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Dematte J.A.M.,University of Sao Paulo | Terra F.S.,University of Sao Paulo | Quartaroli C.F.,Embrapa Monitoramento por Satelite
Bragantia | Year: 2012

Remote sensing has a high potential for environmental evaluation. However, a necessity exists for a better understanding of the relations between the soil attributes and spectral data. The objective of this work was to analyze the spectral behavior of some soil profiles from the region of Piracicaba, São Paulo State, using a laboratory spectroradiometer (400 to 2500 nm). The relations between the reflected electromagnetic energy and the soil physical, chemical and mineralogical attributes were analyzed, verifying the spectral variations of soil samples in depth along the profiles with their classification and discrimination. Sandy soil reflected more, presenting a spectral curve with an ascendant form, opposite to clayey soils. The 1900 nm band discriminated soil with 2:1 mineralogy from the 1:1 and oxidic soils. It was possible to detect the presence of kaolinite, gibbsite, hematite and goethite in the soils through the descriptive aspects of curves, absorption features and reflectance intensity. A relation exists between the weathering stage and spectral data. The evaluation of the superficial and subsuperficial horizon samples allowed characterizing and discriminating the analytical variability of the profile, helping to soil distinguishing and classification.

Victoria D.D.C.,Embrapa Monitoramento por Satelite | da Paz A.R.,Federal University of Paraiba | Coutinho A.C.,Embrapa Informatica Agropecuaria | Kastens J.,Kansas Applied Remote Sensing | Brown J.C.,University of Kansas
Pesquisa Agropecuaria Brasileira | Year: 2012

The objective of this work was to evaluate a simple, semi-automated methodology for mapping cropland areas in the state of Mato Grosso, Brazil. A Fourier transform was applied over a time series of vegetation index products from the moderate resolution imaging spectroradiometer (Modis) sensor. This procedure allows for the evaluation of the amplitude of the periodic changes in vegetation response through time and the identification of areas with strong seasonal variation related to crop production. Annual cropland masks from 2006 to 2009 were generated and municipal cropland areas were estimated through remote sensing. We observed good agreement with official statistics on planted area, especially for municipalities with more than 10% of cropland cover (R2 = 0.89), but poor agreement in municipalities with less than 5% crop cover (R2 = 0.41). The assessed methodology can be used for annual cropland mapping over large production areas in Brazil.

Costa V.L.,IAC | de Maria I.C.,IAC | Camargo O.A.,IAC | Grego C.R.,Embrapa Monitoramento por Satelite | Melo L.C.A.,Federal University of Vicosa
Revista Brasileira de Engenharia Agricola e Ambiental | Year: 2014

In agricultural soils receiving sewage sludge and subjected to water erosion, may occur intense transport of phosphorus (P) to the lower parts of the landscape and eventually to water bodies. The objective of this study was to evaluate the spatial distribution of P in an Oxisol cultivated with maize. The treatments were evaluated with application of mineral fertilization (MF) and sewage sludge (SS). Soil samples were collected following a sampling grid of 69 points in each treatment at the beginning and at the end of the crop cycle, in an experimental area with 10% slope. There was a moderate spatial dependence of P in the soil in the treatment of MF, resulting in higher concentrations of P in the deeper layers of the soil caused by erosion. The same standard was observed for the soil attributes sum of bases, cation exchange capacity and soil organic matter. Conversely, when SS was applied there was a randomized distribution of P in the plots because of the non-uniform manner of its application. Such random distribution of P showed correlation with soil organic matter.

Brown J.C.,University of Kansas | Kastens J.H.,University of Kansas | Coutinho A.C.,Embrapa Informatica Agropecuaria | Victoria D.D.C.,Embrapa Monitoramento por Satelite | Bishop C.R.,University of Kansas
Remote Sensing of Environment | Year: 2013

MODIS 250-m NDVI and EVI datasets are now regularly used to classify regional-scale agricultural land-use practices in many different regions of the globe, especially in the state of Mato Grosso, Brazil, where rapid land-use change due to agricultural development has attracted considerable interest from researchers and policy makers. Variation exists in which MODIS datasets are used, how they are processed for analysis, and what ground reference data are used. Moreover, various land-use/land-cover classes are ultimately resolved, and as yet, crop-specific classifications (e.g. soy-corn vs. soy-cotton double crop) have not been reported in the literature, favoring instead generalized classes such as single vs. double crop. The objective of this study is to present a rigorous multiyear evaluation of the applicability of time-series MODIS 250-m VI data for crop classification in Mato Grosso, Brazil. This study shows progress toward more refined crop-specific classification, but some grouping of crop classes remains necessary. It employs a farm field polygon-based ground reference dataset that is unprecedented in spatial and temporal coverage for the state, consisting of 2003 annual field site samples representing 415 unique field sites and five crop years (2005-2009). This allows for creation of a dataset containing "best-case" or "pure" pixels, which we used to test class separability in a multiyear cross validation framework applied to boosted decision tree classifiers trained on MODIS data subjected to different pre-processing treatments. Reflecting the agricultural landscape of Mato Grosso as a whole, cropping practices represented in the ground reference dataset largely involved soybeans, and soy-based classes (primarily double crop 'soy-commercial' and single crop 'soy-cover') dominated the analysis along with cotton and pasture. With respect to the MODIS data treatments, the best results were obtained using date-of-acquisition interpolation of the 16-day composite VI time series and outlier point screening, for which five-year out-of-sample accuracies were consistently near or above 80% and Kappa values were above 0.60. It is evident that while much additional research is required to fully and reliably differentiate more specific crop classes, particular groupings of cropping strategies are separable and useful for a number of applications, including studies of agricultural intensification and extensification in this region of the world. © 2012.

The aim of this study was to evaluate the spatial variability of some soil physical attributes and its effects on the development of rubber trees cultivated with leguminous cover crops. The experiment was conducted at Pólo Regional de Desenvolvimento Tecnológico dos Agronegócios do Centro Norte, located in Pindorama, SP, Brazil, on a Typic Kandiudalf. Saturated infiltration rate was evaluated at 0.10 and 0.20cm depth while macro and micro porosity and bulk density were evaluated at 0-0.10, 0.10-0.20, 0.20-0.40 and 0.40-0.60 m layer. Rubber tree plant development was evaluated for four years (1996-1999) through plant stem perimeters and its increase with time. Descriptive statistics was used to calculate and analyze the dispersion and central limit parameters. Geostatistics was used to evaluate the spatial dependence through semivariograms, to perform interpolation using kriging and to construct contour maps for georeferenced data. Spatial dependence was found for all soil physical properties with the range of spatial dependence varying between 15 and 90m. Saturated infiltration rate showed spatial dependence with no relation with plant development evaluations or with any other soil physical attributes. High values for bulk density and micro porosity at 0.20-0.40 m indicate soil compaction at this layer. The plant stem perimeter increased linearly with time while the rate of increase in perimeter decreased with time. The mean increase in plant perimeter was smaller for the winter as compared with the summer measurements. The spatial distribution for rubber tree growth as a function of time presented high continuity as measured by the low nugget effect values and it showed close relation with bulk density values, as the regions with low bulk density showed large values for rubber tree stem perimeter.

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