Revegetation of exposed sub-soil, while a desirable strategy in the recovery processes, often fails due to extreme soil chemical properties, such as low organic matter and pH levels inhospitable to biological activities such as nutrients cycling and plant establishment. This is the case for approximately 800 ha of the Cerrado biome in Brazil, where erecting the embankment of a hydroelectric dam in the 1960’s stripped vegetation, soil, and subsoil layers thereby distorting the soil properties. This work evaluates the effectiveness of restoration management (RM) treatments, to restore the soil quality, including biological activity and chemical attributes. In a factorial scheme, RM treatments include the addition of organic residue from aquatic macrophytes (AM) at 3 rates (0, 16 and 32 t ha^-1), combined with ash from sugar cane bagasse of agroindustrial origin (BA) at 4 rates (0, 15, 30 and 45 t ha^-1). RM samples contrasted samples collected from undisturbed Cerrado (CER) as well as a degraded area without intervention (DAWI). The mechanized RM plots received amendments and reforestation of 10 Cerrado native tree species. After 5 years, vegetation covered up to 60% of the surface in RM treatments receiving AM32 + BA45. AM and BA residues promoted height increases in the introduced plants. All RM treatments promoted lower levels of Al³⁺ than DAWI and CER. The combination of AM32 over the rates of incorporated ash increased soil pH and K values similarly to CER. Microbial-related variables, such as microbial biomass-C was the largest in CER, followed by the RM treatments, and the lowest in DAWI. The microbial quotient was no different between CER and RM treatments. The addition of residues such as AM and BA increased the vegetation covered, improved chemical and microbiological indicators. Thus, the residues used aided the recovery process of intensely degraded soils in the Cerrado area.

Tree residue removal from Eucalyptus plantations after timber harvest can reduce soil functioning by reducing the organic matter input. To assess the effects of residue management systems (RMS) on soil aggregation, carbon (C) and nitrogen (N) content, and biological activities, a field trial was conducted in a commercial Eucalyptus plantation (loamy sand soil) in Mato Grosso do Sul, Brazil. The study assessed three RMS: cut-to-length (CTL), tree-length (TL), and bare litter (BL), respectively. After 21 months, undisturbed soil samples were collected and physically isolated into three aggregate-size fractions: large macroaggregates (LM), medium macroaggregates (SM), and microaggregates (MI). Results showed that these soils are mostly composed of LM (54%), and that removing harvest residues from the growing site included total organic carbon (TOC) by 28%, microbial biomass-C by 20%, fluorescein diacetate hydrolysis by 17%, and β-glucosidase activity by 26%, when compared to CTL. TL outperformed CTL for the proportion of LM and LM-associated TOC. Across fractions, a higher microbial quotient was observed in SM and MI fractions, suggesting that the TOC has higher stability inside the LM. This study suggests that leaving harvest residues on the soil should be recommended for Eucalyptus plantations, especially in low-fertility sandy soils, as it helps in maintaining the soil structure and biological activities critical for soil health and ecosystem function.

Http://dx.doi.org/10.5902/1980509821095Para o sucesso de um processo de revegetação, além de melhorar as condições edáficas da área, deve-se dispor de mudas de boa qualidade, o que pode ser avaliado pelo estado nutricional. Neste trabalho, avaliaram-se os teores foliares de N, P, K, Ca, Mg, S, B, Cu, Fe, Mn e Zn de mudas de Dipteryx alata produzidas a pleno sol ou em cultivo protegido (30% de sombreamento), utilizando como substrato solo degradado, condicionado ou não com resíduo orgânico (32 t ha-1 macrófitas) e com diferentes doses de fósforo (0, 100, 200 e 300 mg dm-3 P2O5), comparativamente às mudas e parte aérea de plantas adultas, coletadas em campo. A cada coleta de folhas em campo, o solo foi coletado e analisado para P, MO, pH, K, Ca, Mg, H+Al, SB e CTC. A mesma análise foi realizada nas unidades experimentais, ao final do experimento. Os resultados mostram que o Dipteryx alata é pouco exigente em P, que os teores foliares, nas mudas de campo, são superiores às plantas adultas em N, P, K e S e inferiores para Ca e que o estádio de desenvolvimento da planta não influenciou os teores foliares de Mg, B, Cu, Fe, Mn e Zn. O resíduo orgânico não foi suficiente para fornecer o N necessário às mudas produzidas. O cultivo a pleno sol propiciou maiores teores foliares de N, P, Ca, Mg, B, Cu, Fe e Mn. Teores foliares de N, P, K, Ca, B, Fe e Zn foram superiores na presença de resíduo orgânico.

The aquatic macrophytes removed from hydroelectric power plants, as well as boiler ash derived from burning sugarcane bagasse can provide nutrients and recover degraded soils more quickly. Thus, this study aimed to evaluate the chemical attributes of a degraded soil in recovery process with mechanical preparation, with or without addition of organic residue (aquatic macrophytes) or agroindustrial residue (ash from sugarcane bagasse), compared to a degraded area without interference in the time of soil removal and in a conserved Cerrado area. The experimental design was a randomized block with four replications. The treatments were: conserved Cerrado soil (T1), area of degraded soil without human intervention since their degradation (T2), soil with mechanized preparation without addition of residue (T3), soil with mechanized preparation and addition of 32 Mg ha-1 of organic residue (T4), soil with mechanical preparation and addition of 45 Mg ha-1 of agroindustrial residue (T5). The orthogonal contrasts analyzed were C1 [(T2+T3+T4+T5)/4 -T1], C2 [(T2+T3) - (T4+T5)], C3 [(T2) -(T3)] and C4 [(T4) - (T5)]. In general, the chemical attributes of degraded soil increased after the incorporation of organic and agroindustrial residue, which is higher than the soil of the conserved Cerrado area. The boiler ash contributed most, to increase the nutrient content and fertility of the degraded soil. Key words: Aquatic macrophytes, ash from sugarcane bagasse, degraded soil, fertility, soil tillage.

1. INTRODUCTION AND OBJECTIVES

A revegetação de áreas degradadas, com comprometimento edáfico e ausência de vegetação, precisa ser precedida por ações que melhorem as características edáficas e assim dar condições ao pleno desenvolvimento das culturas. A espécie Xylopia aromatica, conhecida popularmente como pimenta-de-macaco ocorre no Cerrado e vem sendo utilizada na revegetação de áreas degradadas. Assim, o objetivo com esta pesquisa foi avaliar o crescimento inicial e o estado nutricional de mudas de X. aromatica, introduzidas em área em recuperação, condicionada com macrófitas aquáticas (RO) e cinza do bagaço da cana-de-açúcar (RA), e comparar a mudas da mesma espécie encontradas em Cerrado conservado (CER), para identificação do potencial da espécie na recuperação de áreas degradadas. O estudo foi conduzido em área de supressão da vegetação e dos horizontes superficiais (horizontes A e B) do solo. Na área experimental foram adicionados os resíduos RO e RA em diferentes doses. Mudas de 10 espécies arbóreas de cerrado foram introduzidas na área, entre elas, a X. aromatica. Transcorrido um ano, avaliou-se seu estado nutricional. As mudas na área em recuperação apresentaram teores foliares semelhantes aos das mudas do CER para K, Ca, Mg, B e Mn, e superior para Cu, Fe e Zn. O solo da área experimental apresentou semelhanças ao solo do CER, porém ainda demanda ajustes nos teores de P e matéria orgânica. O crescimento da X. aromatica apresentou melhor resposta no tratamento com 32 t ha-1 de macrófitas e 30 t ha-1 de cinza, doses indicadas para obtenção dos melhores resultados.