No abstract

A variabilidade espacial dos atributos físicos do solo tem sido alvo de diversos estudos nos últimos anos. No entanto, pouco tem sido estudado sobre as diferenças de medidas entre os diversos métodos de amostragem. Desta maneira, este trabalho teve como objetivo analisar a variabilidade espacial de atributos físicos do solo determinados por diferentes métodos de amostragem de um Latossolo Vermelho eutroférrico, em Campinas (SP), Brasil, amostrado de janeiro a maio de 2005 em 302 pontos com espaçamento de 10 x 10 metros. A densidade do solo foi determinada por meio do método do anel volumétrico e do método do torrão impermeabilizado. A porosidade total do solo foi medida utilizando-se anéis volumétricos e calculada por meio da densidade de partículas de 2,65 kg dm -3 comumente descrita na literatura científica para solos minerais e de 2,84 kg dm -3 encontrada na área de estudo. A umidade do solo foi obtida por meio do método volumétrico, do método gravimétrico e pela técnica de reflectometria de domínio do tempo (TDR). A densidade obtida com anéis volumétricos apresentou o menor valor de coeficiente de variação (CV) e de efeito pepita (C 0 ), respectivamente, de 7,13% e 0,005. A porosidade total medida foi o método mais prático para avaliação deste atributo do solo. A umidade amostrada com anéis volumétricos revelou os valores mais próximos da média quando comparada aos demais métodos de amostragem do conteúdo de água no solo.Palavras-chave: densidade global, espaço poroso, conteúdo de água, geoestatística. ABSTRACT VARIABILITY OF SOIL PHYSICAL ATTRIBUTES DETERMINED BY DIFFERENT METHODSThe spatial variability of soil physical attributes has been the focus of many studies in the last few years. However, little has been discussed of differences of these attributes due to sampling methods. The objective of this study was to analyze the spatial variability of soil physical attributes sampled by different methods in Rhodic Eutrudox, in Campinas (SP, Brazil). Sampling was performed between January and May of 2005, at 302 points of a 10 x 10 m grid. Soil bulk density was measured by the volumetric soil core and the clod methods. Total soil porosity was estimated using the relation between soil bulk density and particle density 2,65 kg dm -3 described in scientific literature for mineral soil and 2,84 kg dm -3 found in the study area. Soil water content was measured by the volumetric core, gravimetric and TDR methods. Bulk density measured soil core presented the lesser value of coefficient of variation (CV) and effect nugget (C 0 ), respectively 7,13% and 0,005. The measured total porosity is presented as the method most practical for determination of this attribute of the soil. The humidity sampling volumetric presented results close to the overall average comparative to the too much methods of sampling of the soil water content.

The spatial variability of soil properties can be best characterized through concepts of scale invariance, fractals, and multifractals. The objectives of this study were to analyze and to compare the scaling patterns and structural heterogeneity of soil properties across two transects in Campinas, SP, Brazil, using the multifractal formalism. Two transects were marked parallel and perpendicular to land slope, with a length of 2.28 and 1.98 km, respectively. Soil samples were collected at the 0 to 20 cm depth every 30 m. The soil properties analyzed were: texture (sand, silt, clay), pH (H2O and KCl), organic carbon (OC) content, exchangeable Ca, H, and Al, exchangeable bases (SB), cation exchange capacity (CEC), and percent base saturation (V). Spatial variability of soil properties was controlled by natural causes, including parent material and topography, and by soil use and management. The variability of pH across the two transects was characterized by either quasi‐monofractal behavior or by a relatively low degree of multifractality. The other soil properties studied showed stronger degrees of multifractality. Hence, the multifractality for OC and silt content was much higher at the transect perpendicular to land slope. Variables from the soil exchange complex, particularly exchangeable Al, Ca, and SB, were characterized by higher multifractal indices in the two transects. Patterns of spatial distribution assessed by multifractal analysis were linked to soil forming factors and processes. Our results suggest that scale heterogeneity in the spatial distribution of soil properties was enhanced by the interaction of various natural or anthropogenic sources of variability.

A variabilidade espacial dos atributos físicos e químicos do solo possui relação direta com a formação e manutenção dos seus agregados. No entanto, os sistemas de manejo do solo também interagem com esses atributos modificando sua variabilidade natural, e consequentemente, a variabilidade do estado de agregação do solo. Assim, este trabalho teve como objetivo estudar a variabilidade espacial de atributos físicos e químicos de dois Latossolos do Estado de São Paulo, sob o sistema de semeadura direta e sua relação com a estabilidade de agregados. As amostras de solo foram coletadas na camada de 0,0 - 0,1 m, utilizando grade de amostragem de 100 m entre pontos. Uma das áreas está localizada no município de Angatuba (SP) e outra no município de Campos Novos Paulista (SP). Os atributos físicos analisados foram: argila, areia grossa, areia fina, areia total e a estabilidade de agregados avaliada por meio do diâmetro médio ponderado dos agregados (DMP). Os atributos químicos estudados foram: matéria orgânica, cálcio e magnésio. Os dados foram analisados por meio da estatística descritiva e de ferramentas geoestatísticas. Uma vez detectada a variabilidade espacial por meio do semivariograma, foram construídos mapas de isolinhas utilizando-se a técnica de interpolação por krigagem. A variabilidade espacial para os atributos físicos e químicos e sua relação com a estabilidade de agregados foi influenciada pelo histórico de manejo das áreas de estudo. Observaram-se valores mais baixos de efeito pepita (C0), quando comparados aos demais atributos estudados, Latossolo em Campos Novos Paulista. O espaçamento utilizado no Latossolo em Campos Novos Paulista não foi suficiente para detectar a dependência espacial do DMP.

Geostatistics allows the evaluation of the distribution pattern of data with high spatial variability in agricultural systems. This study aimed to evaluate the spatial variability of biological diversity indices of soil fauna under different land (agriculture and forest). Samples were collected in seven areas (millet, soybean, corn, eucalyptus, pasture crops, and preserved and disturbed Cerrado), in Maranhão state, Brazil. The soil fauna was caught trapped in pitfall traps, installed 3 m away from each other. In each area, 130 traps were maintained for seven days. After this period, they were removed and their content transferred to bottles and taken to the laboratory, where the insects were screened and identified at the level of orders and families. Eight indices were calculated, namely: individuals trap-1 day-1 , Jackknife richness estimator, the Simpson, McIntosh, Shannon, and total diversity, and Simpson dominance, and Pielou equitability indices. The spatial variability was derived from the semivariograms fitted to Gaussian, spherical, and exponential geostatistical models. Statistical analysis showed medium values of the coefficient of variation for millet, except for the indices individuals trap-1 day-1 and McIntosh diversity, which were considered high. The values of the correlation matrix were negative for some indices, suggesting an inverse relationship. For millet, corn, eucalyptus, disturbed Cerrado, and pasture areas, the Shannon diversity index exhibited a pure nugget effect. For the areas of millet, corn, disturbed Cerrado and pasture, the total diversity index was adjusted to the Gaussian model. The degree of spatial dependence was considered high for the individuals trap-1 day-1 and Pielou equitability indices for millet. Only for soybean and pasture similarity in the scaled semivariograms was observed for the spatial variability of the indices, indicating similarity of performance. Soil management and land use affect the patterns of soil fauna abundance, richness, and diversity. The presence of groups such as Araneae, Diplura, and Poduromorpha are related to ecological equilibrium, quality, and sustainability of the agricultural systems studied.