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O objetivo do estudo foi propor um arranjo metodologico com auxilio do modelo USLE, de modo a sugerir o melhor uso do espaco em funcao de variaveis erosivas, utilizando a bacia hidrografica como unidade de planejamento. Os parâmetros do modelo USLE foram espacializados usando o software ArcGis 10.5, para o estudo de caso da Bacia da Cachoeira Cinco Veados-RS, e os valores erosivos foram categorizados de acordo com a metodologia de Ribeiro 2006. A partir disso, a ideia foi reclassificar as areas em aptas e nao aptas ao uso testado conforme dois criterios limites adotados como maximo aceitavel de perdas (20 e 50 t.ha -1 .ano -1 ). A proposta metodologica consiste na construcao de duas estrategias de analise: a primeira e a construcao de um mapa tematico, considerando uma ordem prioritaria de usos na bacia, onde o uso mais perdulario foi analisado primeiro (Roteiro de Analise Hierarquica Entre Usos); a segunda, consiste na construcao de mapas que correspondem a cenarios com areas da bacia aptas a um determinado uso, segundo o criterio de classificacao utilizado, e o seu cruzamento com o mapa de uso atual (Roteiro de Analise por Uso). Os resultados mostraram ser possivel classificar as areas em “aptas” e “nao aptas” para determinado uso, permitindo com essa estrategia de organizacao identificar, quantificar e espacializar as areas em conformidade com limite de perda de solo potencial e apontar aquelas que nao toleram o uso testado, informacao util aos tomadores de decisao quando em estudos de planejamento regional. Methodological Strategy for Zoning by using Soil Loss Potential in a Watershed in southern Brazil ABSTRACT The aim of this study was to propose a methodological approach to determine the best land use based on USLE model parameters, using the watershed as planning unit. The model USLE parameters were spatialized using the software ArcGis 10.5, for the case study of the Cachoeira Cinco Veados watershed, RS-Brazil, and the erosive values were categorized according to the methodology of Ribeiro (2006). We reclassified the areas in “suitable” and “not suitable” to the tested use, according to two limit-criteria adopted as maximum acceptable soil losses (20 and 50 t ha -1 year -1 ). The methodology consists of constructing two strategies: the first is a construction of a thematic map, considering a priority order of uses in the watershed, where the most spendthrift use was analyzed first (Script of Hierarchical Analysis among Uses); and the second consists of the construction of maps that correspond to scenarios with watershed areas suitable to a given use, according to the classification criterion used, and their crossing with the current use map (Analysis Script by Use). The results show it is possible to classify the areas in “suitable” and “not suitable” for a given use, allowing with this organizational strategy to identify, quantify and spatialize the areas in accordance with the limit of potential soil loss and point out those that do not tolerate the tested use. This is a useful information for decision makers when studying regional planning. Keywords: Zoning; Watershed; Erosion; USLE.

In the last decades, the studies involving the mechanisms of the CO2 emissions dynamics have been studied in several ecosystems with varied soil classes. The objective of this study was to evaluate...

The soil position in the landscape reveals its formation history. Landscapes combine surface features and subsurface components (parent material) of the earth, at which the soil inserts as a three-dimensional and dynamic natural body. The present research aimed to study the soil–landscape relationship in a sandstone-gneiss topolithosequence and the factors determining soil diversification in the State of Amazonas, Brazil. The study extended along a transect of 9253 m, covering the distance between the first and the last profile, for a total of five profiles opened. Profile selection considered landscape topography, from the highest to the lowest relief of the terrain. Soil profiles characterization and classification were based on morphological, chemical, and physical properties and the mineralogy of the clay fraction by X-ray diffraction (XRD). Lithological contrasts and landscape variations determined the different soil types along the topolithosequence. Morphological, physical, chemical, and mineralogical attributes also varied along the landscape. The relief and the parent material, sandstone-gneiss, were the main factors influencing the pedogenesis. Goethite (5–40 g kg–1) was the predominant Fe oxide in all the soils, reflecting the low total iron content (Fet ≤ 68 g kg–1) of the soils and parent materials. The predominance of the sand fraction in all the studied profiles reflected the alluvial nature of the parent material, with the highest values (total sand > 800 g kg–1) occurring in the convex creep slope. Knowing the geomorphic surfaces and the parent material was effective for understanding the variation of the soil attributes along the landscape.

A região sul do estado do Amazonas vem sofrendo recentemente com a substituição de áreas de floresta por atividades agrícolas e pecuária. O avanço dessas atividades, sem levar em consideração as condições estruturais do solo, pode causar danos ao ambiente, podendo esgotá-los. O objetivo do estudo foi avaliar a dependência espacial da resistência à penetração e umidade em relação a profundidade do solo de Terra Preta Arqueológica sob cultivo de café Conilon no sul do estado do Amazonas. Foi delimitado uma malha amostral de 88x64 metros, com espaçamento regular de oito metros, perfazendo um total de 88 pontos amostrais. Nesses locais, foram coletadas amostras de solo nas profundidades de 0-5, 5-10 e 10-20 cm. Foram realizadas análises de textura, resistência a penetração do solo e umidade volumétrica. Os resultados das análises de solos foram submetidos à análise estatística clássica e espacial. Os resultados obtidos indicam que a resistência à penetração e umidade volumétrica do solo possuem moderada a forte dependência espacial nas profundidades de 0-5, 5-10 e 10-20 cm. O teor de água no solo afetou consideravelmente a variabilidade espacial da resistência à penetração; quanto menor o teor de água, menor foi a dependência espacial.

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.

Geostatistical and multivariate techniques have been widely used to identify and characterize the soil spatial variability, as well as to detect possible relationships between soil properties and management. Besides that, these techniques provide information regarding the spatial and temporal structural changes of soils to support better decision-making processes and management practices. Although the Zona da Mata region is a reference for sugarcane production in the northeast of Brazil, only a few studies have been carried out to clarify the effects of different management on soil physical attributes by using geostatistical and multivariate techniques. Thus, the objectives of this study were: (I) to characterize the spatial distribution of soils physical attributes under rainfed and irrigated sugarcane cultivations; (II) to identify the minimum sampling for the determination of soil physical attributes; (III) to detect the effects of the different management on soil physical attributes based on the principal component analysis (PCA). The study was carried out in the agricultural area of the Carpina Sugarcane Experimental Station of the Federal Rural University of Pernambuco, 7º51’13”S, 35º14’10”W, characterized by a Typic Hapludult with sandy clay loam soil texture. The investigated plot, cultivated with sugarcane, included a rainfed and an irrigated treatment in which a sprinkler system was installed according to a 12x12m grid. The interval between consecutive watering was fixed in two days, whereas irrigation depth was calculated to replace crop evapotranspiration (ETc) and accounting for the effective precipitation of the period. Daily ETc was estimated based on crop coefficient and reference evapotranspiration (ETo) indirectly obtained through a class A evaporation pan. In both treatments, the soil spatial variability was determined according to a 56x32m grid, on 32 soil samples collected in the 0.0-0.1m soil layer, spaced 7x8m, and georeferenced with a global position system. The soil was physically characterized according to the following attributes: bulk density (BD), soil penetration resistance (SPR), macroporosity (Macro), mesoporosity (Meso), microporosity (Micro), total porosity (TP), saturated hydraulic conductivity (Ksat), gravimetric soil water content (SWCg), geometric mean diameter (GMD) and mean weight diameter (MWD). The results of the descriptive statistics showed that among the studied attributes, Ksat, SPR, and Macro presented higher CV values, equal to 63 and 69%, 35 and 40%, and 32 and 44%, under rainfed and irrigated conditions, respectively. The minimum sampling, adequate to characterize the different soil attributes, resulted in general smaller in the rainfed area, characterized by higher homogeneity. Thus, the GMD, SWCg (both with 2 points ha-1), and SPR (with 6 points ha-1) were identified as the soil physical attributes requiring the lowest sample density; on the other hand, MWD and Ksat, with 14 and 15 points ha-1, respectively, required the highest number of samples. Pearson’s correlation analysis evidenced that soil BD was the most influential physical attribute in the studied areas, with a significant and inverse effect in most of the investigated attributes. The geostatistical approach associated with the multivariate PCA provided to understand the relationships between the spatial distribution patterns associated with irrigated and rainfed management and soil physical properties.

Studying particle size distribution is important to understand soil structure and formation processes. This research aimed to assess the fractal dimension of soil texture in Indian Dark Earth (IDE) areas in southern Amazonas state under different land uses, as follows: two areas in the municipality of Apuí, one growing cocoa and the other coffee; a grassland area in the municipality of Manicoré; and a forest area in the municipality of Novo Aripuanã. A sampling grid containing 88 collection points (intersecting points on the grid) was established in each area, measuring 80 x 42 m for the cocoa and coffee-growing sites, and 80 x 56 m and 60 x 42 m for the grassland and forest areas, respectively. Soil samples were collected in soil core and as clumps at a depth of 0.0-0.20m to determine the structural physical properties and texture of the soil. The following physical attributes were assessed: texture (PSD), bulk density (BD), macroporosity (Macro), microporosity (Micro), total porosity (TP) and aggregate stability (GMD and WMD). The fractal dimension (D) of the soil texture was determined, followed by analysis of variance and comparison of the means using Tukey’s test (p≤0.05). Pearson’s correlation was applied to assess the correlation between variables. There was a significant difference between the IDEs studied, with a higher D value in the cocoa-growing area in relation to the other sites. Additionally, the larger the clay fraction, the higher the D value. Fractal dimension (D) showed a positive correlation with sand, clay, BD, Macro, GMD and WMD, and a negative correlation with silt, micro, TP. Based on the D values obtained, the ADE cultivated with cocoa showed superior quality in relation to the other areas studied. Estudar a distribuição do tamanho das partículas é importante para entender a estrutura do solo e os processos de formação. Esta pesquisa teve como objetivo avaliar a dimensão fractal da textura do solo em áreas de Terra Preta de Índio (TPI) no sul do Estado do Amazonas sob diferentes usos da terra: duas áreas no município de Apuí, uma com cultivo de cacau e outra de café; uma área de pastagem no município de Manicoré; e uma área florestal no município de Novo Aripuanã. Uma malha de amostragem contendo 88 pontos de coleta (pontos de interseção na grade) foi estabelecida em cada área, medindo 80 x 42 m para as áreas de cacau e café, e 80 x 56 m e 60 x 42 m para as áreas de pastagem e floresta, respectivamente. Amostras de solo foram coletadas em torrões a uma profundidade de 0,0-0,20 m para determinar as propriedades físicas estruturais e a textura do solo. Os seguintes atributos físicos foram avaliados: textura, densidade do solo (DS), macroporosidade (Macro), microporosidade (Micro), porosidade total (PT) e estabilidade de agregados (DMG e DMP). Determinou-se a dimensão fractal da textura do solo (D), seguida da análise de variância e comparação das médias pelo teste de Tukey (p≤0,05). A correlação de Pearson foi aplicada para avaliar a correlação entre as variáveis. Houve uma diferença significativa entre as TPIs estudadas, com um maior valor D na área de cultivo de cacau em relação aos outros locais. Além disso, quanto maior a fração argila, maior o valor de D. A dimensão fractal (D) apresentou correlação positiva com areia, argila, DS, Macro, DMG e DMP, e correlação negativa com silte, micro, PT. Com base nos valores de D obtidos, as TPIs cultivadas com cacau apresentaram qualidade superior em relação às demais áreas estudadas.

Archeological Dark Earths (ADEs) are fertility soils that are notoriously superior to the vast majority of soils typical of the Amazon region. The study on ADEs has intensified due to the good characteristics presented by these soils, such as high concentration of nutrients (phosphorus, calcium, magnesium). In this sense, the aim of this study was to evaluate the spatial distribution of soil chemical attributes in an area of black archeological earth soil under cocoa cultivation in the municipality of Apuí (AM). The mapping of a 42 x 88 m mesh, with irregular spacing of 6 x 8 m, totaling 88 points, was carried out, and then soil samples were collected at depths of 0.0-0.05; 0.05-0.10; (pH, O.C, Sto C, (H+Al), P, K, Ca, Mg, SB, CEC and V%). Data were analyzed using descriptive and geostatistical statistics techniques. The mean and median values were adjusted to the near values, indicating normal distribution, while the soil chemical attributes were adjusted to the spherical and exponential semivariograms models. The majority of the attributes presented coefficient of variation (CV) between 12.1 and 60%, characterized as average variability, the variables in the study presented different ranges and most of them had a strong spatial dependence. The geostatistical techniques used allowed the adjustments of the theoretical models that best represented the experimental semivariance, thus enabling the construction of thematic maps of the spatial distribution of the values of the attributes of the studied area. © 2019, Universidade Federal de Uberlandia. All rights reserved.

Soil management, although intended to create favorable structural conditions for crop growth and development, without prior assessment of potential and limitations, has been one of the reasons for the degradation of natural resources. The effects on soil degradation and respective structural quality are generally evaluated by some physical soil attributes such as bulk density (BD), total porosity (TP) and soil penetration resistance (PR). The PR is recognized as a physical parameter that supports the identification of areas with different stages of compaction and thus can be used to define appropriate management for soil remediation. Besides, this parameter depends on intrinsic soil factors (texture, structure, and mineralogy) and soil water content (SWC). Therefore, PR increases with BD and decreases with SWC (gravimetric or volumetric). Thus, it is possible to establish the critical limit of PR (PRCL) associated with the value of SWC that limits the growth of plant roots. PRCL varies according to soil type and plant species, but 2.0 MPa is the value scientifically accepted as the critical value to limit the root growth. Thus, the paper aimed to evaluate the spatial and temporal variability of PR in a field cultivated with sugarcane, under the conventional tillage system. The research was carried out in the Carpina Sugarcane Experimental Station, Pernambuco, Brazil. A grid of 70 x 70 m was delineated at intervals of 10 m and in each point soil samples were collected in the layers 0 - 0.30 m and 0.30 - 0.60 m depth. Three samplings were done to determine gravimetric soil water content; the first after six months of subsoiling (Time 6) before harrowing and planting, the second after 12 months of subsoiling (Time 12, six months after harrowing and planting) and the last after 18 months of subsoiling, before harvesting (Time 18). In each sampling time, in situ PR tests were carried out with the Solo Track equipment (Falker® - Model PLG 5300) and the simultaneous values of gravimetric soil water content were determined and associated with the PR data. The results showed that soil water content had a weak degree of spatial dependence, indicating the need to increase the number of samples. On the other hand, the PR values showed that the subsoiling did not promote a positive effect on the soil physical quality, with values above the PRCL for root development in Time 6 (2.42 MPa), even if after one year the sugarcane root system acted positively, by reducing PR in Time 18 (1.04 MPa) below the critical value.

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).

Spatial mapping of soil chemical attributes is essential for sampling efficiency and agricultural planning management, ensuring a regional development and sustainability of the unique characteristics of archaeological black earths (ABEs). Thus, this study was developed aiming at assessing the spatial variability and sampling density of chemical attributes in soils of ABEs under pasture. A sampling grid of 56 × 80 m with regular spacings of 8 m was installed in the experimental area and samples were taken from the crossing points at depths of 0.0–0.05, 0.05–0.10, and 0.10–0.20 m, totaling 264 georeferenced points. The chemical attributes pH, OC, Ca, Mg, K, P, Al, and potential acidity were determined in these samples, while CEC, SB, V, t, T, and m were calculated. The attributes present a spatial dependence varying from strong to moderate, being Al3+ the only chemical attribute that does not present a spatial dependence structure in the assessed depths. Scaled semivariograms satisfactorily reproduce the spatial behavior of attributes in the same pattern of individual semivariograms. Sampling density is higher at a depth of 0.0–0.05 m. The decrease in the variability in the attributes in depth proves that the pasture management affects the soil more superficially.

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.

This article presents the identification of soil use potential for different agropastoral and forest scenarios, using an indicator for erosion susceptibility from the spatialized Universal Soil Loss Equation (USLE). All USLE factors were spatialized using ArcGis 10.5 software, for the case study of the Cachoeira Cinco Veados Watershed-RS. To determine the R factor, we used the Cassol et al. 2007 equation and a 33-year series of rain data from six climatic stations. For the K factor, published values for the soil classes: Entisol, Ultisol, Oxisol, Molisols were used. From the DEM, the LS factor was obtained, considering six slope classes (0-3, 3-8, 8-20, 20-45, 45-75, >75%). In addition to the actual land use situation in the watershed, nine scenarios were proposed for the C factor. The value of 0.5 was used for the evaluation of conservation practices (P factor). Considering scenarios of current use situation along with the nine other scenarios, the results showed that, by identifying the most susceptible areas in each scenario, it is possible to construct an indicator map of soil compatibilities for each use, considering sustainable limits of soil losses. Therefore, this resulting map has potential use as instrument for land use planning and zoning studies.

The soil and vegetation characteristics of the southern Amazonas region include highly weathered soils, high aluminum content and some hydromorphic conditions, its vegetation is composed from grasslands to small isolated trees and forest galleries along the rivers streams. In this way, this work aims to characterize and classify the soil in areas of clean field, dirty field, and forest in Humaitá region AM. Soil trenches were opened in the clean field, dirty field, and forest environments, soil profiles were morphologically characterized, and samples were collected from their horizons. Physical analysis of texture, dispersed clay in water, flocculation, bulk density, particle density and porosity were performed. The chemical analyzes included pH and KCl in water; Ca, Mg, K, Al, and; available P; H+Al and organic C; SiO2, Al2O3 and Fe2O3 sulfuric attack. The soils were classified according to criteria established by the Brazilian System of Soil Classification and Soil Taxonomy. The forest, dirty field (high) and clean field (low) showed different soil types, Typic Dystrudept for the first two environments and Typic Fluvaquents for last. Multivariate techniques expressed the similarity relations presenting between the different environments studied, characterizing, which are of great importance in the relation landscape-soil studies. As características do solo e da vegetação da região sul do Amazonas incluem solos altamente intemperizados, alto teor de alumínio e algumas condições hidromórficas, sendo sua vegetação composta por pastos, pequenas árvores isoladas e galerias florestais ao longo dos cursos d'água. Desta forma, este trabalho tem como objetivo caracterizar e classificar o solo em áreas de campo limpo, campo sujo e floresta na região de Humaitá AM. As valas foram abertas no campo limpo, no campo sujo e nos ambientes florestais, os perfis dos solos foram caracterizados morfologicamente e as amostras foram coletadas de seus horizontes. Análises físicas de textura, argila dispersa em água, floculação, densidade do solo, densidade de partículas e porosidade foram realizadas. As análises químicas incluíram pH e KCl em água; Ca, Mg, K, Al e; P disponível; H + Al e C orgânico; Ataque sulfúrico de SiO2, Al2O3 e Fe2O3. Os solos foram classificados de acordo com critérios estabelecidos pelo Sistema Brasileiro de Classificação de Solos e Taxonomia de Solos. A mata, o campo sujo (alto) e o campo limpo (baixo) apresentaram diferentes tipos de solo, distritos típicos para os dois primeiros ambientes e fluídicos típicos para o último. Técnicas multivariadas expressaram as relações de similaridade que se apresentam entre os diferentes ambientes estudados, caracterizando, que são de grande importância na relação paisagem-solo.

Spatial mapping of soil chemical attributes is essential for sampling efficiency and agricultural planning management, ensuring a regional development and sustainability of the unique characteristics of archaeological black earths (ABEs). Thus, this study was developed aiming at assessing the spatial variability and sampling density of chemical attributes in soils of ABEs under pasture in southern Amazonas, Brazil. A sampling grid of 56 × 80 m with regular spacings of 8 m was installed in the experimental area and samples were taken from the crossing points at depths of 0.0–0.05, 0.05–0.10, and 0.10–0.20 m, totaling 264 georeferenced points. The chemical attributes pH in water, organic carbon, Ca, Mg, K, P, Al, and potential acidity were determined in these samples, while CEC, SB, V, t, T, and m were calculated. The attributes present a spatial dependence varying from strong to moderate, being Al3+ the only chemical attribute that does not present a spatial dependence structure in the assessed depths. Scaled semivariograms satisfactorily reproduce the spatial behavior of attributes in the same pattern of individual semivariograms, allowing their use to estimate the variability of soil attributes. Sampling density is higher at a depth of 0.0–0.05 m, requiring 2 and 1 point ha−1 at depths of 0.05–0.10 and 0.10–0.20 m, respectively, to represent the spatial pattern of chemical attributes.

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.

A produção de grãos no estado do Amazonas ainda é incipiente para atender a demanda local por estes alimentos. Nesse contexto, foi realizado um experimento no município de Humaitá-AM com o objetivo de avaliar o desempenho agronômico de cultivares de arroz de terras altas. O trabalho foi conduzido em área de campo natural e o delineamento experimental foi em blocos ao acaso, com 12 tratamentos (cultivares de arroz) e 4 repetições. A semeadura foi realizada manualmente em 22/11/2011 no espaçamento de 0,20 m entre linhas e densidade de 60 sementes por metro. Foram realizadas 2 adubações de cobertura, a primeira na fase de perfilhamento e a segunda na fase de diferenciação do primórdio floral. A colheita foi realizada manualmente quando os grãos apresentaram em torno de 22% de umidade. Os cultivares apresentaram redução no número de dias para atingir floração média e ciclo, o cultivar BRS Tropical apresentou menor altura, os cultivares BRS Apinajé, BRS Primavera e BRSMG Curinga obtiveram maior altura de planta. A maior produtividade e rendimento de grãos foram observados no cultivar BRSGO Serra Dourada, juntamente com os cultivares BRS Sertaneja, BRS pepita e BRS Tropical. Os cultivares BRSGO Serra Dourada, BRS Sertaneja, BRS Pepita e BRS Tropical podem ser considerados promissores para região, devido ao bom desempenho produtivo nas condições de cultivo. A análise multivariada mostrou de forma excelente as correlações existentes entre as variáveis.

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.

A agregação do solo pode representar um parâmetro que relaciona o manejo à qualidade do solo para às terra preta arqueológica (TPA). O objetivo do trabalho foi estudar a variabilidade espacial dos agregados e matéria orgânica do solo em terra preta arqueológica sob pastagem. Os dados foram coletados em uma grade amostral com as dimensões de 80 x 56 m, com espaço entre os pontos de 08 m, e total de 88 pontos amostrais. As amostras de solos foram coletadas nas profundidades 0,0-0,05, 0,05-0,10 e 0,10-20 m, para as avaliações: diâmetro médio geométrico (DMG), classe de agregados > 2,00mm, 2-1 mm, índice da estabilidade dos agregados (IEA) e matéria orgânica do solo (MO); após análise exploratória e geoestatística, os modelos foram ajustados aos semivariogramas para cada atributo. Os resultados mostraram que a porcentagem de agregados na classe > 2,00 mm apresentou valores acima de 80% indicando maior resistência à desagregação. Os altos teores de MO no solo influenciaram a formação e estabilização dos agregados do solo.

A implantação de atividades florestais, agrícolas e pecuária vem modificando a cobertura vegetal original de grande parte do território brasileiro. Ecossistemas naturais, como o cerrado e a floresta amazônica, vêm perdendo suas características originais e cedendo lugar para essas atividades. O objetivo foi avaliar os atributos do solo sob diferentes usos na fazenda Santa Rita, em Humaitá, Amazonas no período de 2012 a 2013. O solo foi classificado como Cambissolo Háplico Alítico plíntico. Foram selecionadas três áreas: área de pastagem abandonada, área de agricultura abandonada e área de campo nativo, com vegetação nativa. Em cada sistema de uso, foi demarcada uma área de 60 × 80 m, com 12 pontos amostrais, e os solos foram coletados nas camadas de 0,00 - 0,05 m e 0,05 - 0,10 m, com estrutura preservada, totalizando, assim, 24 amostras por sistema de uso. Realizaram-se as seguintes análises físicas: textura, macroporosidade, microporosidade, porosidade total, umidade volumétrica do solo, densidade do solo, estabilidade de agregados. Realizaram-se as seguintes análises químicas: pH em água, acidez potencial, alumínio trocável, carbono orgânico e estoque de carbono. Para a análise dos dados, foram utilizadas as estatísticas univariada e multivariada. A substituição da vegetação nativa por sistemas de usos ocasionou alterações nos atributos físicos e químicos do solo. O uso das técnicas multivariadas mostrou-se eficiente na distinção de ambientes sobre os sistemas de usos estudados.

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.