Sampling density and proportion for the characterization of the variability of Oxisol attributes on different materials

et al. 2018

CATENA

This study aimed to use spatial uncertainty of magnetic susceptibility (MS) and clay content to improve soilmapping units. In an experimental area of 870 ha, a regular sampling grid containing 371 points was set, in which MS and clay content were assessed at a depth range of 0-0.25 m. Using a digital elevation model and field observations, a 4440-m transect was established on the study area from hilltop to the foothill, toward the gentlest slope. Standard deviation maps based on 200 realizations of the sequential gaussian simulation measured spatial estimate uncertainties. To limit transition zones along the transect, uncertainty isolines representative of the transition between soil-mapping units were selected. Both attributes presented peaks of uncertainties near the change of mapping units, previously known. Uncertainty zones, previously delineated, ranged from 45 to 210 m and from 60 to 170 m, for MS and clay content, respectively. However, after extrapolating the uncertainties to the side of the transect, amplitude changes of the uncertainty zones were observed, especially in the transition regions between landscape shape and geology. Delineation of mapping units, which incorporated the uncertainties of MS and clay content, was similar. However, due to lower cost and promptness, MS becomes the most feasible alternative. Knowing spatial uncertainties enables readjusting limits in maps of soil-mapping units and may support identification of most favorable regions for determining modal pedon representative of each unit.

Section: Resultssupporting

confidence: 84%

Section: Resultsmentioning

confidence: 99%

Mapping units based on spatial uncertainty of magnetic susceptibility and clay content

Teixeira

Marques

et al. 2018

CATENA

“…Additionally, studies on the characterization of the spatial variability of fCO 2 can also be drawn from these results in order to help establish the proportion in samples of MS ADS to fCO 2 , as developed for MS ADS and clay content by Siqueira et al (2014). This information may assist further studies and clarify the relationship between landscape use and global climate changes by providing information to support decisions about mitigation and adaptation strategies (Bayer et al, 2006;De Figueiredo and La Scala, 2011).…”

Section: Discussionmentioning

confidence: 99%

Characterization of potential CO2 emissions in agricultural areas using magnetic susceptibility

Leal

França

Sci. agric. (Piracicaba, Braz.)

et al. 2015

Soil CO 2 emissions (fCO 2 ) in agricultural areas have been widely studied in global climate change research, but its characterization and quantification are restricted to small areas. Because spatial and time variability affect emissions, tools need to be developed to predict fCO 2 for large areas. This study aimed to investigate soil magnetic susceptibility (MS) and its correlation with fCO 2 in an agricultural environment. The experiment was carried out on a Typic Eutrudox located in Guariba-SP, Brazil. Results showed that there was negative spatial correlation between fCO 2 and the magnetic susceptibility of Air Dried Soil (MS ADS ) up to 34.3 m distant. However, the fCO 2 had no significant correlation with MS ADS , magnetic susceptibility of sand (MS SAND ) nor clay (MS CLAY ). However, MS ADS could be a supplemental mean of identifying regions of high fCO 2 potential over large areas.

“…Due to the high relationship between magnetic susceptibility and physical, chemical, and mineralogical attributes of the soil -identified by linear correlations (Siqueira et al, 2010a;Camargo et al, 2014;Siqueira et al, 2014) or by the similarity between range values in the semivariograms or by the error in the representation of the spatial variability structure (smaller C 0 value) -, magnetic susceptibility can be used to improve the identification of boundaries between soil areas in the field. In addition, the lower cost in magnetic susceptibility determination allows analyzing a higher number of samples than in the conventional analyses.…”

Section: Resultsmentioning

confidence: 99%

Magnetic susceptibility for characterizing areas with different potentials for sugarcane production

Júnior

Teixeira

et al. 2016

Pesq. agropec. bras.

-The objective of this work was to evaluate the use of magnetic susceptibility for characterizing the spatial variability of soil attributes and identifying areas with different potentials for sugarcane (Saccharum spp.) production. Samples were collected at 110 points (1 per 7 ha) in the layers of 0.00-0.20 and 0.20-0.40 m, to determine the magnetic susceptibility and physical and chemical attributes of the soil. Fiber content, sucrose polarization (POL), and sugarcane yield were determined in 33 points. The spatial variability model for magnetic susceptibility was 63 and 22% more accurate in delimiting soil potential for sugarcane production than soil physical and chemical attributes at the 0.0-0.2 and 0.2-0.4-m layers, respectively. The spatial variability map for magnetic susceptibility was strongly correlated with clay (0.83 and 0.89, respectively, for the layers) and sand contents (-0.84 and -0.88); moderately correlated with organic matter (-0.25 and -0.35), sum of bases (-0.46 and 0.37), cation exchange capacity (0.22 and 0.47), pH (-0.52 and 0.13), and POL (0.43 and 0.53); and weakly correlated with sugarcane yield (0.26 and 0.23). Magnetic susceptibility can be used to characterize the spatial variability of soil attributes and to identify areas with different potentials for sugarcane production.Index terms: detailed mapping, geostatistics, indirect quantification, pedometrics, scaled semivariogram, spatial correlation. Susceptibilidade magnética para a caracterização de áreas com diferentes potenciais de produção de cana-de-açúcarResumo -O objetivo deste trabalho foi avaliar o uso da susceptibilidade magnética para caracterizar a variabilidade espacial dos atributos do solo e identificar áreas com diferentes potenciais de produção de cana-de-açúcar (Saccharum spp.). Foram coletadas amostras em 110 pontos (1 por cada 7 ha), nas camadas de 0,00-0,20 e 0,20-0,40 m, para determinação da suscetibilidade magnética e de atributos físicos e químicos do solo. O teor de fibra, a polarização da sacarose (POL) e a produtividade da cana-de-açúcar foram determinados em 33 pontos. O modelo de variabilidade espacial da susceptibilidade magnética foi 63 e 22% mais acurado em delimitar o potencial do solo para produção da cana-de-açúcar que os atributos físicos e químicos do solo, nas camadas de 0,00-0,20 e de 0,20-0,40 m de profundidade, respectivamente. O mapa da variabilidade espacial da susceptibilidade magnética apresentou forte correlação com o conteúdo de argila (0,83 e 0,89, respectivamente, para as camadas) e de areia (-0,84 e -0,88); moderada correlação com a matéria orgânica (-0,25 e -0,35), a soma de bases (-046 e 0,37), a capacidade de troca catiônica (0,22 e 0,47), o pH (-0,52 e 0,13) e a POL (0,43 e 0,53); e fraca correlação com a produtividade da cana-de-açúcar (0,26 e 0,23). A susceptibilidade magnética pode ser utilizada para caracterizar a variabilidade espacial dos atributos do solo e para identificar áreas com diferentes potenciais para produção de cana-de-açúcar.Termos para indexação: mape...