Parametrização de modelo para estimação da produtividade de soja nas regiões do Planalto Médio, das Missões e do Alto Vale do Uruguai, Rio Grande do Sul / Parameterization of a model to estimate the soybean yield in the Planalto Médio, Missões and Alto Vale do Uruguai regions, State of Rio Grande do Sul, Brazil

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The soybean has a highlight position in Brazilian and world wide agricultural scenario. Amongst the States of bigger agricultural tradition in Brazil, the State of Rio Grande do Sul is one of the greatest producers and exporters of grains, being responsible for approximately 20% of the national production of soybean, with an average productivity of 2.667kg.ha-1 (IBGE, 2005). Due to great importance of the agricultural activities in the national economy, a rigorous control of the agricultural production is necessary, as much for the establishment of politics of prices how much for the maintenance of the regulating supplies of the government. So that the control mechanisms work with the expected efficiency, they are necessaries actualized, precise and accurate information about the volume of agricultural production. The objective of this study was to carry on the parameterization of the agrometeorological-spectral model to estimate the soybean yield for small areas in the regions of Planalto Médio, Missões and Alto Vale do Uruguai, in the State of Rio Grande do Sul. This parameterization of the model for small areas intends to minimize the errors of super estimate and sub estimate of the soybean yield. Data from 10 meteorological stations located into the study region and around it, beyond of satellite images of Normalized Difference Vegetation Index in the period from 1982 to 2000 was used. Data, from official statistics of IBGE (Brazilian Institute of Geography and Statistics), of soybean yield in the same period was collected. The parameterization was realized for 696 areas, each one with 81km² (9x9km), and considering seven different values of Capacity of Available Water (CAD) of ground. The calculations that had generated the parameters had been carried through in Visual Basic programming. Through the calculated parameters the values of estimated productivity for the period of adjustment of the model had been gotten. The estimated values had been compared with the values considered as observed, with the purpose to evaluate the efficiency of the model and the validity of the parameters in the different areas. The values of estimated yield by the application of the parameterized model in each area had shown good adjustment with the observed values (official statistics). The parameterization of the agrometeorological-spectral model for smaller areas inside the study region became unnecessary the factor of correction, used by Melo; Fontana; Berlato (2003), to obtain the yield estimative. The introduction in the model of a spectral term, deriving from images of Normalized Difference Vegetation Index, tends to promote yield estimated values closer the observed values, in comparison to the yield estimated values obtained through the application of the multiplicative model of Jensen (1968), modified by Berlato (1987), that considers just the water availability. This model can directly be incorporated in harvests forecasting programs or be used directly by the producers and entities with relations to the agricultural activity.

ASSUNTO(S)

soja yiel produtividade rio grande do sul soybean rio grande do sul

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