ABSTRACT The fertilization management can contribute to a better agronomic performance of rice (Oryza sativa L.) plants in upland conditions. Thus, the objective in this study was to evaluate the development of rice plants fertilized with different doses of nitrogen and phosphorus in upland soil. The experiment was conducted in a greenhouse using pots containing soil collected in the soil top layer of a plinthic alitic Haplic Cambisol. The design was completely randomized with a 4 x 4 factorial scheme, corresponding to 0 (zero), 150, 300 and 450 kg ha-1 of phosphorus and 0 (zero), 100, 200 and 300 kg ha-1 of nitrogen. Plant height, shoot dry matter, grain weight and number of tillers were evaluated. Fertilization with nitrogen and phosphorus positively affects the growth and development of rice plants in Humaitá, Amazonas state, grown in upland soil up to doses between 200 and 300 kg ha-1 of N and around 300 kg ha-1 of P2O5, in a plinthic alitic Haplic Cambisol.

ABSTRACT Amazonian soils have been suffering severe changes resulting from human activities in the region, causing significant changes in soil attributes that can contribute to greater susceptibility to erosion processes. Therefore, the present work aimed to estimate the erodibility in natural and anthropic environments in the southern region of the Amazon. Eight areas in the region were selected, including areas of native forest, savannah, cerradão, pasture and reforestation, delimiting 32 sampling points per area, with collections at a depth of 0.00-0.20 m, totaling 256 samples. Next, texture analysis and quantification of soil organic carbon were performed, and then erodibility was estimated by indirect prediction methods, Tukey’s test, Pearson’s correlation and factorial analysis of principal components. According to the results obtained, it was observed that the evaluated areas of native forest 1 and 2, cerradão and pasture present high susceptibility to erosion in relation to the cerrado, reforestation with genipap, teak and mixed areas. Therefore, it was noted that the high level of erodibility is associated with a greater predominance of sand fraction, K factor, Ki Kr and low clay content, as well as with the management employed in the areas.

RESUMO Nesta pesquisa objetivou-se avaliar os aspectos biológicos e o comportamento alimentar de Aphis gossypii em cultivares de melancia submetidas à aplicação de silício. O experimento foi conduzido no Instituto de Educação, Agricultura e Ambiente da Universidade Federal do Amazonas, Humaitá, Brasil. Utilizaram-se o delineamento experimental inteiramente ao acaso e o esquema fatorial 2×3 (sem silício e com silício; cultivares Crimson Sweet, Fairfax e Charleston), com dez repetições. A aplicação do ácido silícico (1%) foi realizada diretamente no substrato, com dose equivalente a 1 ton SiO2·ha-1, 25 dias após a semeadura. Os pulgões da criação foram mantidos em plantas de pepino, cultivar Caipira. Foram conduzidos ensaios de biologia do inseto para avaliação da duração dos períodos pré-reprodutivo, reprodutivo e pós-reprodutivo, longevidade, número de ninfas e comportamento alimentar por meio da técnica de secreção de honeydew. Realizou-se a análise de variância dos dados utilizando-se o programa estatístico SISVAR e as médias foram comparadas pelo teste de F e Scott–Knott (p ≤ 0,05). A aplicação de silício em plantas de melancia afeta a reprodução e a alimentação de A. gossypii. Plantas de melancia do cultivar Crimson Sweet tratadas com silício apresentam alta resistência à alimentação por A. gossypii.

ABSTRACT This research aimed to evaluate the biological aspects and the feeding behavior of Aphis gossypii in watermelon cultivars submitted to silicon application. The experiment was conducted at the Institute of Education, Agriculture and Environment of the Federal University of Amazonas, Humaitá, Brazil. The experimental design was completely randomized in a 2×3 factorial (with and without silicon; cultivars Crimson Sweet, Fairfax and Charleston), with ten replications. The application of silicic acid (1%) was carried out directly on the substrate using dose equivalent to 1 ton SiO2·ha-1, 25 days after sowing. The rearing of aphids was kept in cucumber plants, cultivar Caipira. Insect biology tests were conducted to evaluate the duration of the prereproductive, reproductive and postreproductive periods, longevity, number of nymphs, and feeding behavior using the honeydew secretion technique. Analysis of variance was performed using the statistical program SISVAR and the means were compared by the F and Scott–Knott test (p ≤ 0.05). The silicon application to watermelon plants affects the reproduction and feeding of A. gossypii. The watermelon plants cultivar Crimson Sweet treated with silicon has high resistance to feeding by A. gossypii.

Resumo Para se avaliar a qualidade do solo e a sustentabilidade em ambientes de Terra Preta Arqueológica da Amazônia, é importante a caracterização dos impactos de uso de solo dos diferentes tipos de cobertura. Sendo assim, o objetivo deste trabalho foi avaliar os atributos físicos e o carbono orgânico em áreas de Terra Preta Arqueológica, no município de Novo Aripuanã, AM, sob os cultivos feijão guandu (Cajanus cajan) e pastagem, em comparação com a cobertura de floresta, com base em técnicas de estatística tradicional univariada e multivariada e de geoestatística. Para isso foram delimitadas malhas com espaçamentos regulares e 88 pontos amostrais georreferenciados por malha. Foram coletadas amostras em blocos de solo com estrutura preservada e anéis volumétricos, para a determinação das propriedades físicas e do carbono orgânico do solo. O feijão guandu e pastagem diferem estatisticamente da floresta, que apresentaram características de estabilidade dos agregados acima da média, mas características texturais e carbono orgânico abaixo da média. O modelo exponencial, pelo semivariograma escalonado, mostrou que atributos físicos do solo apresentaram predominância, com grau de dependência de forte a moderado, sendo a área sob feijão guandu com maior variabilidade dos atributos do solo.

Abstract In order to evaluate soil quality and sustainability in Amazon Archaeological Dark Earth environments, it is important to characterize the impacts of the use of different cover types. The objective of this work was therefore to evaluate the physical attributes and organic carbon content in areas of “Terra Preta Arqueológica”, in the municipality of Novo Aripuanã, AM, under the cultivation of pigeon pea (Cajanus cajan) and pasture, in comparison with forest cover, based on traditional univariate and multivariate statistical techniques and geostatistics. In order to accomplish this, grids with regular spacing and samples with 88 georeferenced points per grid were delimited. Samples of soil blocks with preserved structure and volumetric rings were collected to determine physical properties and organic carbon content. The pigeon pea and pasture soils differ statistically from that of the forest and presented above-average aggregate stability, but texture and organic carbon characteristics were below average. The exponential model showed that the physical attributes of the soil predominated, with a strong to moderate degree of dependence, with the area under pigeon pea presenting the greatest variability of soil attributes.

As Terras Pretas Arqueológicas (TPA) são solos que podem concentrar até seis vezes mais carbono orgânico que solos adjacentes sem horizonte A antrópico, presumindo-se, dessa forma, maior efluxo de CO2 nesses solos. O objetivo deste estudo foi investigar a distribuição espacial do efluxo de CO2, temperatura e umidade do solo em área de Terra Preta Arqueológica sob cultivo de cacau e café no município de Apuí, AM, Brasil. Foram construídas malhas amostrais nas dimensões 42 x 80 m, com espaço entre os pontos de 8 x 10 m e 6 x 10 m para as áreas de cacau e café, respectivamente. Após a etapa de coleta dos dados do efluxo de CO2, temperatura e umidade do solo, procedeu-se a análise estatística descritiva e geoestatística. Os resultados mostraram que os parâmetros avaliados apresentam dependência espacial, com alcance variando de 25 a 40 m para o efluxo de CO2 da área TPA com cacau. O efluxo de CO2 na área de cacau foi superior, com valor médio de 5,49 µmol m-2 s-1, comparado ao 3,99 µmol m-2 s-1 de CO2 da área com café.

The Archaeological Dark Earth (ADE) are soils that can hold up to six times more organic carbon than surrounding soils without anthropic horizons, thus assuming higher CO2 emissions from these soils. The objective of this study was to investigate the spatial distribution of CO2 efflux, temperature and soil moisture in an Archaeological Dark Earth area under cocoa and coffee cultivation in the municipality of Apuí, AM, Brazil. Sample grids of 42 x 80 m were set up, with space between points of 8 x 6 x 10 m and 10 m, respectively, for the cocoa and coffee areas. After data of CO2 efflux, temperature and humidity of the soil were collected, descriptive statistics and geostatistics analyses were done. The results showed that the evaluated parameters exhibited spatial dependence reaching a range of 25 to 40 m for CO2 stream ADE area with cocoa. The CO2 efflux in the cocoa area was higher, with an average value of 5.49 µmol m-2 s-1, compared to 3.99 µmol m-2 s-1 in the area of coffee CO2.

ABSTRACT Soils with an A horizon formed by human activity, an anthropogenic A horizon, are found in the Amazon Region. Few studies have examined the spatial distribution of the properties of these soils. We mapped the spatial variability of some soil properties in an area of Archaeological Dark Earth (ADE) in the Brazilian Amazon. A sampling grid was defined over an area of 42 × 88 m under cacao cultivation in which sampling points were established at a spacing of 6 × 8 m, for a total of 88 points. Samples were collected from the 0.00-0.05, 0.05-0.10, 0.10-0.20, and 0.20-0.30 m depth layers. Soil texture, aggregate stability, and organic carbon (OC) analyses were performed on disturbed soil samples. Undisturbed samples were used to determine soil macroporosity (Macro), microporosity (Micro), total porosity (TP), and soil resistance to penetration (RP). The results were analyzed by descriptive statistic, Pearson correlation (p<0.01), and geostatistics. Soil bulk density, total pore volume, and geometric mean diameter are dependent on the total amount of OC in the ADE area. Increased soil bulk density and RP are proportional to a decrease in OC content and lower Micro and TP. Moreover, soil resistance to penetration is influenced by soil water and clay content with depth.

A escassez de informações sobre o comportamento espacial dos atributos dos solos na região amazônica tem sido preocupação de muitos pesquisadores. Assim, este trabalho teve como objetivos avaliar a variabilidade espacial de atributos químicos do solo e determinar a densidade amostral mínima para caracterizar a variabilidade desses atributos em cinco ambientes amazônicos. Este estudo foi realizado ao sul do Estado do Amazonas, em área com terra preta arqueológica (TPA), floresta, pastagem, agrofloresta e cana-de-açúcar. Nessas áreas, foram estabelecidas malhas de 70 × 70 m, com espaçamento regular de 10 m, totalizando 64 pontos em cada ambiente. Os solos foram coletados na profundidade de 0,0-0,10 m. Foram determinados os atributos químicos (pH em água, MO, P, K, Ca, Mg, H+Al, SB, CTC e V). Os dados foram analisados utilizando-se técnicas de estatística descritiva e geoestatística. Grande parte dos atributos estudados apresentou estrutura de dependência espacial. O modelo esférico foi o que melhor se ajustou aos atributos químicos nos diferentes ambientes, onde somente a cana-de-açúcar evidenciou melhor ajuste ao modelo exponencial. As áreas de TPA e cana-de-açúcar mostraram maior heterogeneidade dos atributos químicos do solo, apresentando menor alcance e maior densidade amostral, e a área com floresta e agrofloresta apresentaram menor variabilidade dos atributos químicos.

The lack of information concerning the variability of soil properties has been a major concern of researchers in the Amazon region. Thus, the aim of this study was to evaluate the spatial variability of soil chemical properties and determine minimal sampling density to characterize the variability of these properties in five environments located in the south of the State of Amazonas, Brazil. The five environments were archaeological dark earth (ADE), forest, pasture land, agroforestry operation, and sugarcane crop. Regular 70 × 70 m mesh grids were set up in these areas, with 64 sample points spaced at 10 m distance. Soil samples were collected at the 0.0-0.1 m depth. The chemical properties of pH in water, OM, P, K, Ca, Mg, H+Al, SB, CEC, and V were determined at these points. Data were analyzed by descriptive and geostatistical analyses. A large part of the data analyzed showed spatial dependence. Chemical properties were best fitted to the spherical model in almost all the environments evaluated, except for the sugarcane field with a better fit to the exponential model. ADE and sugarcane areas had greater heterogeneity of soil chemical properties, showing a greater range and higher sampling density; however, forest and agroforestry areas had less variability of chemical properties.

O avanço de atividades agropecuárias, sem considerar as condições estruturais do solo, finda no detrimento destes ambientes. Este trabalho objetivou avaliar a variabilidade espacial da estabilidade de agregados, densidade do solo, carbono orgânico total (COT) e estoque de carbono de áreas de campo natural e floresta, na região de Humaitá (AM). Os solos foram amostrados nos pontos de cruzamento de uma malha de 70 m x 70 m, em intervalos regulares de 10 m, às profundidades de 0,0-0,05 m; 0,05-0,10 m; e 0,10-0,20 m, totalizando 64 amostras por profundidade. Os resultados da análise geoestatística mostraram dependência espacial dos atributos avaliados. Os menores alcances foram decorrentes das constantes variações na forma do relevo da área de campo natural. Os valores médios respectivos do índice de estabilidade diâmetro médio ponderado (DMP) e COT, em torno de 3,0 mm e 29,0 g kg-1 da camada superficial, similares aos das áreas de campo natural e floresta, confirmam a correlação proporcional entre os teores de COT e o DMP. Todavia, os níveis de densidade do solo superiores a 1,40 kg dm-3 expressam a ineficiência das funções estruturais do solo da área de campo natural. Os valores de estoque de carbono, nas diferentes profundidades, mostraram-se mais favorecidos pelos teores de COT que em razão dos diferentes níveis de adensamento dos solos estudados.

The advancement of agricultural activities without considering the soil structural conditions ceases at the expense of those environments. This study aimed at evaluating the spatial variability of aggregate stability, bulk density, total organic carbon (TOC) and carbon stock in areas of natural grassland and forest, in the region of Humaitá, Amazonas State, Brazil. The soils were sampled at the crossing points of a grid with 70 m x 70 m, at regular intervals of 10 m, at the depths of 0.0-0.05 m, 0.05-0.10 m and 0.10-0.20 m, totaling 64 samples per depth. The results of the geostatistical analysis showed spatial dependence of attributes. The smaller ranges resulted from the constant variations in the relief of the natural grassland area. The mean values for mean weight diameter (MWD) and TOC were respectively around 3.0 mm and 29.0 g kg-1 of the surface layer, similarly to natural grassland and forest areas, confirming the proportional correlation between TOC and MWD. However, the bulk density greater than 1.40 kg dm-3 expresses the inefficiency of soil structural functions in the natural grassland area. The carbon stock contents at the different depths were more favored by TOC than by the different densification levels of the soils evaluated.

As Terras Pretas Arqueológicas (TPAs) são unidades de solo que apresentam como características alta fertilidade, coloração escura e presença de fragmentos cerâmicos. Sobre a formação das TPAs, a hipótese mais bem aceita entre os pesquisadores é que essas foram originadas a partir de processos antrópicos provocados pelos homens pré-colombianos. Diante disso, objetivou-se caracterizar TPAs localizadas nos municípios de Apuí e Manicoré, na região sul do Estado do Amazonas. Foram selecionados sete locais de ocorrência de TPAs, sendo abertas trincheiras e os perfis do solo caracterizados morfologicamente. Procedeu-se à coleta de amostras de solo em cada horizonte para as seguintes análises físicas e químicas: composição granulométrica, argila dispersa em água, grau de floculação, densidade do solo, densidade de partículas e porosidade total, pH em água e KCl, Ca2+, Mg2+, K+ e Al3+ trocáveis, P disponível, H+Al e C orgânico, além dos teores dos óxidos do ataque sulfúrico, óxidos livre e formas mal cristalizadas. A textura dos horizontes A antrópicos variaram de franco-arenosa a franco-argilosa. Os fragmentos cerâmicos e material lítico apresentaram-se em quantidades e profundidades semelhantes no horizonte A dos perfis estudados, sugerindo certa similaridade dos fatores antrópicos que promoveram sua formação. Os horizontes antrópicos dos perfis P3, P4 e P7 apresentaram caráter eutrófico e teores altos a muito altos de fósforo disponível, quando comparados aos perfis P1, P2, P5 e P6, evidenciando heterogeneidade das TPAs.

The Archaeological Dark Earth (ADE) soils are characterized by its high fertility, dark color, and presence of pottery fragments. Regarding the formation of ADE, the most widely accepted hypothesis is that anthropogenic processes involving pre-Columbian populations made them. The purpose of this study is to characterize ADE units located in the Southern Amazon Region, in the cities of Apuí and Manicoré. Seven ADE sites were selected, trenches opened and the soil profiles characterized morphologically. Then, samples of each horizon were collected for analyses of the following physical and chemical properties: particle size, water-dispersible clay, flocculation, soil bulk density, particle density, total porosity, pH in water and KCl solutions, Ca2+, Mg2+, K+, Al3+, available P, H+Al, and organic C. Also, total oxides, free oxides and amorphous forms were analyzed. The texture of the anthropic A horizon ranged from sandy loam to clay loam. The pottery fragments and lithic material were found in similar quantities and at similar depths in the A horizons of the studied soil profiles, suggesting some similarity between the anthropogenic factors of formation. The anthropic horizons of profiles P3, P4, and P7 had a eutrophic character and high to very high levels of available phosphorus, compared to P1, P2, P5, and P6, indicating the heterogeneity of the ADEs.