RESUMO Os programas de reflorestamento da Amazônia enfatizam o uso de espécies nativas da região. No entanto, o reflorestamento com espécies nativas requer a produção de mudas de alta qualidade. O presente estudo teve como objetivo avaliar o desenvolvimento e a qualidade de mudas de paricá (Schizolobium parahyba var. amazonicum), espécie nativa da Amazônia com alto potencial para atividades de reflorestamento. Realizamos um experimento em casa de vegetação no qual mudas foram submetidas a tratamentos com presença variável de macro e micronutrientes no substrato, e avaliamos o efeito sobre os atributos funcionais (altura da planta, diâmetro do caule, área foliar específica, matéria seca da parte aérea e raiz) e resposta fisiológica (concentração de clorofila a, b e carotenóides). Nossos resultados mostraram que a omissão de nutrientes afeta significativamente o crescimento do paricá. Considerando as variáveis biométricas e fisiológicas avaliadas, as maiores exigências nutricionais das plântulas foram para N, P, K, micronutrientes, Mg e S, enquanto a qualidade das plântulas foi mantida na ausência de Ca. De modo geral, esta espécie apresenta uso eficiente dos nutrientes disponíveis e potencial de crescimento em solos com baixas concentrações de bases. Portanto, para a produção de mudas de paricá de alta qualidade, devem ser adicionados macro e micronutrientes e o calcário é essencial, mas o bom desempenho das mudas sob omissão de Ca sugere que este elemento não precisa ser adicionado ao solo.

ABSTRACT Amazonian reforestation programs emphasize the use of species native to the region. However, reforestation using native species requires the production of high-quality seedlings. The present study aimed to evaluate the development and quality of seedlings of paricá (Schizolobium parahyba var. amazonicum), a species native to the Amazon with high potential for reforestation activities. We carried out a greenhouse experiment in which seedlings were subjected to treatments with varying presence of major and micronutrients in the substrate, and evaluated the effect on functional attributes (plant height, stem diameter, specific leaf area, shoot and root dry matter) and physiological response (chlorophyll a, b and carotenoid concentrations). Our results showed that nutrient omission significantly affects paricá seedling growth. Considering the assessed biometric and physiological variables, the highest nutritional requirements of seedlings were for N, P, K, micronutrients, Mg and S, while seedling quality was maintained in the absence of Ca. Overall, this species shows efficient use of available nutrients and potential for growth in soils with low concentrations of bases. Therefore, for the production of high-quality paricá seedlings, major and micronutrients should be added and lime is essential, but the good seedling performance under Ca omission suggested that this element does not need to be added to the soil.

ABSTRACT Discovered in 1980 and unleashed an utter gold rush of the modern era, Serra Pelada was the largest open-air mine in Brazil. About 80,000 gold prospectors worked there until 1984, when the gold pits were flooded. The environmental impact caused by mining inflicted irreversible damage to the ecosystem, with the formation of a large lake and piles of waste rock and sterile overburden, still evident 28 years after the mine was closed. This study aimed to evaluate the available and pseudo total contents of potentially toxic elements (PTEs), the contamination and pollution levels, and to understand how the biological soil factors are related to the chemical properties of the soil and the available PTE contents in the Serra Pelada - Amazônia, Brazil. Soil was collected from seven areas around the lake: Area 1 - margin of the mine without waste and/or sterile deposits; Area 2 - margin with waste and/or sterile deposits; Area 3 - area with sterile deposit; Area 4 - mine tailings, denominated curimã by the prospectors, from which gold had been extracted; Area 5 - sediment dredged from the lake in the mine pit; Area 6 - area with agroforestry system; Area 7 - riparian forest, unaffected by the artisanal gold extraction process (control treatment). Apart from selenium (Se), all evaluated elements, in at least one of the studied areas, exceeded the contents of the investigation values (defined as the content of a given substance in soil or groundwater above which the human health is under potential direct or indirect risks, considering a standardized exposure scenario) in agricultural areas in Brazil, as determined by the National Council of the Environment. Soil enrichment and contamination with Co, Ba, Mn, and Hg were investigated. Principal component analysis showed that the available levels of PTEs influenced the soil biological properties, in particular basal respiration, indicating that important ecosystem processes are being affected by PTE contamination.

A exploração mineral é uma das principais fontes de contaminação dos solos por elementos potencialmente tóxicos (EPTs). O objetivo foi avaliar os teores totais e disponíveis de boro (B) estrôncio (Sr) e vanádio (V) em solos de Serra Pelada e inferir sobre a contaminação por estes elementos. Os teores totais e disponíveis foram extraídos com água régia e ácido clorídrico, respectivamente. A determinação foi feita por espectrometria de emissão ótica com plasma acoplado indutivamente. Foram calculados o fator de contaminação (FC), fator de enriquecimento (FE) e o índice de carga poluente (ICP). Os teores totais e disponíveis encontrados são altos, o que foi atribuído principalmente ao material de origem. O V foi o elemento com maior FE (7,8), o que mostra que a ação antrópica a partir das atividades de garimpagem causou o enriquecimento das áreas com este elemento. O FC também foi maior para V, chegando a 3,40 no sedimento retirado da mina. O elevado FE indica que houve enriquecimento por EPTs nos solos de Serra Pelada devido as atividades antropogênicas. A partir dos valores do FC e do ICP infere-se que houve contaminação dessas áreas, o que pode representar risco ao ecossistema circundante e a população que habita a região.

Mineral exploration is one of the main sources of soil contamination by potentially toxic elements. The objective was to evaluate the total and available levels of boron (B), strontium (Sr), and vanadium (V) in soils of Serra Pelada and infer if these soils were contaminated by these elements. The total contents were extracted with h aqua regia in digester block, the content availability were extracted with 0.5 mol L-1 hydrochloric acid, the determination was made by optical emission spectrometry with inductively coupled plasma (ICP OES). The contamination factor (FC), enrichment factor (EF) and the pollutant load index (PLI) were calculated. OV was the element with the highest EF 7.8, which showed that human action from the mining activities caused the enrichment with this element in the area. The FC was also higher for V, reaching 3.40 in sediment removed from the mine. On average the index pollution load (PLI) showed that there was contamination in the area by metals. The FC and the PLI showed that there was contamination of these areas by the studied elements, which may represent a risk to the surrounding ecosystem and the population inhabiting the region.

AbstractSoil biological properties have a high potential for use in assessing the impacts of crop systems. The objective of this study is to evaluate the effects of cropping systems on the biological attributes of an oxisol in the Amazonian state of Pará. The treatments consisted of approximately 20-year-old secondary vegetation, recovered pasture, no-tillage systems (NT) maintained for 4 and 8 years after planting with corn (Zea mays L.) and soybean (Glycine max L.), and conventional tillage (CT) systems every 2 years after planting with rice (Oryza sativa L.) and soybean. The microbial biomass to nitrogen ratio was higher in the NT system (0.68 mg kg–1), and the NT system had greater microbial NT8. Thus, the contributions of organic matter from straw improved the soil quality in these areas. The total organic carbon (TOC) content was greater in the secondary forest and CT areas (46.7 and 48.0 mg kg–1, respectively), potentially due to the higher amounts of organic matter and organic matter mineralization in these areas. However, the largest TOC stocks were observed in the pasture, which corresponded with greater carbon storage (63.5 Mg ha–1). By contrast, the no-till systems were not efficient for storing C, with concentrations of 5.0 and 5.3 Mg ha–1 in NT-4 and NT-8, respectively. These results may reflect the short period that these systems were adopted and the vast microbial activity that was observed in these areas, with microbial quotients of 8.03 and 10.41% in NT-4 and NT-8, respectively.

Estudos que visem à seleção de espécies, ou de grupos de espécies de plantas de cobertura do solo adaptadas as condições edafoclimáticas amazônicas parece ser uma estratégia viável para a melhoria da qualidade ambiental por propiciar o estabelecimento do SPD atenuando problemas relacionados ao monocultivo. O objetivo foi avaliar o comportamento de plantas de cobertura, no Nordeste paraense, quanto a persistência, tempo de meia vida, teor e acúmulo de macronutrientes e relação C/N na palhada, em Argissolo Vermelho Amarelo. O delineamento experimental foi em blocos ao acaso, com cinco tratamentos e cinco repetições. As plantas foram cultivadas a partir do mês de julho e cortadas aos 105 dias de cultivo e então foi feita a avaliação da produção. Ao final dos 84 dias a percentagem de cobertura do solo correspondeu a 97, 85, 52, 50 e 15%, para a braquiária (Brachiaria brizantha) (syn. Urochloa), capim colônia (Panicum purpurascens), feijão de porco (Canavalia ensiformes), milheto (Pennisetum americanum) e crotalária (Crotalaria juncea,), respectivamente. A braquiária apresentou maior produção de matéria seca (9.696 kg ha-1), elevada relação C/N (38,4), alto tempo de meia vida (86,5 dias) e grande persistência no campo. O feijão de porco apresentou alta produção de matéria seca (8.950 kg ha-1), porém menor relação C/N (17,4) e tempo de meia vida (39 dias), quando comparada as gramíneas. Por estas características, a braquiária e o feijão de porco são espécies com potencial utilização como plantas de cobertura no SPD no estado do Pará.

Studies to select one or more species of coverage plants adapted to Amazonian soil and climate conditions of the Amazon are a promising strategy for the improvement of environmental quality, establishing no-till agricultural systems, and thereby reducing the impacts of monoculture farming. The aim of this study was to assess the persistence time, half-life time, macronutrient content and accumulation, and C:N ratio of straw coverage in a Ultisol in northeastern Pará. Experimental design was randomized blocks with five treatments and five replicates. Plants were harvested after 105 days, growth and biomass production was quantified. After 84 days, soil coverage was 97, 85, 52, 50, and 15% for signalgrass (Brachiaria brizantha) (syn. Urochloa), dense crowngrass (Panicum purpurascens), jack bean (Canavalia ensiformes), pearl millet (Pennisetum americanum) and sunn hemp (Crotalaria juncea,), respectively. Signalgrass yielded the greatest dry matter production (9,696 kg ha-1). It also had high C:N ratio (38.4), long half-life (86.5 days) and a high persistence in the field. Jack bean also showed high dry matter production (8,950 kg ha-1), but it had low C:N ratio (17.4) and lower half-life time (39 days) than the grasses. These attributes indicate that signalgrass and jack bean have a high potential for use as cover plants in no-till agricultural systems in the State of Pará.