Erosion Study In The Ceveiro Watershed (piracicaba, Sp). Ii - Interpreting Soil Loss Tolerance Using The Soil Useful Life Index Methodology [estudo Da Erosão Na Microbacia Do Ceveiro (piracicaba, Sp). Ii - Interpretação Da Tolerância De Perda De Solo Utilizando O Método Do índice De Tempo De Vida]

Accelerated soil erosion, a process basically induced by human activities contributes greatly to the degradation of arable land quality throughout the world, and is the main nonpoint source of surface water resource pollution. Considering the effective demand for developing indicators to evaluate the impact of soil erosion on soil quality in agriculture production systems, the objective of this study was to develop an index with a predictive value to be applied as a planning tool for interpreting soil loss tolerance in agricultural areas. The "Soil Useful Life Index" was developed and applied to diagnose erosion in an area predominantly used for sugarcane cultivation in the Piracicaba county, São Paulo State, Brazil. Geotechnology and geostatistics analysis methods were used in this study and the data processed and analyzed in a geographic matrix information system. Average annual soil loss rates had been estimated in a previous study using the universal soil loss equation (USLE), adjusting the model factors to the local study conditions. A 0.2 mm year-1 renewal rate was assumed in the soil useful life index calculation, and two depths considered minimal for agricultural purposes (50 and 100 cm) were analyzed. The evaluation of soil thickness revealed that shallower soils are predominant in the study area, with average depths of 78 cm in areas occupied by sugarcane and 72 cm in areas used for other purposes. The application of the soil useful life index revealed that at the critical depth of 50 cm, the useful life of soils occupied by sugarcane is 178 years. By maintaining the curren t soil loss expectations, little more than 70 years will be sufficient to degrade 50% of the area cultivated with sugarcane (soil half-life). The situation worsens at critical depths of 100 cm. Average soil useful life in areas occupied by sugarcane falls to only 102 years, and soil half-life is only 42 years. The method also permitted an estimation of the proportions of areas with sugarcane where the impact is already permanent (zero soil useful life) at 19 and 74%, that is, where soil loss rates exceed the soil renewal rate, and soil thickness is already less than the critical depths considered, 50 and 100 cm, respectively. Furthermore, under the current use and management conditions, the resources conservation, that is the soil renewal rate is higher than the estimated soil loss rates by erosion, can be characterized in only 7.6 ha, or less than 1% of the area under sugarcane. Therefore, in more than 99% of the area occupied by sugarcane the estimated rates of soil loss by erosion exceed the soil renewal rate (p > r), characterizing a situation of resource degradation. 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Aplicação da análise harmônica por séries de Fourier para a previsão de produtividade da cultura do café no Estado de Minas Gerais Forecast of coffee crop productivity by harmonic analysis, using the Fourier series in Minas Gerais State, Brazil

O objetivo deste trabalho foi obter um modelo de previsão de produtividade para a cultura do café, em sete municípios do Estado de Minas Gerais. Submeteram-se à análise harmônica por séries de Fourier, séries de produtividades representativas de cada município, das quais se extraíram os coeficientes até o sétimo harmônico, submetendo-os à regressão linear múltipla nos três primeiros componentes principais de um conjunto de 33 variáveis inerentes à produção cafeeira. Essas variáveis foram médias de 15 anos correspondentes aos mesmos anos das produtividades e subdivididos em quatro períodos trimestrais, ao longo do ciclo produtivo da cultura (julho a junho). O modelo mostrou-se inconsistente, apresentando erros das estimativas bastante discrepantes, evidenciando a complexidade de modelagem de previsão de safras para a cultura do café.<br>The objective of this work was to obtain a forecast model of coffee crop productivity in seven municipal districts of Minas Gerais State, Brazil. The harmonic analysis in Fourier series was applied on productivity series to each location. The obtained coefficients until the harmonic seventh were submitted to multiple linear regression in the first three principal components of a group of 33 inherent variables of coffee production. These variables were averages of 15 years corresponding to the same years of productivity and subdivided in four quarterly periods during the agricultural year (July to June). The model did not prove adequate, since the results presented errors of estimatives with great discrepancies evidencing the complexity of yield forecast of coffee crop

Estimativa da produtividade de café com base em um modelo agrometeorológico-espectral

O objetivo deste trabalho foi avaliar um modelo agrometeorológico-espectral, para estimar a produtividade de cafezais. Utilizaram-se imagens do sensor MODIS e dados agrometeorológicos do modelo regional de previsão do tempo (ETA), para fornecer as variáveis de entrada para o modelo agrometeorológico-espectral da mesorregião geográfica sul/sudoeste do estado de Minas Gerais nos anos-agrícolas de 2003/2004 a 2007/2008. A variável espectral de entrada do modelo agrometeorológico-espectral, índice de área foliar (IAF), usada no cálculo da produtividade máxima, foi estimada com o índice de vegetação por diferença normalizada (NDVI), obtido de imagens MODIS. Outras variáveis de entrada no modelo foram: dados meteorológicos gerados pelo modelo ETA e a capacidade de água disponível no solo. Ao comparar a produtividade média estimada pelo modelo com a fornecida oficialmente pelo IBGE, as diferenças relativas obtidas em escala regional foram de: 0,4, 3,0, 5,3, 1,5 e 8,5% para os anos agrícolas 2003/2004, 2004/2005, 2005/2006, 2006/2007 e 2007/2008, respectivamente. O modelo agrometeorólogico-espectral, que tem como base o modelo de Doorenbos & Kassan, foi tão eficaz para estimar a produtividade dos cafezais quanto o modelo oficial do IBGE. Além disso, foi possível espacializar a quebra de produtividade e prever 80% da produtividade final na primeira quinzena de fevereiro, antes do início da colheit