Marcos Rafael Nanni

Optimum size in grid soil sampling for variable rate application in site-specific management

The importance of understanding spatial variability of soils is connected to crop management planning. This understanding makes it possible to treat soil not as a uniform, but a variable entity, and it enables site-specific management to increase production efficiency, which is the target of precision agriculture. Questions remain as the optimum soil sampling interval needed to make site-specific fertilizer recommendations in Brazil. The objectives of this study were: i) to evaluate the spatial variability of the main attributes that influence fertilization recommendations, using georeferenced soil samples arranged in grid patterns of different resolutions; ii) to compare the spatial maps generated with those obtained with the standard sampling of 1 sample ha -1 , in order to verify the appropriateness of the spatial resolution. The attributes evaluated were phosphorus (P), potassium (K), organic matter (OM), base saturation (V%) and clay. Soil samples were collected in a 100 × 100 m georeferenced grid. Thinning was performed in order to create a grid with one sample every 2.07, 2.88, 3.75 and 7.20 ha. Geostatistical techniques, such as semivariogram and interpolation using kriging, were used to analyze the attributes at the different grid resolutions. This analysis was performed with the Vesper software package. The maps created by this method were compared using the kappa statistics. Additionally, correlation graphs were drawn by plotting the observed values against the estimated values using cross-validation. P, K and V%, a finer sampling resolution than the one using 1 sample ha -1 is required, while for OM and clay coarser resolutions of one sample every two and three hectares, respectively, may be acceptable.

REMOTE SENSING IN THE RECOGNITION AND MAPPING OF TROPICAL SOILS DEVELOPED ON TOPOGRAPHIC SEQUENCES

The authors compare information on soil maps of the São Paulo region, Brazil (obtained by four different methodologies) with ground truth data and a preexisting semi-detailed soil map. The methodologies for compiling the new soil maps included: (1) conventional (field) cartographic methods; (2) air photo interpretation; (3) automated processing of radiometric data; and (4) use of radiometric data in conjunction with air photo analysis and planimetric/altimetric observations. The remote sensing methodologies produced soil maps similar to the detailed map (1) and substantially better than the pre-existing semi-detailed one. The utility of these techniques to soil surveys at rather large scales, and for tropical soil mapping in general, is assessed.

Comportamento da linha do solo obtida por espectrorradiometria laboratorial para diferentes classes de solo

Com vistas em avaliar o comportamento da linha do solo para diferentes classes de solos, este trabalho foi realizado, utilizando-se dados de reflectância por meio de um espectrorradiometro em laboratorio. Amostras representativas dos horizontes superficiais e subsuperficiais de 18 classes coletadas em uma area piloto no Municipio de Rafard, sudoeste de Sao Paulo, foram secas, peneiradas e acondicionadas para leitura espectral. Os dados foram tabulados, para simularem as bandas 3 e 4 do TM-Landsat e construcao dos graficos. Os resultados demonstraram que as linhas de solo obtidas para as amostras de ambas as camadas comportaram-se de maneira semelhante, estando dispostas ortogonalmente aos eixos de um grafico, com valores de R2 proximos a 1,0 para todas as classes avaliadas. Nao se observou uma unica linha de solo, embora os dados revelem que cada solo apresenta uma linha individual e caracteristica. De modo complementar, destacou-se a utilizacao deste indice como metodo auxiliar na discriminacao de classes de solos, uma vez que os solos com textura arenosa e com menores teores de Fe total discriminaram-se daqueles mais argilosos e com maiores teores de Fe, alem de apresentarem valores de reflectância mais elevados. Por fim, constatou-se que a materia orgânica nao constituiu fator determinante no comportamento espectral em relacao a linha do solo.

Análise discriminante dos solos por meio da resposta espectral no nível terrestre

The objective of this study was to develop and test a discrimination method for soil classes by their spectral response (SR), using a laboratory sensor. Spectral data were used to develop statistical model for discriminating soil classes in an area at the southwest of Sao Paulo State, Brazil. Discriminant equations were developed for 18 soil classes. The spectral data were obtained in superficial and subsuperficial soil samples in the study area, with a total of 370 samples. The samples were collected in 185 ha, with one borehole per ha. The results showed that soil classes can be separated and delimitated by discriminant analysis. The analysis presented a classification index higher than 80% for each soil class. The global classification index was 90.71%, when all soil classes were used to develop the model, and 93.44% when most individuals classes were used. The simulated statistical test was efficient in the discriminant analysis, presenting a classification index higher than 91%, with a global error of 8.8%. The analysis demonstrated a reduction of the model quality when applied for 20% sub-group of the samples with global error of 33.9%. The method helped in the soil classes discrimination by their spectral reflectance, based on their physical interaction with electromagnetic energy.

Soil chemical alterations promoted by fertilizer application assessed by spectral reflectance

Precision agriculture technologies are pointing to the necessity of using sensors to collect soil information to assist in fertilizer dose evaluation. This study evaluates the effect of increasing doses of lime, thermophosphate, and organic matter on spectral reflectance of a tropical soil. We analyzed the most common tropical soil in Brazil, a medium texture Typic Haplortox occurring in the state of São Paulo, Brazil. Physical chemical and mineralogical analyses were carried out both before and after treatments. A spectroradiometer with a 450–2500-nm spectral range was used in the laboratory to capture spectral data. The application of increasing doses of lime increased the reflectance intensity as a result of the presence of calcium. The application of thermophosphate altered reflectance intensity primarily because of the presence of phosphorous. Organic matter reduced the reflectance when compared with the control. Chemical variations promoted by fertilizer application altered the intensity of reflected energy mainly between 826 and 2500 nm. However, there were no significant changes in soil absorption features except when applied to the organic product. The high values of determination coefficients for calcium and organic matter indicate that they can be estimated through soil-reflected energy, and, consequently, will be useful in precision farming systems.

Diferenciação espectral de solos utilizando dados obtidos em laboratório e por sensor orbital

A huge amount of soil samples would be necessary to determine with precision the limits of soil units. Techniques that would help on soil surveys such as the remote sensing ones have been proved to be of great value. The objective of this work was to evaluate the possibility of differentiating soils using spectral data from laboratory and satellite sensors. A study area with soils originated from two different parent materials, sandstone with loamy cement and basalt, was selected. A grid (100 m x 100 m) was used, totalizing 473 sampling points in the depths 0-20 cm (superficial, A) and 80-100 cm (subsuperficial, B). A soil map of the area with 28 mapping units was generated. The laboratory spectra (450 to 2500 nm) were obtained with an IRIS spectroradiometer. The orbital reflectance was obtained by image processing and overlaying of the TM-Landsat-5 bands in the sampling points. Discriminant equations were generated by statistical treatment with the SAS software. From the seventy initial variables from laboratory data, fifty six were selected to generate the models of the equations; for orbital data, six of the seven TM bands were selected. The equations were tested and the confusion matrix were obtained. Discriminant equations from laboratory data presented 81% success and the equations with orbital data 40%, however, for the satellite data it was verified a good efficiency for separating soils from different parent materials.

Investigação sorológica de casos subclínicos de leishmaniose tegumentar após um surto em uma localidade endêmica

Subclinical cases of cutaneous leishmaniasis were investigated in a district of Maringá, State of Paraná, by means of the indirect immunofluorescence reaction and enzyme immunoassay. Among the 130 samples analyzed, one presented titer 40 and three presented titer 20 in the indirect immunofluorescence reaction, while 11 samples were positive in the enzyme immunoassay reaction. These data suggest that subclinical cases exist at this locality.

Remote Sensing from Ground to Space Platforms Associated with Terrain Attributes as a Hybrid Strategy on the Development of a Pedological Map

There is a consensus about the necessity to achieve a quick soil spatial information with few human resources. Remote/proximal sensing and pedotransference are methods that can be integrated into this approach. On the other hand, there is still a lack of strategies indicating on how to put this in practice, especially in the tropics. Thus, the objective of this work was to suggest a strategy for the spatial prediction of soil classes by using soil spectroscopy from ground laboratory spectra to space images platform, as associated with terrain attributes and spectral libraries. The study area is located in Sao Paulo State, Brazil, which was covered by a regular grid (one per ha), with 473 boreholes collected at top and undersurface. All soil samples were analyzed in laboratory (granulometry and chemical), and scanned with a VIS-NIR-SWIR (400–2500 nm) spectroradiometer. We developed two traditional pedological maps with different detail levels for comparison: TFS-1 regarding orders and subgroups; and TFS-2 with additional information such as color, iron and fertility. Afterwards, we performed a digital soil map, generated by models, which used the following information: (i) predicted soil attributes from undersurface layer (diagnostic horizon), obtained by using a local spectral library; (ii) spectral reflectance of a bare soil surface obtained by Landsat image; and (iii) derivative of terrain attributes. Thus, the digital map was generated by a combination of three variables: remote sensing (Landsat data), proximal sensing (laboratory spectroscopy) and relief. Landsat image with bare soil was used as a first observation of surface. This strategy assisted on the location of topossequences to achieve soil variation in the area. Afterwards, spectral undersurface information from these locations was used to modelize soil attributes quantification (156 samples). The model was used to quantify samples in the entire area by spectra (other 317 samples). Since the surface was bare soil, it was sampled by image spectroscopy. Indeed, topsoil spectral laboratory information presented great similarity with satellite spectra. We observed angle variation on spectra from clayey to sandy soils as differentiated by intensity. Soil lines between bands 3/4 and 5/7 were helpful on the link between laboratory and satellite data. The spectral models of soil attributes (i.e., clay, sand, and iron) presented a high predictive performance (R2 0.71 to 0.90) with low error. The spatial prediction of these attributes also presented a high performance (validations with R2 > 0.78). The models increased spatial resolution of soil weathering information using a known spectral library. Elevation (altitude) improved mapping due to correlation with soil attributes (i.e., clay, iron and chemistry). We observed a close relationship between soil weathering index map and laboratory spectra + image spectra + relief parameters. The color composite of the 5R, 4G and 3B had great performance on the detection of soils along topossequences, since colors went from dark blue to light purple, and were related with soil texture and mineralogy of the region. The comparison between the traditional and digital soil maps showed a global accuracy of 69% for the TFS-1 map and 62% in the TFS-2, with kappa indices of 0.52 and 0.45, respectively. We randomly validated both digital and traditional maps with individual plots at field. We achieve a 75% and 80% agreement for digital and traditional maps, respectively, which allows us to conclude that traditional map is not necessarily the truth and digital is very close. The key of the strategy was to use bare soil image as a first step on the indication of soil variation in the area, indicating in-situ location for sample collection in all depths. The current strategy is innovative since we linked sensors from ground to space in addition with relief parameters and spectral libraries. The strategy indicates a more accurate map with less soil samples and lower cost.

In situ separation of soil types along transects employing Vis-NIR sensors: a new view of soil evaluation

Soil components, such as organic matter, the levels and form of iron oxides, moisture and texture, influence the interaction of the soil with electromagnetic energy, so that knowledge of the energy reflected by different classes of soil is therefore of help in their discrimination. The aim of this study was to evaluate the possibility of differentiating classes of soils along two transects, by means of the field spectral behaviour of different classes, using both visual and multivariate statistical analysis. Equidistant points were marked along the transects, 100 m apart, where geo-referenced soil samples were collected from the surface layer at a depth of 0 to 0.20 m. In the area under study, ten classes of soil were described by means of laboratory analysis of surface samples and a morphological description of the profiles, with each soil being classified according to the Brazilian System of Soil Classification. For separating soil units and establishing their boundaries in the landscape three methods were used: a) traditional, evaluating the correlation between soil and landscape; b) qualitative assessment of the spectral curves; c) multivariate analysis for discrimination of the classes of soil. Comparison of these methods made possible the use of spectroradiometry in differentiating the classes of soil, with the statistical method separating a larger number of classes. It was possible to delimit the boundaries of the soil units in the area under study, as well as differences in texture, colour, total iron and organic matter between units, by varying the spectral responses of the soil samples being tested.

Infiltração de água no solo em um latossolo vermelho da região sudoeste dos cerrados com diferentes sistemas de uso e manejo

Na regiao do Cerrado, as atividades agricolas tem provocado impactos negativos, principalmente, na qualidade do solo e da agua. Tanto em sistemas de exploracao agricola ou de pecuaria, com diferentes manejos, a degradacao fisica do solo e uma das consequencias da reducao da produtividade. O objetivo deste trabalho foi verificar a infiltracao de agua no solo sob influencia de diferentes sistemas de manejo em um Latossolo Vermelho distrofico na regiao dos Cerrados. Os tratamentos foram os seguintes sistemas de manejo: a) solo sob vegetacao nativa; b) solo com implantacao de lavoura de soja durante um ano, seguido de tres anos de pastagens; c) solo com implantacao de lavoura de soja durante quatro anos, seguidos por quatro anos de pastagem; d) solo com lavoura de soja continua em sistema de plantio direto; e e) solo com pastagem continuamente. Foram avaliadas, no periodo de 1995 a 2002, a velocidade de infiltracao basica (VIB) e a infiltracao de agua acumulada no solo, utilizando o metodo de duplos aneis concentricos. Os usos do solo com sistema de lavoura continua, pecuaria continua e integracao lavoura-pecuaria tiveram a velocidade de infiltracao basica e infiltracao acumulada reduzidas em relacao ao solo com vegetacao nativa na regiao do Cerrado. Entre os sistemas estudados, o sistema de integracao lavoura-pecuaria foi o que apresentou valores mais proximos aos do solo sob vegetacao nativa.