VARIABILIDADE ESPACIAL DA CONDUTIVIDADE HIDRÁULICA DO SOLO SATURADO EM LATOSSOLO AMARELO DISTROCOESO, NO MUNICÍPIO DE CRUZ DAS ALMAS KARLA SILVA SANTOS ALVARES DE ALMEIDA1; LUCIANO DA SILVA SOUZA1; VITAL PEDRO DA SILVA PAZ1; FAGNER TAIANO DOS SANTOS SILVA2; DAVI NEY SANTOS1 E JULIANA DA SILVA LOPES PEREIRA1 1Universidade Federal do Recôncavo da Bahia – UFRB, Rua Rui Barbosa, 710 – Campus Universitário – CEP 44380-000 – Cruz das Almas – BA, e-mail: karlasilvasantos@yahoo.com.br; lsouza@ufrb.edu.br; vitalpaz@ufrb.edu.br; davineysantos@gmail.com; jslpereira@hotmail.com2Universidade do Estado de Santa Catarina – UDESC, Centro de Ciências Agroveterinárias – CAV, Av. Luiz de Camões, 2090 – CEP 88520-000 - Lages – SC, e-mail: ftssilva.ufrb@gmail.com 1 RESUMO O objetivo desse trabalho foi caracterizar a variabilidade espacial da condutividade hidráulica do solo saturado (K0) utilizando dois métodos de laboratório e amostras com diferentes volumes em Latossolo Amarelo Distrocoeso localizado no Município de Cruz das Almas. Foram coletadas amostras com estrutura indeformada em dois tipos de anéis volumétricos com 0,081 m de altura e 0,070 m de diâmetro (≈312 cm3) e com 0,05 m de altura e de diâmetro (98 cm3). Nos mesmos pontos de amostragem da K0 foram coletadas amostras deformadas para quantificação de areia, silte, argila, porosidade total, macro e microporosidade, densidade do solo em uma malha amostral de 7 x 7 pontos espaçados em 2,0 x 2,0 m, totalizando uma área de 196,0 m². Os resultados foram submetidos à análise estatística exploratória e teste de normalidade de Shapiro-Wilk; posteriormente, verificou-se a dependência espacial pela análise geoestatística. Os resultados revelaram que para a profundidade de 0-0,15 m a condutividade hidráulica determinada no permeâmetro de carga constante no cilindro de volume maior apresentou menor coeficiente de variação, indicando uma melhor representatividade das amostras; a densidade do solo apresentou índice de dependência espacial moderada, com alcance de 1,22 m e semivariograma tipo esférico para a profundidade de 0-0,15m; para a profundidade de 0,15-0,30 o índice de dependência espacial foi forte, com alcance de 1,54 m e semivariograma tipo exponencial. Palavras-chave: condutividade hidráulica saturada, Tabuleiro Costeiro, geoestatística. ALMEIDA, K. S. S. A.; SOUZA, L. S.; PAZ, V. P. S.; SILVA, F. T. S.; SANTOS, D. N.; PEREIRA, J. S. L.SPATIAL VARIABILITY OF HYDRAULIC CONDUCTIVITY OF SATURATED SOIL USING TWO LABORATORY METHODS AND SAMPLES WITH DIFFERENTS VOLUMES 2 ABSTRACT The objective of this work was to characterize the spatial variability of saturated hydraulic conductivity (K0) using two laboratory methods and samples with different volumes in Oxisoil Distrocoeso located in the city of Cruz das Almas. Deformed structural samples were collected in two types of volumetric rings with 0.081 m long and 0.070 m in diameter (312 cm3) and 0.05 m in height and diameter (98 cm3). In the same sampling points of K0 deformed samples were collected for quantification of sand, silt, clay, total porosity, macro and microporosity, bulk density in a sample grid of 7 x 7 points spaced at 2.0 x 2.0 m totaling an area of 196.0 m². The results were submitted to exploratory statistical analysis and Shapiro-Wilk normality test; later, the spatial dependence was verified by geostatistical analysis. The results showed that for the depth of 0-0.15 m the hydraulic conductivity determined in the constant load permeameter in the higest volume cylinder showed a lower coefficient of variation, indicating a better representativeness of the samples; soil bulk density showed moderate spatial dependence index, with a range of 1.22 m and pherical-type semivariogram to the depth of 0-0.15m; to the depth of 0.15-0.30 the spatial dependence index was strong, reaching 1.54 m and exponential semivariogram. Keywords: Saturated hydraulic conductivity, coastal plain, geostatistics
Cohesive Oxisols are widely used for cultivating eucalyptus in the Coastal Tablelands of the northeastern region of Brazil. However, mechanization and plant cultivation in these soils are difficult because of their cohesive layers. Therefore, the objective of this study was to identify better combinations between tillage systems and types of fertilization to improve the physical attributes of cohesive soil, with the aim of improving eucalyptus growth. The experimental design was completely randomized in a 4 × 2 factorial scheme (soil preparation × fertilization). The tillage systems tested were: i) conventional tillage (CT) - one plowing combined with two harrowings, ii) minimum tillage (MT) - subsoiling down until 0.57 m depths in the planting line, iii) no-tillage type 1 (NT1) - planting in 0.3 m-deep pits, and iv) no-tillage type 2 (NT2) - planting in 0.6 m-deep pits. The types of fertilization tested were mineral (MF) and organic fertilization (OF). The diameter of the soil aggregates was reduced after being subjected to any combination of cohesive soils. Furthermore, OF provided the best levels of plant-available water, attenuating the adverse conditions of the cohesive layer. MT, NT1, and NT2 improved the soil physical attributes when compared to CT. Therefore, the combination of either NT1 or NT2 with OF, followed by the combination of either NT1 or NT2 with MF, was determined to be the best way to cultivate eucalyptus on cohesive soils.
ResumoO avanço do conhecimento da variabilidade espacial dos atributos do solo, por meio do uso de ferramentas da agricultura de precisão e geoestatística, tem sido considerado como uma estratégia de manejo que visa maximizar a produtividade agrícola. Objetivo foi avaliar a eficiência de malhas amostrais na caracterização da variabilidade espacial dos atributos físicos do solo na cultura do fumo. O trabalho foi desenvolvido na Fazenda Capivari, no município de Governador Mangabeira, Bahia. Avaliou-se: resistência do solo à penetração de raízes e condutividade hidráulica em duas malhas regulares, de 15x15 e 25x25 m, georreferenciadas. A resistência à penetração foi avaliada mediante o uso de penetrômetro de impacto. A determinação da condutividade hidráulica foi realizada por meio de ensaios em permeâmetro de carga constante. Os valores de resistência à penetração da malha 1 (15x15m) concentraram-se na faixa de pouca limitação a penetração de raízes, enquanto que na malha 2 (25x25m) no perfil abaixo dos 0,40 m valores superiores a 2,6 MPa, o que já implica em algumas limitações à penetração de raízes. Os dados demonstram que a malha amostral de maior dimensão apresenta grande potencial em detectar diferentes escalas de variabilidade espacial dos atributos físicos avaliados em Latossolos sob cultivo de fumo. Palavras-chave: Compactação do solo; condutividade hidráulica; fumo AbstractThe improvement in the knowledge of the spatial variability of soil attributes through the use of precision agriculture and geostatistics tools, have been considered as a management strategy to maximize agricultural productivity. The aim of this study was to evaluate the efficiency of sample meshes in characterizing the spatial variability of soil physical attributes in the tobacco crop. The work was developed at Fazenda Capivari, in the municipality of Governador Mangabeira, Bahia. It was evaluated: soil resistance to root penetration and hydraulic conductivity in two regular meshs, 15x15 and 25x25 m, georeferenced. The penetration resistance was evaluated using an impact penetrometer. The determination of hydraulic conductivity was made by means of constant load permeability tests. The values of resistance to penetration by the mesh 1 (15x15m) were concentrated in the range of little limitation to root penetration, whereas in the mesh 2 (25x25m) in the profile below 0,40 m values greater than 2,6 MPa, the Which already implies in some limitations to the roots penetration. The data demonstrated that the larger sampling mesh shows great potential in detecting different scales of spatial variability of the physical attributes evaluated in Oxisols under tobacco cultivation
Consolidation tests give important insights into soil compactibility. However, it requires equipment that is not always available. The costal tablelands in Northeastern Brazil have extensive areas of cohesive soils where compaction is an expressive problem. This region is a prominent producer of food and fibers with cassava as one of the leading products. Part of the cassava is used for flour production, generating wastewater, which is often applied as organic fertilizer to the soil. This can affect the compaction properties of soil due to its dispersing-flocculating characteristics. Uniaxial-compression tests and mathematical models are the primary methods to measure or estimate soil compaction. This study measured soil compression with a centrifuge, seeking a simple-quick method. We used specific loads (stainless-steel cylinders: mass) and increasing G-force (weight) to simulate the pressure on the samples used in most consolidation apparatus. Soils, sampling layers, and the presence of cassava wastewater (manipueira) were also compared since they may affect compactibility-related attributes. Samples of a Gray Cohesive Argisol and Dystrocohesive Yellow Latosol (depths of 0-0.20 m and 0.20-0.40 m) from the Tablelands of the state of Bahia, Brazil, were used. Wastewater affected water-dispersible clay, aggregate stability, pH, ∆pH, flocculation, and organic carbon, thus influencing compactibility but not the moisture and maximum density measured by the Proctor test. Centrifugation caused lower density than the Proctor test. The results were close to those estimated by the mathematical models, thus considered a promising alternative to estimating consolidation. This method also provides insight into the root growth-limiting density and the moisture content that leads to it.
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