher soil quality in revegetated areas compared to degraded areas with natural vegetation.

RESUMO:O objetivo deste trabalho foi avaliar as inter-relações entre uso do solo, posição na paisagem (posição na topossequência) e seus efeitos sobre atributos físicos, químicos e microbiológicos em solos sob diferentes sistemas de uso da terra em duas topossequências no Noroeste do Estado do Rio de Janeiro. A primeira topossequência consistiu de vegetação espontânea no terço superior e plantio de pupunha nos terços médio e inferior; a segunda topossequência consistiu de pasto nos três terços. Os atributos edáficos determinados foram: densidade do solo, porosidade total e teor de argila; teores de P, Ca, Mg, K, Al e pH; carbono e nitrogênio da biomassa microbiana, respiração acumulada, C orgânico e N total. A análise de agrupamento de Tocher e análise de componentes principais (ACP) foram realizadas para diferentes grupos de variáveis. Inicialmente utilizaram-se os atributos físicos e alguns atributos químicos e depois os atributos microbiológicos, C orgânico e N total. O conjunto dos atributos físicos e químicos foram mais sensíveis que o COS, Nt e atributos microbiológicos em explicar a similaridade e, ou, dissimilaridade decorrentes tanto da posição na topossequência quanto da substituição na cobertura vegetal. Os atributos microbiológicos, COS e Nt evidenciaram a influência da substituição da cobertura vegetal e práticas (e, ou ausência) de manejo na dissimilaridade entre os sistemas de uso da terra. A relevância de atributos físicos, químicos e, ou, microbiológicos na distinção de sistemas de uso da terra vai depender das fontes de variação dos ambientes em que estes sistemas estão sendo estudados.Palavras-chave: análise de agrupamento; análise de componentes principais; método de Tocher; pastagem; pupunha Physical, chemical and microbiological attributes of soils under different land uses in a toposequence in the northwest fluminense ABSTRACT: The objective of this study was to evaluate the interrelationships between land use, landscape position (position in a toposequence) and its effects on physical, chemical and microbiological attributes in soils under different land use systems in two toposequences in Northwest of Rio de Janeiro State. The toposequence 1 consisted of spontaneous vegetation in the summit and pupunha palm plantation in the backslope and footslope; Toposequence 2 consisted of pasture in the three positions. The following variables were determined: bulk density, total porosity and clay content; P, Ca, Mg, K, Al content and pH; microbial biomass carbon and nitrogen, microbial respiration, organic C and total N. Tocher method and principal component analysis (PCA) were performed for different groups of variables. Initially the physical attributes and some chemical attributes and then the microbiological attributes, organic C and total N were used. The groups formed by the Tocher method for the two sets of variables used were confirmed by the PCA. The set of physical and chemical attributes were more sensitive than COS, Nt and microbiological attributes to explain the similarity and, or, dis...

Efeito do triadimenol sobre o desenvolvimento do feijoeiro (Phaseolus vulgaris L.) e atividade microbiológica do solo Effect of triadimenol on the development of bean (Phaseolus vulgaris L.