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Sugarcane productivity is highly variable across space, and knowledge about the spatial distribution of soil physical attributes is important to guide management practices and evaluate the effects of agricultural operations on productivity. Thus, the objective of this study was to determine the best sampling density to represent the physical attributes of an Ultisol Typic Hapludult, to determine the spatial variability of these physical attributes, and to correlate them with sugarcane productivity. A sampling grid was delimited in a sugarcane crop in its first cycle, where 32 samples were collected that were spaced 7 m apart. The samples were collected undisturbed for soil density, total porosity, macroporosity and microporosity determination. In addition, disturbed samples were also collected to determine gravimetric water content. A penetrometer was used to evaluate the soil mechanical resistance. Sugarcane productivity was measured in the same sites. Descriptive statistics and geostatistical analysis were applied to evaluate data variability and correlation between sugarcane productivity and soil physical attributes. The physical attributes of soil: penetration resistance, moisture, total porosity, macroporosity, microporosity, soil density and sugarcane productivity showed spatial dependence, and fit to spherical and exponential mathematical models. Kriging maps identified homogeneous and heterogeneous regions, indicating that the geostatistical techniques were useful for geospatial characterization. The minimum sampling density to estimate sugarcane productivity was 14 samples per hectare and was dependent on penetration resistance and total soil porosity.

The Amazon region has soils of an anthropic formation called Anthropogenic Dark Earths (ADEs). These soils present a higher fertility and are physically different to adjacent local soils. This study aimed to investigate the conditions and spatial behavior of soil physical attributes in ADE areas cultivated with cocoa, coffee, and grassland in southern Amazon. Mapping of three ADE areas was carried out by using sampling grids of 80 m × 56 m with regular spacing of 8 m for the grassland area and 48 m × 88 m with a spacing of 6 m × 8 m for the cocoa and coffee areas. These soils were sampled at the grid crossing points at depths of 0.00–0.05; 0.05–0.10 and 0.10–0.20 m, totaling 88 points in each area. Soil physical analyses of texture, macroporosity, microporosity, total porosity, bulk density, θFC (moisture field capacity), penetration resistance, and aggregate stability were carried out. The data were submitted to descriptive statistics, geostatistics, and multivariate statistics. In the ADE area cultivated with grassland, the attributes showing moderate and weak levels of spatial dependence were those with a greater spatial continuity, i.e. texture, penetration resistance, macroporosity, microporosity, and volumetric moisture. A similar behavior was observed in the ADE areas cultivated with coffee (sand, density, penetration resistance, macroporosity, and microporosity) and cocoa (silt, clay, penetration resistance, macroporosity, and mean weight diameter of aggregates).

The objective of this work is to study the leaf area and biomass production of 4 sugarcane varieties in cane plant cycles, first and second regrowth. The experiment was conducted at Fazenda Jequia in the state of Alagoas, Brazil. A randomized block design with 5 replications was used. The treatments were 4 cultivars: RB92579, SP813250, RB867515 and VAT90212. The length and width of the sheet + 3 were determined as well as the following parameters; the number of tillers per square meter, the number of green leaves, leaf area, and leaf area index in most growing sugarcane in the three crop cycles. The productivity of shoot dry biomass was determined at the time of cane maturity in 3 cycles. Univariate and multivariate analyses were performed. The larger leaf area index of 4.46 m2 m-2 was observed for RB92579 in plant cane cycle. The dry biomass yield was not influenced by varieties having average values of 47, 41 and 31 t ha-1 in the sugarcane plant cycles in the first and second regrowth, respectively. The principal component analysis enabled us to identify from Current Population Survey (CPs) variance which component can contribute to the explanation of the data. Key words: Dry matter accumulation, leaf area index (LAI), principal component analysis.

O conhecimento da distribuição espacial da temperatura, umidade do solo e emissão de CO2 é fundamental para entender o solo como fonte ou dreno de CO2, pois as alterações quanto ao uso e manejo influenciam esta dinâmica. O presente trabalho teve como objetivo investigar, a temperatura, umidade do solo e emissão de CO2 em uma área sob pastagem na região de Humaitá, AM. Demarcou-se uma área de 70 x 70 m, com espaçamento regular de 10 m, totalizando 64 pontos, as medições foram realizadas no período chuvoso e seco. Emissão de CO2 e a temperatura do solo foram registradas utilizando-se de câmara de fluxo portátil e sensor de temperatura do sistema LI-COR (LI-8100). A umidade foi avaliada utilizando sistema portátil TDR, em seguida foram realizadas análises estatísticas descritivas e geoestatísticas. A área de pastagem apresentou maior emissão de CO2 do solo no primeiro período de coleta, caracterizado como período chuvoso. Variações espaciais da emissão de CO2 estão intimamente relacionadas com as variáveis climáticas entre os períodos seco e chuvoso.

The aim of this study was to develop ternary diagrams to estimate water retention in the soil θ-33 kPa and θ-1500 kPa corresponding to the field capacity and wilting point, respectively and available soil water (ASW) using geostatistical approach. The data were extracted from the physical-water base of irrigated areas linked to the Irriga® System belonging to the Rural Engineering Department of the Federal University of Santa Maria. The database provides information regarding the physical characterization of soils in irrigated areas in the states of Rio Grande do Sul, Parana, Goias, Mato Grosso, Sao Paulo, Minas Gerais and Bahia. The data included 11,193 observations covering texture (sand, silt and clay), water retention properties (θ-33 kPa and θ-1500 kPa) and structural properties (bulk density and total porosity). The measured values of the water content in the soil were displayed in the ternary diagram according to the coordinates provided by the particle size distribution determined in the soil samples. Estimates of water content (cm³ cm−³) using the kriging method were performed using only the particle size distribution (sand, silt and clay). To obtain the spatial distribution of soil water retention values in the texture triangle, the use of the ordinary kriging estimator was proposed. The uncertainty analysis resulted in an Root mean square error (RMSE) below 0.048 cm3 cm-3 when comparing the interpolated water content and observed in the values of θ-33 kPa and θ-1500 kPa, with the subdivisions by ranges of bulk density having the lowest uncertainties, highlighting the importance of subdividing the database by classes based on structural properties. Ternary diagrams can act as useful and simplified tools to estimate these properties just by applying the particle size distribution.

Soil erosion generally causes environmental and economic damage to agricultural systems, representing one of the biggest management problems for agriculture. Therefore, understanding the behavior of the erosive process is indispensable for the diagnosis of best conservationist practices of use and management of agricultural resources. The aim of this paper was to characterize the dynamics and spatial aspects of erodibility, its indicators and to evaluate the applicability of the prediction equations of soil loss proposed by Denardin (1990) and Flanagan and Livingston (1995) for cultivated and natural Indian Black Earths (IBEs). Grids with 88 georeferenced sampling points were established for soil sampling at a depth of 0.0–0.20 m. Laboratory analyzes were performed to determine soil particle size and soil organic matter (SOM) analysis. The erodibility factors were calculated and applied univariate analysis, geostatistics and multivariate techniques. Cultivated IBEs exhibit moderate to high soil loss rates even in low slope relief, mainly by runoff. The dynamics of the erodibility factors behave under moderate spatial dependence between the attributes, with high range values and moderate relief influence, indicating high spatial variability, showing the tendency of values of soil losses similar to distances between 15 and 69 m. However, texture and organic matter were the main indicators of erodibility, since medium texture IBEs tend to increase the global and interril erodibility values, and under sandy texture tend to increase erodibility in gully. The increase in SOM elevates erodibility and interril due to the high amount of pyrogenic coal with high capacity to retain water. Therefore, we recommend the adoption of management practices that reduce erosion processes, and mainly avoid the loss of mineralized SOM to maintain crop sustainability.

As terras pretas de índio são caracterizadas por um horizonte A antrópico, de cor escura, com alto teor de matéria orgânica. No cenário atual, muitos aspectos de sua origem e formação ainda não estão elucidados, sendo objetos de pesquisa e discussão perante a comunidade cientifica. O objetivo deste trabalho foi avaliar o perfil da variabilidade espacial da estabilidade de agregados e estoque de carbono em terras pretas de índio sob floresta nativa na região de Novo Aripuanã, Amazonas. Foi delimitada uma área com 4.480 m², estabelecido com dimensão de 56 × 80 m e demarcados pontos equidistantes espaçados a cada 7 e 8 m, totalizando 88 pontos amostrais. Foram coletadas amostras em estrutura preservada em cilindros volumétricos e agregados nas camadas de 0,00-0,05; 0,05-0,10; 0,10-0,20 m, totalizando 264 amostras de solo. Determinou-se os seguintes atributos: diâmetro médio ponderado e o diâmetro médio geométrico, agregados nas classes < 2mm e > 2mm, densidade do solo, carbono orgânico e estoque de carbono. Os dados foram submetidos a análise descritiva e geoestatística. Os atributos estudados apresentaram dependência espacial em todas as camadas. O grau de dependência espacial foi classificado como moderado e forte. Foi constatado o efeito do carbono orgânico nas propriedades da estabilidade de agregados indicando assim a influência direta desta variável. Os semivariogramas escalonados evidenciaram heterogeneidade entre as variáveis avaliadas conjuntamente.Palavras-chave: Amazonas, matéria orgânica, A antrópico. SPATIAL VARIABILITY OF AGGREGATES AND CARBON STOCK IN ANTHROPOGENIC SOILS UNDER NATIVE FORESTS ABSTRACT:The black Indian lands are characterized by an Anthropic horizon of dark color, with high content of organic matter. In the current scenario, many aspects of its origin and formation are not yet elucidated, being objects of research and discussion before the scientific community. The objective of this work was to evaluate the spatial variability profile of the aggregate stability and carbon stock in black Indian lands under native forest in the region of Novo Aripuanã, Amazonas. An area of 4,480 m² was established, established with dimensions of 56 × 80 m and demarcated equidistant points spaced every 7 and 8 m, totaling 88 sample points. Samples were collected in a preserved structure in volumetric cylinders and aggregates in the layers of 0.00-0.05; 0.05-0.10; 0.10-0.20 m, totaling 264 soil samples. The following attributes were determined: weighted mean diameter and geometric mean diameter, aggregates in the classes 2mm, soil density, organic carbon and carbon stock. The data were submitted to descriptive and geostatistical analysis. The attributes studied presented spatial dependence in all layers. The degree of spatial dependence was classified as moderate and strong. It was verified the effect of organic carbon on the stability properties of aggregates, thus indicating the direct influence of this variable. The phased semivariogram showed heterogeneity among the variables evaluated together.Keywords: Amazon; organic matter; A anthropic DOI: http://dx.doi.org/10.5935/2318-7670.v05nespa12

Para se obter uma produção satisfatória é necessário além de um bom manejo, fazer a escolha das cultivares que melhor se adequam a uma determinada região. Nesse sentido, o objetivo deste trabalho foi avaliar cultivares de sorgo sacarino (Sorghum bicolor (L.) Moench) na região de Humaitá, AM. O delineamento experimental foi em blocos ao acaso, compostos por treze cultivares de sorgo sacarino e quatro repetições. Cada parcela foi composta por cinco linhas de 5 m de comprimento, com espaçamentos regulares de 0,70 m nas entre linhas. Foram avaliadas as seguintes variáveis: diâmetro do colmo, altura de plantas, floração, produção de massa verde, ciclo da cultura, altura do colmo e sólidos solúveis totais (°Brix). Os resultados das variáveis estudadas foram submetidos ao teste de Scott-Knott, a 5% de probabilidade. É possível observar diferenças significativas entre cultivares para as características avaliadas. As cultivares de sorgo sacarino BR 501 e Wray tiveram resultados bastante promissores quanto a concentração de sólidos solúveis totais, sendo esta uma das variáveis essenciais na escolha de cultivares para produção de etanol.Palavras-chave: produção, Sorghum bicolor, ciclo, floração. SORGHUM CULTIVARS SACCHARINE ASSESSMENT (Sorghum bicolor (L.) MOENCH) AMAZON REGION, BRAZIL ABSTRACT To obtain a satisfactory output is required in addition to good management, choose cultivars that are best suited to a region. In this sense, the aim of this study was to evaluate sweet sorghum (Sorghum bicolor (L.) Moench) cultivars in Humaitá region, AM. The experimental design was a randomized block, composed of three varieties of sorghum and four replications. Each plot consisted of five lines of with 5m long, with irregular spacing of 0.70 m between the lines. The following variables were evaluated: Flowering, stem diameter, plant height, green mass production, crop cycle, stem height and total soluble solids (°Brix). The results of the variables studied were submitted to the Scott-Knott test at 5% probability. It can observe significant differences between cultivars for the evaluated characteristics. The cultivars of sorghum saccharine BR 501 and Wray had very promising results as the concentration of soluble solids, which is one of the essential variables in choosing varieties for ethanol production.Keywords: production, Sorghum bicolor, cycle, flowering. DOI: http://dx.doi.org/10.5935/2318-7670.v05n06a01

RESUMO: Atualmente compreender os fatores que influenciam as emissões de CO2 em ambientes amazônicos vem sendo discutidos com mais intensidade, devido o acelerado aumento nas variações climáticas (temperatura e precipitação) as quais influenciam nas trocas entre os ecossistemas terrestres e a atmosfera. Diante do exposto, o objetivo deste trabalho foi avaliar a distribuição espacial da emissão de CO2 e atributos do solo sob campo nativo na região de Humaitá, Amazonas. Foi delimitada uma malha amostral de 70 m x 70 m com 64 pontos regularmente espaçados a uma distância de 10 m e georreferenciados. Amostras de solos foram coletadas em cada ponto da malha nas camadas de 0,00-0,05 m e 0,05-0,10 m, para determinação dos atributos físicos do solo e do carbono orgânico, totalizando 128 amostras de solo. Nos pontos de cruzamento da manha foram avaliadas a emissão de CO2, a temperatura e a umidade do solo, utilizando o sistema LI-6400. As emissões de CO2 na área de campo nativo nas condições do presente estudo são fenômenos de natureza complexa, não sendo possível identificar um único atributo do solo ou do ambiente que explique sua variação no espaço, indicando assim que uma dificuldade ao estabelecer relações entre os atributos do solo e emissão de CO2 ocorre devido à complexidade do fenômeno. ABSTRACT: Currently understand the factors that influence the emissions of CO2 in the Amazonian environment has been discussed more intensively, because the rapid increase in climatic variations (temperature and precipitation) which influence the exchanges between terrestrial ecosystems and the atmosphere. Given the above, the objective of this study was to evaluate the spatial distribution of CO2 emissions and soil properties under native pasture in Humaitá region, Amazonas. A sampling grid of 70 m x 70 m with 64 points regularly spaced at a distance of 10 m and georeferenced was delimited. Soil samples were collected at each grid point in layers of 0.00 to 0.05 m and 0.05-0.10 m for determination of soil physical properties and organic carbon, 128 soil samples. At the crossing points in the morning they were evaluated CO2, temperature and soil moisture, using the LI-6400 system. CO2 emissions in native pasture area in the present study conditions are complex nature of phenomena, it is not possible to identify a single soil attribute or the environment to explain the variation in space, thus indicating that a difficulty in establishing relationships between attributes soil and CO2 emission is due to the complexity of the phenomenon.

A conversão de ecossistemas naturais em sistemas agrícolas provoca alterações significativas nos atributos do solo, associado ao crescente desmatamento na região amazônica influenciando a desestabilidade do ecossistema. Dessa forma, objetivou-se com este estudo avaliar a variabilidade espacial dos atributos físicos do solo em área de terra preta de índio (TPI) sob cultivo de café Conilon. Foi demarcado um grid amostral com dimensões de 88 × 64 m, com espaçamento regular de 8 m, perfazendo um total de 88 pontos amostrais. Foram coletadas amostras estruturadas e indeformadas nas camadas de 0,00-0,05; 0,05-0,10; 0,10-0,20 e 0,20-0,30 m. Realizaram-se as seguintes análises físicas: granulometria, estabilidade de agregados, carbono orgânico total (COT), estoque de carbono (EstC), macroporosidade (MaP), microporosidade (MiP), densidade do solo (Ds), porosidade total (PT), resistência do solo à penetração (RP) e umidade volumétrica (θ). Os resultados foram submetidos à análise estatística descritiva e geoestatística. As TPI’s apresentam grande potencial que podem subsidiar o aumento na produção, visto que estes solos apresentam excelente condição que se refere aos atributos físicos, sendo que nas camadas avaliadas estes não apresentaram nenhuma restrição e impedimento ao sistema radicular da cultura.