SOIL FERTILITY AND HUMIC SUBSTANCES IN AN AREA OF CLAY EXTRACTION REVEGETATED WITH EUCALYPT AND LEGUMES IN THE NORTH OF RIO DE JANEIRO STATE

A revegeta\ue7\ue3o de \ue1reas de extra\ue7\ue3o de argila com eucalipto e leguminosas pode favorecer a melhoria dos atributos qu\uedmicos do solo. O objetivo do trabalho foi avaliar a influ\ueancia de plantios puros e consorciados de leguminosas e eucalipto na fertilidade do solo e nos teores de carbono org\ue2nico total e das subst\ue2ncias h\ufamicas, em uma cava de extra\ue7\ue3o de argila no Norte Fluminense. O solo original da \ue1rea da cava em estudo \ue9 um Cambissolo H\ue1plico S\uf3dico gleico, no qual a camada superficial (espessura de 20 cm, aproximadamente), com maiores teores de mat\ue9ria org\ue2nica, foi retirada e devolvida ao fundo da cava ap\uf3s a extra\ue7\ue3o da argila. A cava foi nivelada mecanicamente e mantida sob pousio durante dois anos. A revegeta\ue7\ue3o foi realizada com as esp\ue9cies Genus camaldulensis (Euc), Acacia mangium (Ac) e Sesbania virgata (Sesb), em plantios puros e consorciados. O delineamento experimental utilizado foi o de blocos casualizados com sete tratamentos (plantios puros de Euc, Ac e Sesb; plantios consorciados de Euc + Ac, Euc + Sesb, Ac + Sesb; e \ue1rea degradada com vegeta\ue7\ue3o espont\ue2nea (ADVE)) e tr\ueas repeti\ue7\uf5es. Aos 48 meses ap\uf3s implanta\ue7\ue3o dos sistemas foram coletadas amostras de solo na camada de 0,00 a 0,05 m, em que se avaliaram algumas vari\ue1veis da fertilidade do solo (pH em \ue1gua, P, K+; Ca+2, Mg+2, Na+, Al+3, H+Al), carbono org\ue2nico total (COT), nitrog\ueanio (N) e quantificado o carbono das subst\ue2ncias h\ufamicas em carbono da humina (C-HUM), carbono da fra\ue7\ue3o \ue1cido h\ufamico (C-FAH) e \ue1cido f\ufalvico (C-FAF). Observou-se que todos os plantios promoveram aumentos nos teores Ca, Mg, P, K, N, COT, C-HUM, C-FAH e C-FAF em rela\ue7\ue3o \ue0 ADVE. A revegeta\ue7\ue3o de \ue1reas de cava de extra\ue7\ue3o de argila no Norte Fluminense com plantios puros ou consorciados de eucalipto e leguminosas, acarreta em melhorias da fertilidade do solo e dos teores de carbono e nitrog\ueanio totais do solo e do carbono das subst\ue2ncias h\ufamicas. Aos quatro anos ap\uf3s a revegeta\ue7\ue3o, os sistemas mais indicados, de uma forma geral, para acarretar em aumentos dos teores de COT, N total, Mg, soma de bases e capacidade de troca cati\uf4nica, destaca-se o plantio de ac\ue1cia, dentre os plantios puros, e o plantio de eucalipto + sesb\ue2nia, dentre os plantios consorciados.Al\ue9m disso, o cons\uf3rcio eucalipto + sesb\ue2nia, apresentou um dos maiores teores C da fra\ue7\ue3o humina.The revegetation of areas of clay extraction with eucalypt and legumes can promote the improvement of soil chemical atributtes. The aim of this study was to evaluate the influence of pure plantations and intercropping of legumes and eucalypt on soil fertility and the content of total organic carbon and humic substances, in a mining digging clay in North Fluminense. The original soil dig area under study is a Inceptsol where the surface layer (thickness of 20 cm approximately), with higher concentrations of organic matter was removed and returned to the bottom of the dig after the extraction of clay. The dig was leveled mechanically and kept under fallow for two years. Revegetation was performed with the species Eucalyptus camaldulensis (Euc), Acacia mangium (Ac) and Sesbania virgata (Sesb), in pure and intercropped. The experimental design was a randomized block design with seven treatments (pure stands of Euc, Ac and Sesb; Intercropping of Euc + Ac + Euc Sesb, Ac + Sesb, and degraded area with natural vegetation (DANV)) and three replications. At 48 months after implantation of the systems were sampled soil layer from 0.00 to 0.05 m, which evaluated some variables of soil fertility (pH, P, K+, Ca+2, Mg+2, Na+, Al+3, H + Al), total organic carbon (TOC), nitrogen (N) and quantified the carbon of humic substances in the humin carbon (C-HUM), humic acid carbon (C-FAH ) and fulvic acid (C-FAF). It was observed that all stands promoted increases in the concentration Ca, Mg, P, K, N, TOC, HUM C-C-C-FAF and HAF relative to DANV. The revegetation of areas of mining digging clay in North Fluminense pure stands or mixed with eucalypt and legumes, leads to improvements in soil fertility and carbon and total soil nitrogen and carbon of humic substances. At four years after revegetation systems are indicated, in general, to result in increases in TOC, total N, Mg, sum of bases and cation exchange capacity, there is the planting of acacia plantations among pure, and the planting of eucalypt + sesbania, among Intercropping. In addition, the consortium eucalypt + sesbania, presented one of the highest levels of C humin fraction