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Fator de Reflectância na Determinação da Matéria Orgânica em Latossolos em Morro do Chapéu-Ba
Abstract
The organic matter is a component of the soil that
performs functions like aeration, infiltration, humidity
and influence in the texture. The climatic and water
conditions, along with the different use and cover, alter
the morphological characteristics of the soil; with this, it
is necessary to understand the processes inherent to the
spectral behavior of the soils, with the use of clean
techniques that every day gain notoriety such as
reflectance spectroradiometry. With the objective of
evaluating the reflectance factor in the determination of
organic matter by spectroradiometry (400 - 2500 nm) of
Latossolo in Morro do Chapéu-BA. Two profiles of
Latosol were selected with chemical and spectral data
that were correlated to the soil use and cover data of the
studied area. Demonstrating that the physical-chemical
factors of the soil influence the spectral behavior and the
texture is an important indicator.
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The premise that guides this work is to discriminate, from reflectance measurements obtained in the laboratory, the chemical attributes of the same type of soil in three experimental areas of the Embrapa at systems of distinct management and land use. The systems of use and management of the soils are: organic mango crop, Caatinga degraded and Caatinga preserved. Thus, it is expected that the soil characteristics can be estimated by differences at reflected energy. From the spectral analysis was possible to identify the attributes existing in the samples because the absorption bands which varied in breadth and depth, but not in placement.In part, this can be attributed to organic matter that directly affects the biological characteristics of the soil acting as a carbon source, energy and nutrients for microorganisms and is significantly correlated with the intensity of reflectance across the spectrum. Thus, from the spectra, it was found that the content of organic matter is higher in the savanna preserved because it has a lower reflectance, while the cultivation of organic mango has a higher reflectance consequently a lower content of organic matter. This research aims to assist the technical progress of agriculture as the basis for planning without affecting the environmental aspects. Palavras-chave: reflectance, reflected energy, chemical attributes, reflectância, energia eletromagnética, atributos químicos.
Several methods exist for determining soil organic carbon, and each one has its own advantages and limitations. Consequently, a comparison of the experimental results obtained when these methods are employed is hampered, causing problems in the comparison of carbon stocks in soils. This study aimed at evaluating the analytical procedures used in the determination of carbon and their relationships with soil mineralogy and texture. Wet combustion methods, including Walkley-Black, Mebius and Colorimetric determination as well as dry combustion methods, such as Elemental and Gravimetric Analysis were used. Quantitative textural and mineralogical (kaolinite, goethite and gibbsite) analyses were also carried out. The wet digestion methods underestimated the concentration of organic carbon, while the gravimetric method overestimated. Soil mineralogy interfered with the determination of carbon, with emphasis on the gravimetric method that was greatly influenced by gibbsite.
Na Bacia Hidrográfica Água Fria, em Barra do Choça (BA), o desenvolvimento da lavoura cafeeira e da pastagem tem sido feito mediante a supressão da vegetação nativa, inclusive em áreas de proteção ambiental. O objetivo deste trabalho foi avaliar os atributos físicos: granulometria, argila dispersa em água, grau de floculação, diâmetro médio ponderado e índice de estabilidade de agregados e C orgânico dos solos submetidos a diferentes tipos de uso da terra na referida bacia. Para as amostragens, foram selecionadas seis glebas: duas de café (cultivo mecanizado e não mecanizado), duas de pastagens e duas de matas nativas, empregadas como referência. Constatou-se que o uso da terra diminuiu a estabilidade de agregados, evidenciada pela redução no diâmetro médio ponderado, pelo aumento dos agregados de menor tamanho e pelos menores teores de C orgânico na seqüência mata-pastagem-cafezal.In the watershed Água Fria, in Barra do Choça (BA), native vegetation and environmentally protected areas have been replaced by coffee and pasture cultivation. This study evaluated the physical characteristics, particle size distribution, water dispersible clay, flocculation, mean weight diameter and aggregate stability index and organic C concentration of soils under different land uses, in the area surroundings the above watershed. Soil samples were collected from six different fields: two coffee plantations (manual and mechanical cultivation), two pastures and two native forest areas were used as references. The different land uses reduced the aggregate stability, as indicated by the reduction of the mean weight diameter, increase of small-sized aggregates and lower organic C contents, in the order forest > pasture > coffee plantation.
The objective of this study was to test the teaching of some radiometric concepts, as well as a study case about reflectance factor of ten soil classes from São Paulo State, Brazil. The methodology applied for the development of this study was laboratory radiometry and full participation of all students in the entire experiment. The pedagogical results obtained were considered excellent in function of the approaches and discussions realized by the student involved.
A reflectância espectral de solos é a expressão que registra o fluxo de radiação eletromagnética refletida pelo solo em relação ao fluxo radiante. Como os solos apresentam diferentes constituintes, os mesmos podem ser identificados e em certos casos quantificados pela análise de sua resposta espectral. Os principais constituintes dos solos que influenciam seu comportamento espectral são a matéria orgânica, óxidos de ferro, argilominerais, além da distribuição granulométrica e umidade. A utilização da reflectância espectral visando obter informações na identificação e quantificação de características do solo de maneira rápida e não invasiva, tanto em nível laboratorial como em nível orbital, tem ocorrido principalmente em países desenvolvidos. No Brasil, o interesse de pesquisadores pelo estudo do comportamento espectral de solos vem crescendo desde a década de 80 do século passado, sendo esta linha de pesquisa relativamente jovem e necessitada de suporte de pesquisa para melhor entendimento dos efeitos da interação da energia eletromagnética entre os diferentes componentes do solo.
The influence of organic matter and amorphous and crystalline iron contents on the reflectance (400 to 2500 nm) of various soils was evaluated. Studied soils were Typic Argiudoll (TR), Typic Eutrorthox (LR), Typic Argiudoll (PE), Typic Haplortox (LE), Typic Quartzipsamment (AQ), and Typic Paleudalf (PV). Surface and subsurface soil samples were used in four conditions: a) as sampled; b) after removal of organic matter; c) after removal of the organic matter and the amorphous iron; and d) after removing organic matter and amorphous iron and crystalline iron. Reflectance factor was acquired from 400 nm to 2.450 nm and TM/Landsat spectral bands were simulated. Removal of organic and amorphous iron caused an overall increase of the reflectance along the spectrum, for all soils. Removal of crystalline iron caused the reflectance to increase in the first portion of the spectrum (400 to 1.000 nm), but not in intermediate (1.000 to 1.900 nm) and final portion of the spectrum (after 1.900 nm). Crystalline iron was responsible for concavities in the spectral region near 400 nm and 850 nm. Use of laboratory spectroradiometry proved to be a fast, non-destructive, and easy-to-prepare technique for analyzing absorption features caused by organic matter and iron forms in soils.
Efficient and effective modelling methods to assess soil organic carbon (SOC) stock are central in understanding the global carbon cycle and informing related land management decisions. However, mapping SOC stocks in semi-arid rangelands is challenging due to the lack of data and poor spatial coverage. The use of remote sensing data to provide an indirect measurement of SOC to inform digital soil mapping has the potential to provide more reliable and cost-effective estimates of SOC compared with field-based, direct measurement. Despite this potential, the role of remote sensing data in improving the knowledge of soil information in semi-arid rangelands has not been fully explored. This study firstly investigated the use of high spatial resolution satellite data (seasonal fractional cover data; SFC) together with elevation, lithology, climatic data and observed soil data to map the spatial distribution of SOC at two soil depths (0–5 cm and 0–30 cm) in semi-arid rangelands of eastern Australia. Overall, model performance statistics showed that random forest (RF) and boosted regression trees (BRT) models performed better than support vector machine (SVM). The models obtained moderate results with R2 of 0.32 for SOC stock at 0–5 cm and 0.44 at 0–30 cm, RMSE of 3.51 Mg C ha−1 at 0–5 cm and 9.16 Mg C ha−1 at 0–30 cm without considering SFC covariates. In contrast, by including SFC, the model accuracy for predicting SOC stock improved by 7.4–12.7% at 0–5 cm, and by 2.8–5.9% at 0–30 cm, highlighting the importance of including SFC to enhance the performance of the three modelling techniques. Furthermore, our models produced a more accurate and higher resolution digital SOC stock map compared with other available mapping products for the region. The data and high-resolution maps from this study can be used for future soil carbon assessment and monitoring.
Remote sensing for the earth sciences
- E Ben-Dor
- J R Irons
- G F Epema
- Reflectance
BEN-DOR, E.; IRONS, J. R.; EPEMA, G. F. Soil
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sciences. New York: J. Wiley & Sons, 1999.
Predição dos teores de carbono e nitrogênio do solo utilizando espectroscopia de infravermelho próximo. Planaltina: Embrapa Cerrados
- R L Marchao
- T Becquer
- D Brunet
MARCHAO, R.L.; BECQUER, T.; BRUNET, D. Predição
dos teores de carbono e nitrogênio do solo utilizando
espectroscopia de infravermelho próximo. Planaltina:
Embrapa Cerrados, 21 p. (Boletim de pesquisa e
desenvolvimento).2011