Resposta espectral do feijoeiro a diferentes doses de nitrogênio

• Autor(a) principal: Campos, Diogo Santos
• Data de Publicação: 2009
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/654
• topic: Feijão; Análise espectral; Sensoriamento remoto; Agricultura de precisão; Common beans; Spectral analysis; Remote sensing; Precision agriculture; CNPQ::CIENCIAS AGRARIAS::ENGENHARIA AGRICOLA::MAQUINAS E IMPLEMENTOS AGRICOLAS

The search for sustainable agriculture, with production of food at competitive cost and less impact to the environment, has led many producers to adopt techniques related to precision agriculture. The use of methods that provides rapid diagnosis of the nutritional status of plants is a need for a recommendation for optimal fertilization. The main objective of this work was to evaluate, under field conditions, the spectral response of bean canopy subjected to different nitrogen rates. Two experiments were conducted where data were obtained from the randomized block design with three replicates, distributed in a factorial 5 x 6. The treatments consisted of five nitrogen (N) rates applied at planting and six N rates applied as sidedress using urea-based fertilizers. For each experiment, there were seven measurements using a spectrometer. Parallel to the radiometric data, in each parcel readings were made using a portable chlorophyll meter (SPAD). For the same leaves used for the determination of SPAD values, the levels of leaf nitrogen were determined. The yield and yield components of number of pods per plant, number of grains per pod and one hundred grain mass were determined. From the radiometric data were calculated average values of reflectance and generated vegetation indices. The experiments were divided into two stages, before and after sidedressing nitrogen. Before the sidedressing for each date, the regression analysis was made between the N rates applied at planting and the SPAD values, leaf nitrogen and vegetation indices. To visualize the spectral reflectance of the bean canopy, average spectral response graphics were generated for each N rates applied. The quantity of relationship between variables leaf nitrogen, SPAD values and average values of vegetation indices was evaluated by correlation analysis. After sidedressing, the existence of a functional relationship between of N rates applied before and after sidedressing and the SPAD values, leaf nitrogen, vegetation indices, yield beans and your components, were made by regression analysis. The evaluation of the relationship between the group of vegetation indices and yield beans and your components was made by canonical correlation analysis. Studies conducted before sidedressing have concluded that the use of SPAD values and leaf nitrogen may be used to evaluate the rates of nitrogen fertilizer if the soil is of low natural fertility. Variations in the amount of biomass of the canopy changed the spectral response of the bean. The vegetation indices WDRVI and SAVI were more efficient in identifying the functional relationship between N rates applied at planting and the average vegetation indices, when compared with the index NDVI. The vegetation indices studied showed no significant correlation with the values of leaf nitrogen. Only for the soil is of low natural fertility, after sidedressing the use of SPAD values, leaf nitrogen and vegetation indices could discriminate N rates applied at planting and sidedressing. For that soil, the N rates applied at planting and sidedressing increased significantly the yield, the number of pods per plant and the number of grains per pod. Through analysis of canonical correlation was identified that for the soil is of high fertility, the groups the average values vegetation indices and the group bean yield components were independent. For the soil is of low natural fertility, the groups considered were not independent.