ABSTRACT Mining is a significant driver of soil mobilization, which impacts its physical, chemical, and biological properties. Changes in land-use affect the distribution of organic matter fractions in stable aggregates, a process that is still poorly understood, especially in drastically altered areas. Recovering and monitoring soil quality to ensure the sustainable development of agricultural crops in these areas after mining is challenging. This study aimed to evaluate the influence of agronomic practices in soil rehabilitation in a bauxite-mined area after three years of field experiment installations through an assessment of organic properties in soil and aggregate classes; an attempt was also made at proposing and elaborating a Soil Quality Index (SQI), which encompasses the soil’s physical, chemical, and organic properties. Different combinations of fertilization treatments and ground cover plants intercropping with coffee were evaluated as rehabilitation practices. The results showed that after three years of rehabilitation, when organic (OF), chemical (CF), and OF+CF fertilizers were applied to the areas of coffee intercropped with Brachiaria (B), they provided higher C and N contents to the soil and aggregates classes, as well as the compartments of soil organic matter (SOM). The minimum set of soil quality indicators for reclaimed bauxite-mined areas was composed of organic indicators: labile organic carbon (LOC) and mineral-associated organic matter (C-MOM); chemical indicators including pH and effective cation-exchange capacity (t), and physical indicators such as the bulk density (BD) and stable aggregates index in water (SAIW). The t and pH were the variables most sensitive to the management systems implanted during the rehabilitation of the mined area, and, therefore, were considered the best indicators of soil quality. Brachiaria was the cover plant that contributed most to improving the soil quality of mined bauxite areas by increasing the SQI, especially when fertilized. In general, when applied to the Brachiaria, the OF+CF fertilization presented a SQI of 0.78, differing statistically from that of the natural vegetation (1.00). Fertilizers and cover crops in association with coffee in the bauxite-mined areas improved the physical, chemical, and organic properties of the soil, thus representing a viable option for reconditioning mineral exploration areas.

O potencial produtivo da cana-de-açúcar decorre de fatores relacionados ao clima, ao solo e à variedade cultivada. Sistemas de manejo que proporcionem a adição de resíduos orgânicos ao solo podem provocar alterações em seus atributos físicos, favorecendo o crescimento do sistema radicular e a produtividade da canade-açúcar. O objetivo deste trabalho foi avaliar os efeitos de diferentes sistemas de manejo com cana-de-açúcar com diversos níveis de adição de resíduos orgânicos sobre a distribuição e os índices de estabilidade de agregados de um Latossolo Amarelo distrocoeso dos tabuleiros costeiros de Alagoas. Foram selecionadas áreas em talhões de produção com a cultura da cana-de-açúcar: uma área cultivada sob sistema de manejo irrigado (SMI), uma área sob sistema de manejo de fertirrigação com vinhaça (SMV) e uma área sob sistema de manejo com aplicação de vinhaça + torta de filtro (SMVT). Esses sistemas de manejo foram comparados entre si e em relação a uma testemunha-padrão, representada por um fragmento de Mata Atlântica (MN). Para avaliar a distribuição e os índices de estabilidade de agregados, amostras do solo foram coletadas ao acaso, nas áreas submetidas aos diferentes sistemas de manejo, nas profundidades de 0-0,20, 0,20-0,40 e 0,40-0,60 m, sendo retiradas num ponto situado nas entrelinhas da cana-de-açúcar. Os resultados foram submetidos à análise de variância e as médias comparadas pelo teste de Tukey a 5 %. Estudos de correlações simples foram realizados entre algumas variáveis medidas. Os resultados permitiram concluir que os diferentes sistemas de manejo promoveram alterações na distribuição de agregados do solo e a estabilização dos agregados na camada superficial dependeu do teor de matéria orgânica e da ação dos ciclos sucessivos de umedecimento e secagem do solo. Os estudos de correlações entre o carbono orgânico total e os índices de estabilidade dos agregados apresentaram correlações significativas e positivas.

The potential yield of sugarcane depends on factors related to climate, soil and the plant variety. Management systems that provide the addition of organic waste to the soil can cause changes in physical attributes of the soil, enhancing the growth of the root system and sugarcane yield. The objective of this study was to evaluate the effects of different management systems at several levels of organic residue addition on the distribution and indices of aggregate stability of dystrophic cohesive Yellow Latosol of coastal plains, in the State of Alagoas. Plots were selected in the following sugarcane-growing areas: area under irrigation management system, area fertigated with vinasse, and an area under application of vinasse + filter cake. These management systems were compared to each other and to a control (native forest). To evaluate the distribution and stability indices of soil aggregates, soil samples were randomly collected in the different areas, at the depths 0-0.20; 0.20-0.40 and 0.40-0.60 m, at points between two neighboring sugarcane rows. The results were subjected to analysis of variance and the mean compared by the Tukey test at 5 % significance. Simple correlation analysis was performed between some measured variables. Results showed that the different management systems induced changes in the aggregate distribution and that the stabilization of soil aggregates in the surface layer dependeds on the organic matter content and the action of successive cycles of soil wetting and drying. The studies of simple correlations showed that total organic C and aggregate stability indices were significantly and positively correlated.