ASABE Technical Library - Abstract

Abstract.

This study aims to evaluate the relationship between the spectral behavior of the soybean canopy, the the leaf area index (LAI), and the production of biomass. The research was conducted in area planted with irrigated soybean in “Busato I” farm, São Desidério, Bahia, Brasil. Four samples of plants were taken in the area (09/29/2013, 12/06/2013, 01/17/2014 and 02/07/2014), being the aerial biomass of plants separated into stem, leaves, flowers and pods for obtaining the dry matter. For each date on study was used the MOD09GQ product available on the NASA Web site (www.reverb.echo.nasa.gov). It were calculated for each image from the use of Model Maker tool of the ERDAS 9.1 software considering the scale factor and the transformed reflectance, values of the normalized difference vegetation index (NDVI) and the Index Vegetation Soil Adjusted (IVSA). With the IV’s values, it was estimated the soybean´s LAI testing three methods: a) Method LAI1, suggested by RIZZI and RUDORFF (2007); b) Method LAI2, with the equation adjusted by Xavier and Vetorazzi (2004); and c) Method LAI3, was obtained on the basis of the model of ALLEN et al. , (2002). The results of the LAI´s were used for the estimation of aerial biomass production, according to the model of Montheith, which considers the accumulation of absorbed photosynthetic active radiation (PAR). The IV’s derived from the MODIS images proved to be effective for obtaining the LAI by the LAI3 method and can be useful in monitoring the evolution of the soybean crop in the field, because this model that considers the PARradiation and LAI estimated from the spectral vegetation index, showed a good correlation with the field data in the determination of the soybean biomass.