ABSTRACT Adopting land-uses that contribute with a considerable litter input can affect the accumulation, protection, and bioavailability of organic carbon in the edaphic environment, compromising the different compartments of soil organic matter (SOM) and the associated benefits. Moreover, changes in seasons can influence the dynamic of SOM. Notably, the mechanisms involved in SOM stabilization and storage, particularly in agroforestry production areas, are still poorly explored. This study aimed to verify if the contents of soil organic carbon (SOC) and the physical fractions of the SOM are modified as a function of agroforestry systems implemented in the short term, and verify if seasonality can affect the compartmentalization of SOM in agrifood systems. Also, we tested if the carbon management index (CMI) is sensitive to detecting management practices quality across the unmanaged pasture, different agroforestry systems, and a reference area (forest). We measured soil physical properties, SOC content in bulk soil, particular organic carbon (POC), and mineral-associated organic carbon (MAOC) fractions at three different depths (0.00-0.05, 0.05-0.10, and 0.10-0.20 m) in response to the adoption of agroforestry systems. Our results show that after a short period of implementation of agroforestry systems, significant changes were observed in SOC contents and the physical fractions of SOM in the most superficial layers (0.00-0.05 and 0.05-0.10 m), with emphasis on the particulate fraction of SOM. We verified that the seasonality affected the SOC, POC, and MAOC contents. We also found that the CMI index was more sensitive and efficient in detecting changes arising from seasonality and the management practices involved. According to this index, it was possible to verify that the agroforestry system with the highest density of species for biomass production (AS3) has been accumulating more carbon in the soil. Therefore, this study provides relevant information regarding soil carbon management in agroforestry systems.

ABSTRACT: This study evaluated the levels of heavy metals in the soil and castor bean plant after fertilization with sewage sludge (SS) subjected to different stabilization processes. The study was conducted in a Haplic Cambisol with the following treatments: control (CO), fertilization with solarized sewage sludge (SSS), composted sewage sludge (CSS), vermi composted sewage sludge (VSS), limed sewage sludge (LSS), and mineral fertilizer (MF). The experimental design included a subdivided plot scheme with fertilization being the primary factor and soil layers or leaf parts being the secondary factor. The data obtained were analyzed using analysis of variance and the Scott-Knott test with 5% significance. Fertilization with SSS, CSS, and LSS led to the highest increase in Zn in the soil, mainly in the surface layer. In the leaf tissues, Zn and Cu levels were higher with the CO and SSS treatments, whereas the Ni level was higher with SSS, CSS, VSS, and MF treatments. In general, Zn and Cu levels were higher in the leaf limb than in the petiole, whereas Ni, Pb, and Cr levels were higher in the petiole than in the leaf limb. In any case, no symptoms of toxicity in the plants and no risk of soil contamination were observed with any of the fertilization treatments.

RESUMO: O objetivo deste trabalho foi avaliar os teores de metais pesados no solo e na planta de mamoneira em resposta à adubação com lodo de esgoto (LE) submetido a diferentes processos de estabilização. O experimento foi desenvolvido em Cambissolo Háplico com os tratamentos: testemunha, adubação com LE solarizado, LE compostado, LE vermicompostado, LE caleado e adubação mineral. O delineamento experimental foi em esquema de parcelas subdivididas, sendo as adubações o fator primário e as camadas do solo ou as partes da folha o fator secundário. Os dados obtidos foram submetidos à análise de variância e teste de Scott-Knott a 5% de probabilidade. No solo, as adubações com LE solarizado, compostado e caleado promoveram os maiores incrementos dos teores de Zn, principalmente na camada superficial. No tecido foliar, os teores de Zn e Cu foram mais elevados na testemunha e no LE solarizado, enquanto o Ni foi mais elevado nos LE solarizado, compostado, vermicompostado e na adubação mineral. De modo geral, os maiores teores de Zn e Cu ocorreram no limbo foliar em comparação ao pecíolo, enquanto os teores de Ni, Pb e Cr foram mais elevados no pecíolo do que no limbo foliar. Contudo, não foram constatados sintomas de toxidez nas plantas e nenhum risco de contaminação do solo com os diferentes tipos de adubações realizadas.

ABSTRACT Sandy texture soils have a great expression in agricultural areas worldwide. In the Baixada Fluminense, soils with a sandy texture on the surface horizons are striking, and a good part of these areas is destined for producing vegetables using conventional cultivation methods. The sandy texture is one of the great challenges for agriculture due to the low water retention capacity provided to the soil, the rapid decomposition of organic matter, and the intense loss of nutrients by leaching. In these areas, the action of erosive processes is sometimes observed, whether water or wind erosion. The practices carried out in conventional agriculture can accentuate these processes. This study aimed to evaluate the influence of different soil management systems, with different vegetation covers, on the pathways of aggregate formation, the nutrient contents contained therein, and the organic matter fractions, with the objective of using these properties as indicators of soil quality. The study was carried out in an organic production unit, with no-till system (NT) and conventional system (CT), three vegetal covers were evaluated, namely; seed cocktail 1 (C1) (Crotalaria (Crotalaria juncea) (20 kg ha-1), Jack Bean (Canavalia ensiformis) (150 kg ha-1) and millet (Pennisetum glaucum) (60 kg ha-1)), and seed cocktail 2 (C2) (with 50 % of the amount of seeds used in C1), and spontaneous plants (S. P). Undisturbed samples were collected at the layers of 0.00-0.05 and 0.05-0.10 m, and, from these samples, aggregates with a diameter between 9.7 and 8.0 mm were classified according to the formation route (Biogenic or Physicogenic). From these, the chemical properties were quantified (pH, Ca2+, Mg2+, Al3+, P, Na+, K+), and also the carbon fractions (total organic carbon – TOC, mineral-associated organic carbon – MAOC), particulate organic carbon – POC, and free light fraction carbon – LFC). Based on the results, it was verified that the percentage of biogenic aggregates was higher than the physicogenic one in the layer of 0.00-0.05 m, not being verified influences of the vegetal coverage or the management system. Chemical properties did not differ significantly between training pathways. The CT, for the most part, was the system in which the highest values of chemical properties were observed, and in general, the C2 and S.P coatings were the ones that provided the greatest improvements for chemical properties and carbon content.

ABSTRACT This study aimed to evaluate the effect of the application of Siliceous Rocks Powder as a source of K (phonolite and verdete) in natura and calcined at temperatures of 300, 600, 800 and 1000° C, pure and in consortium with dolomitic limestone and coffee husk to corn crop (Zea mays L.). The analyses of the phenological variables, stem diameter, number of shoots, leaves, plants height, weight of dry biomass of the aerial part and the contents of N, P and K, accumulated in the aerial part of the plants were performed. The range of calcination temperature between 300 °C and 600 °C, being the treatments that become K more available to the plants. The treatment that produced the highest biomass was the rocks in mixture (m/m) with coffee husk. The calcination temperatures influenced the biomass production and the content of macronutrients accumulated in the dry biomass of the aerial part. The least efficient treatment in the production of biomass was associated with the rocks in mixture with dolomitic limestone.

ABSTRACT Introduction. Based on research initiated during 1986, which constitutes the baseline information, the resilience capacity of the Red Ferrallitic soils in the southern Karstic plain Havana-Matanzas is demonstrated for the first time, as a result of a multifactorial process, conditioned not only by the intrinsic properties of the soil cover and conditions of use, but also dependent on the geological-geomorphological conditions. Methods. The C1 profile (without apparent erosion), located in an area in biostasis, was used as a baseline to evaluate the magnitude of loss of Red Ferrallitic soils through Karst depressions in different scenarios using the prediction model of Kay et al. (1994). Results. It was concluded that under normal agricultural practices the Red Ferrallitic soils affected by erosion would recover in a period of 50 years, while according to the degree of limestone impurities it would take between 100 to 600 years. It was recommended to the authorities that it was necessary to definitively apply the results obtained for more than three decades in the determination of the specific modalities assumed by the degradation of the Red Ferrallitic soils, so that their degradation ceases to be a myth and becomes a priority issue for the food sovereignty and nutritional education plan of Cuba post-COVID-19, since they represent the maximum potential to satisfy what the country currently demands for agricultural productions.

RESUMEN Introducción. A partir de investigaciones iniciadas durante el año 1986, que constituyen la línea base de la información, se demuestra por primera vez, la capacidad de resiliencia de los suelos Ferralíticos Rojos en la llanura kárstica meridional Habana-Matanzas, como resultado de un proceso multifactorial, condicionado no solo por las propiedades intrínsecas de la cobertura edáfica y condiciones de uso, sino dependiente de las condiciones geólogo-geomorfológicas. Métodos. Se tomó como referencia el perfil C1 (sin erosión aparente), localizado en un área en biostasia como línea base, para evaluar en los diferentes escenarios la magnitud de pérdida de los suelos Ferralíticos Rojos a través de las depresiones kársticas mediante el modelo de predicción de Kay et al. (1994). Resultados. Se concluyó que bajo prácticas agrícolas normales los suelos Ferralíticos Rojos afectados por erosión se recuperarían en un período de 50 años, mientras que de acuerdo con el grado de impurezas de las calizas les tomaría entre 100 años y 600 años. Se recomendó a las autoridades la necesidad de aplicar definitivamente los resultados obtenidos por más de 3 décadas en la determinación de las modalidades específicas que asume la degradación de los suelos Ferralíticos Rojos, para que su degradación deje de ser mito y se convierta en un asunto de prioridad para el plan de soberanía alimentaria y educación nutricional de Cuba post-COVID-19, ya que representan el máximo potencial para satisfacer lo que el país actualmente demanda para las producciones agropecuarias.

ABSTRACT: Reducing soil degradation and its impacts on the environment have been one of the main challenges of the 21st century, exacerbated by a direct link between increases in the human population and soil degradation that raises current and future food security concerns. Despite this, experiences worldwide reveal that degraded land restoration projects have either achieved little success or failed. Thus, understanding the underlying causes and devising appropriate restoration mechanisms is crucial. Soil amelioration using beneficial microorganisms, particularly arbuscular mycorrhizal fungi (AMF), is essential and pragmatic. Glomalin, a type of glycoprotein produced by arbuscular mycorrhizal fungi in the phylum Glomeromycota, contributes to the mitigation of soil degradation. Moreover, AMF and glomalin are highly correlated with other soil physico-chemical parameters and are sensitive to changes in the environment. As a result of this, they have been recommended for monitoring the recovery of degraded soil or stages of soil degradation. In this review, we discuss the role of AMF and glomalin in the restoration of degraded soils, including improvements to the soil structure and soil organic matter (SOM), microbial activity, reduction of fertility loss, bioremediation, and mitigation of the effects of drought and saline stress. We highlight the research gaps and discuss the prospects. This knowledge will improve our understanding of the ecological conduct of glomalin and AMF, stimulate future research, and be useful to sustainable restoration of degraded lands. Furthermore, we discussed the challenges and obstacles in the legislation and future perspectives on the production of inoculants based on AMF in Brazil.

ABSTRACT An update of the karstic morphogenesis in San José de las Lajas polje is carried out, with the objective of making a quantitative evaluation of the of karstic-erosive process advance. It is from a baseline of more than three decades in reference localities, in accordance with the conditions of use and management to which soils have been subjected. It demonstrates the effects of intensive anthropogenesis on the Red Ferrallitic soils, as a result of a multifactorial process, conditioned not only by the intrinsic properties of the soil cover and conditions of use, but also dependent on the geological-geomorphological conditions. The application of the Integrating System of Qualitative and Quantitative Methods allowed characterizing the complex influence of the relief in the evolution of the main morphometric parameters of the dolines with losses between 12.33-15.95 t ha-1 year-1. It converted into length units show reductions in the A+B horizons between 0.98-1.20 mm year-1, which exceed the permissible threshold values in terms of erosion proposed by the USLE and the rates of formation of soils derived from limestone rocks in Cuba. It has a marked tendency to increase, which confirm the need for protection and improvement so that their “immunity” to erosion ceases to be a myth and becomes a priority issue for Food Security in the post Covid-19 development programs in Cuba. These soils represent the maximum potential to satisfy the country's current demand for agricultural and livestock productions.

RESUMEN Se realiza una actualización de la morfogénesis kárstica en el polje de San José de las Lajas, con el objetivo de realizar una evaluación cuantitativa del avance de los procesos kárstico-erosivos, a partir de una línea base de más de tres décadas en localidades de referencia, en conformidad con las condiciones de uso y manejo a que han estado sometidos los suelos, que demuestra los efectos de la antropogénesis intensiva en los suelos Ferralíticos Rojos, como resultado de un proceso multifactorial, condicionado no solo por las propiedades intrínsecas de la cobertura edáfica y condiciones de uso, sino dependiente de las condiciones geólogo-geomorfológicas. La aplicación del Sistema Integrador de Métodos Cualitativos y Cuantitativos, permitió caracterizar la influencia compleja del relieve en la evolución de los principales parámetros morfométricos de las dolinas con pérdidas entre 12,33-15,95 t ha-1 año-1, que convertidas en unidades de longitud muestran reducciones en los horizontes A+B entre 0,98-1,20 mm año-1, que sobrepasan los valores umbrales permisibles en términos de erosión propuestos por la USLE y las tasas de formación de suelos derivados de rocas calizas en Cuba, con marcada tendencia a incrementarse, que confirman la necesidad de protección y mejoramiento para que su “inmunidad” a la erosión, deje de ser un mito y se convierta en un asunto de prioridad para la Seguridad Alimentaria en los programas de desarrollo pos Covid-19 en Cuba, ya que estos suelos representan el máximo potencial para satisfacer lo que el país actualmente demanda para las producciones agropecuarias.

RESUMO: O objetivo deste estudo foi avaliar o efeito da fitomassa de diferentes plantas de cobertura no desenvolvimento da comunidade da fauna epígea em área de cultivo orgânico de berinjela (Solanum melongena, L.). Foi adotado delineamento em blocos ao acaso, com quatro tratamentos de plantas de cobertura: braquiária, crotalária, milheto e coquetel (crotalária, braquiária e milheto), além de uma área de floresta secundária (FR). A fauna epígea avaliada por meio de armadilhas do tipo “pitfall traps” em dois períodos de coletas, aos 110 dias e aos 180 dias, após o corte das plantas de coberturas. Foram coletadas amostras de solo para análise de atributos físicos e químicos. Foram capturados 2032 indivíduos na primeira coleta e 3806 indivíduos na segunda coleta. Os maiores valores de riqueza na primeira coleta foram observados nas áreas milheto e coquetel. A análise de agrupamento mostrou similaridade dos grupos da fauna epígea entre o milheto e braquiária na primeira amostragem e entre o coquetel e crotalária na segunda amostragem. A co-inércia evidenciou covariância significativa entre a fauna epígea da segunda coleta e os atributos do solo. O manejo com plantas de coberturas influenciou de forma benéfica a atividade, riqueza e índices ecológicos, em ambos os períodos de amostragens. A associação positiva entre grupos da fauna e os atributos físicos e químicos mostram a eficiência das plantas de coberturas em cultivo orgânico na promoção de melhorias da qualidade do solo.

ABSTRACT: This study assessed the effect of cover crop biomass on the epigeal fauna of an organic eggplant (Solanum melongena L.) cropping system. A randomized block design was used, with four cover crop treatments: brachiaria, crotalaria, millet, and cocktail (brachiaria, crotalaria and millet). The epigeal faunal indices were determined at each plot. The epigeal fauna of a secondary forest site was also assessed for comparison. Epigeal individuals were collected using pitfall traps at two sampling periods (110 and 180 days after mowing cover crops). Soil samples were collected for determination of physical and chemic properties. 2032 individuals were captured in the first sampling and 3806 individuals in the second. The highest values of wealth in the first collection were observed in the millet and cocktail areas. Cluster analysis showed similarity of epigeal faunal groups between millet and brachiaria plots at the first sampling and between cocktail and crotalaria sites at the second sampling. Co-inertia analysis showed a significant covariance between epigeal fauna at the second sampling and soil properties. The cover crops management had a beneficial influence on the activity, wealth and ecological indexes, in both sampling periods. The positive association observed between epigeal faunal groups and soil physical and chemical properties demonstrates the efficiency of cover crops in improving soil quality in organic cropping systems.

ABSTRACT Currently there is a global debate on the degradation of soils, their magnitude and agro-environmental impact, on which, long-term experimentation provides qualitative and quantitative criteria regarding their capacity for restoration through rational use and management. In this context, research conducted over the past 30 years confirms that the existence of degradation processes in Red Ferralitic soils in Cuba has a multifactorial nature, dependent on geological - geomorphological conditions, extreme weather events and intensive anthropogenesis. Taking into account these aspects, the present work reviews 10 main visions, which have limited the full recognition of the specific modalities assumed by water erosion and erosive - karst in these regions, which reveal the need to adopt a policy so that its protection ceases to be a myth and becomes a National Security issue. Experience shows that the lack of harmonized methods of surveillance and information transfer is one of the causes that generates uncertainty about the state of its degradation.

RESUMEN Actualmente existe un debate global sobre la degradación de los suelos, su magnitud e impacto agroambiental, sobre lo cual, la experimentación a largo plazo aporta criterios cualitativos y cuantitativos respecto a su capacidad de restauración a través del manejo y uso racional. En este contexto, investigaciones realizadas durante los últimos 30 años confirman que la existencia de procesos de degradación en los suelos Ferralíticos Rojos en Cuba tiene una naturaleza multifactorial, dependiente de las condiciones geólogo - geomorfológicas, eventos meteorológicos extremos y la antropogénesis intensiva. Teniendo en consideración estos aspectos, el presente trabajo realiza una revisión de 10 visiones principales, que han limitado el pleno reconocimiento de las modalidades específicas que asume la erosión hídrica y kárstico - erosiva en estas regiones, que revelan la necesidad de adoptar una política para que su protección deje de ser un mito y se convierta en un asunto de Seguridad Nacional. La experiencia muestra que la falta métodos armonizados de vigilancia y transferencia de información, constituye una de las causas que genera incertidumbre sobre el estado de su degradación.

ABSTRACT The research was carried out in the South Plain of the Pinar Río province with the objective of integrally evaluating the geological environments of soil formation and their influence on the processes erosion-sedimentation-contamination by heavy metals (HMs), in localities destined to tobacco crop. To this end, two units with different degrees of intervention were selected: the erosive surface (Consolation of the South unit) and the erosive - cumulative surface (units of Pinar Río, San Juan and Martinez and San Luis). The pedological prospecting work identified four main types of soils. They were at depths of 0-20 cm described and sampled, to characterize the main properties that influence the accumulation of HMs in soils. The analysis carried out indicated that natural conditions do not exert a marked influence on the accumulation and availability of HMs, where the reference values of Cd, Pb, Cu, Zn, Fe, Mn, Ni, Cr and Co are, lower than the standards of quality established for Cuban soils.

RESUMEN La investigación se realizó en la Llanura Sur de la provincia Pinar del Río con el objetivo de evaluar integralmente los ambientes geológicos de formación de los suelos y su influencia en los procesos erosión-sedimentación-contaminación por metales pesados (MPs), en localidades destinadas al cultivo del tabaco. Con tal fin fueron seleccionadas dos unidades con diversos grados de intervención: la superficie erosiva (unidad Consolación del Sur) y la superficie erosivo-acumulativa (unidades de Pinar del Río, San Juan y Martínez y San Luís). El trabajo de prospección pedológica identificó cuatro tipos principales de suelos que fueron descritos y muestreados a la profundidad de 0-20 cm, para caracterizar las principales propiedades que influyen en la acumulación de MPs en los suelos. El análisis realizado indicó que las condiciones naturales no ejercen una influencia marcada en la acumulación y disponibilidad de MPs, donde los valores de referencia de Cd, Pb, Cu, Zn, Fe, Mn, Ni, Cr y Co son inferiores a los estándares de calidad establecidos para los suelos cubanos.

RESUMO O cultivo protegido tem crescido no Brasil. Geralmente, as estufas utilizam plástico transparente e tela de sombreamento na cobertura. A cobertura de plástico, com o passar do tempo, perde a transparência por adquirir resíduos de poluição, poeira e outros detritos. A perda de transparência reduz a luminosidade, a fotossíntese e acarreta a perda de produtividade e de qualidade dos produtos. O objetivo do trabalho foi estudar o impacto do sombreamento sobre a produtividade da cultura da alface e determinar o sombreamento ótimo para alcançar o máximo de produtividade. Foram montadas parcelas dentro e fora da estufa, com quatro sombreamentos com telas pretas (0, 35, 50 e 75%). Os tratamentos foram convertidos em sombreamento real a partir da medição de fluxo de fótons fotossintéticos transmitidos. Os resultados de fitomassa fresca e seca foram tratados e analisados por regressão em função do sombreamento medido. Em condições ambientais de fluxo de fótons fotossintéticos em torno de 1000 µmol m-2 s-1, alcançando até 2000 µmol m-2 s-1 em algumas horas do dia, típico de ambiente tropical, a cultura da alface pode suportar um sombreamento de até 50% sem risco de redução da produtividade. Sombreamentos entre 20 e 35%, nessas condições, são benéficos, podendo garantir o máximo de sua produtividade. Recomenda-se ao produtor de alface em cultivo protegido monitorar a vida útil do plástico, evitando que o sombreamento ultrapasse 50%. Para fins de comparação entre experimentos com sombreamento, propõe-se que seja utilizado o fluxo de fótons incidentes (FFI) para todo o ciclo da cultura, indicando o valor limite mínimo de FFI = 600 mol m-2 ciclo-1 para a alface crespa em temperatura média próxima a 21oC.

ABSTRACT Protected cultivation has grown in Brazil. Generally, greenhouses are covered with transparent plastic film and shading screen. The plastic, over time, loses its transparency due to pollution residues, dust and other debris. The loss of transparency reduces lightness, photosynthesis and leads to losses of productivity and product quality. The losses are not always detectable by the farmer. Additionally, internal shading screens are used to reduce heating transmission to the ground. The objective of this study was to evaluate the impact of shading on lettuce crop productivity and to determine the optimum shading to reach the highest productivity. Plots were set up inside and outside the greenhouse, with four shading levels with black screens (0, 35, 50 and 75%). The treatments were converted to real shading from the photosynthetic photon flux measurement. The results of fresh and dry phytomass were treated and analyzed by regression as a function of the real shading. In ambient conditions of photosynthetic photon fluxes around 1000 μmol m-2 s-1, reaching up to 2000 μmol m-2 s-1 at some hours of the day, typical of tropical environment, lettuce may support a shading of up to 50% without risk of productivity reduction; under these conditions, shading between 20 and 35% is beneficial, and can guarantee its maximum productivity in lettuce cultivation. It is recommended that the lettuce producer in protected cultivation monitors the shelf life of the plastic, avoiding that the shading exceeds 50%. In order to compare shading experiments, one should use the incident photon flux (FFI) for the whole crop cycle, indicating the minimum limit value of FFI = 600 mol m-2 cycle-1 for the crispy lettuce at an average temperature close to 21oC.

Abstract Oil exploration and production generate large quantities of waste, which may contain contaminants such as barium and lead. Therefore, more studies aimed at decreasing the levels of heavy metals in contaminated sites, using methods such as phytoremediation, are needed. In a preliminary assay, samples of soil contaminated with oil drilling waste were incubated with different concentrations (2 or 6 mmol L-1) of ethylenediaminetetraacetic acid (EDTA). Subsequently, an experiment was conducted in a greenhouse to evaluate the phytoremediation potential of the tree Cordia africana. EDTA induced mobilization and translocation of lead, manganese, and iron into the C. africana leaves but had no effect on barium. The quantity of heavy metal contaminants accumulated in the plant vegetative parts showed that C. africana cannot be used as a phytoextractor for the tested metals; however, it can be used as a phytostabilizer.

RESUMO A disposição indiscriminada de resíduos da indústria petrolífera levam a contaminação dos solos e mananciais, afetando toda a biota. O objetivo do trabalho foi avaliar a variabilidade espacial dos teores de bário e chumbo em área de disposição de resíduos de perfuração de poços de petróleo. O Latossolo estudado encontra-se no município de Santa Maria do Oeste, no estado do Paraná-Brasil. Para a determinação da variabilidade espacial dos metais criou-se uma grade de amostragem com 76 pontos. Em cada ponto, foram coletadas amostras de solo nas profundidades: 0-0.3, 0.3-0.6, 0.6-0.9 e 0.9-1.2 m para a determinação dos teores de bário e chumbo. A geração dos mapas de bário e chumbo foi realizada através de interpoladores geoestatísticos com determinação da dependência espacial, modelagem e validação de semivariogramas experimentais e sua interpolação. Selecionou-se 30 amostras com concentrações de bário e chumbo mais elevadas para realização de ensaios de lixiviação e solubilização. Na análise do semivariograma verificou-se dependência espacial, permitindo a confecção de mapas por krigagem para os dois metais. Os elevados teores encontrados foram decorrentes das atividades associadas à perfuração de poços, visto que, não foi encontrado correspondência direta com a geologia das rochas locais e a gênese. As concentrações dos metais foram superiores aos valores de investigação considerando o cenário Agrícola/AP-Máx, caracterizando a área sujeita a "Investigação", pertencendo a Classe 4, área contaminada. Apesar desses metais possuírem baixa solubilidade, demonstrando baixo risco de contaminação de águas subsuperficiais, podem apresentar risco de contaminação de corpos d'água por meio do carreamento desse solo.

ABSTRACT Indiscriminate disposal of waste from the oil industry has led to contamination of soils and water sources and toxic effects in the biota. Thus, this study aimed to assess barium (Ba) and lead (Pb) spatial variability in disposal sites for oil well drilling and prospecting wastes. The soil in the study area is classified as Red Latosol, and the area is located in Santa Maria do Oeste, Paraná State (Brazil). Barium and Pb spatial variabilities were determined using a 76-point sampling grid. The levels of metals were determined in soil samples collected at each sampling point, at the depth ranges of 0.0-0.3, 0.3-0.6, 0.6-0.9 and 0.9-1.2 m. Data were mapped using geostatistical interpolators for spatial dependence determination, modeling and validation of semivariograms, and respective interpolation. Thirty Ba and Pb high concentration samples were selected for leaching and solubilization assays. As semivariogram analysis showed spatial dependence, mapping by ordinary kriging was performed for both metals. The high levels found for both metals arose from well drilling activities, as no direct relationship was found between such levels with geology and genesis of the local rock. The concentrations of the metals were higher than the research values considering the Agricultural / AP-Max scenario, therefore, the study area was characterized as class 4 (contaminated). Although these metals have low solubility, i.e. low contamination risk to subsurface waters, they may pose contamination risks to water bodies by means of soil runoff.

Abstract The objective of this study was to evaluate NBPT, zeolite and humic acid in different concentrations as inhibitors of the activity of the enzyme urease. The activity of the urease enzyme was quantified by the methods proposed by May and Douglas (1976) and Witte and Medina-Escobar (2001). For this reason, two experiments were conducted in a completely randomized design in split plots, in which the incubation periods are the plots and the fertilizers with the inhibitors at the different concentrations are the subplots with three replications. Fifteen fertilizers based on NBPT-coated urea, humic acid and zeolite were used in different concentrations. The two methods of analysis used in the experiment confirmed the efficiency of NBPT in inhibiting the enzymatic action even at low concentration, with 0.02% (m/m) being sufficient to inhibit urease, with no difference between inhibitor concentrations. The addition of humic acid reduced the activity of urease after 36 hours of reaction when the activity of the enzyme was evaluated by the method proposed by May and Douglas (1976). Zeolite did not influence the activity of the urease enzyme when analyzed by the May and Douglas method (1976).

RESUMO Um dos principais fatores limitantes no desempenho das culturas agrícolas e florestais na maioria dos solos tropicais é o efeito tóxico do Al3+. No entanto, algumas espécies vegetais apresentam mecanismos de adaptação que lhes conferem tolerância a essas condições. O objetivo deste estudo foi avaliar o desenvolvimento de três espécies florestais cultivadas em solução nutritiva com diferentes níveis de Al3+. Para tanto, mudas de Acacia mangium, Mimosa artemisiana e Enterolobium contortisiliquum foram cultivadas em solução nutritiva com quatro concentrações de Al3+ (controle, 185, 370 e 555 µmol L-1) durante 95 dias. Ao final do experimento, as plantas foram segmentadas e uma fração conhecida das raízes foi digitalizada para estimativa de área e comprimento radicular. O caule, folhas e o restante das raízes foram secos em estufa de ventilação forçada, sendo determinada a biomassa e os teores de N, P e K no tecido vegetal. As espécies apresentaram padrões de crescimento diferenciados em função do aumento do teor de Al3+ na solução nutritiva, sendo que a Acacia mangium e a Enterolobium contortisiliquum foram mais tolerantes ao Al+3, demonstrando potencial de uso na recuperação de áreas degradadas e com solos ácidos. Os teores de N nas partes das plantas não foram influenciados pelo Al3+, no entanto, a concentração de P aumentou nas raízes das três espécies com níveis intermediários de Al3+, resultando em redução de P na parte aérea da Acacia mangium e Mimosa artemisiana. A concentração de K na Acacia mangium foi reduzida somente no menor nível de Al3+, enquanto para Mimosa artemisiana a redução foi gradativa.

ABSTRACT One of the main limiting factors in the performance of agricultural and forest crops in tropical soils is the toxic effect of Al3+ in soils. However, some plant species present adaptive mechanisms that confer tolerance to these conditions. The aim of this study was to evaluate the development of three tree species grown in nutrient solution with different levels of Al3+. Therefore, seedlings of Acacia mangium, Mimosa artemisiana and Enterolobium contortisiliquum were produced in nutrient solution with four concentrations of Al3+ (control, 185, 370 and 555 μmol L-1) during 95 days of cultivation. At the end of the experiment, the plants were targeted and a fraction of the known roots was scanned to estimate root area and length. The stem, leaves and remaining roots were dried in a forced air oven, being determined the biomass and N, P and K in plant tissue. The species showed different patterns of growth due to the increase of the activity of Al3+ in nutrient solution, and Acacia mangium and Enterolobium contortisiliquum were more tolerant to Al3+, demonstrating potential use in the recovery of degraded areas with acid soils. The N concentration in the plant parts were not influenced by Al3+, however the concentration of P increased in the roots of three species with intermediate levels of Al3+, resulting in reduction of P in shoots of Acacia mangium and Mimosa artemisiana. The concentration of K+ in Acacia mangium was reduced only in the lower Al3+, whereas for Mimosa artemisiana was gradually reduced.