Temporal variation of normalized difference vegetation index (NDVI) and calculation of the crop coefficient (K_c ) from NDVI in areas cultivated with irrigated soybean

Variação temporal do Índice de Vegetação por Diferença Normalizada (NDVI) e obtenção do coeficiente de cultura (K_c ) a partir do NDVI em áreas cultivadas com soja irrigada

ABSTRACT:

Vegetation indices obtained by remote sensing products have various applications in agriculture. An important application of the Normalized Difference Vegetation Index (NDVI) is obtaining the crop coefficient (K_c). The aims of this study were to analyze NDVI temporal profiles and to obtain K_c from the NDVI vegetation index product MOD13Q1. The analysis is based on the phenological stages of irrigated soybean crops in the municipality of Planura/MG during the 2010/2011 growing season. Areas planted with irrigated soybean were identified through fieldwork. Temporal series of the MOD13Q1 products were used to analyze NDVI, allowing the extraction of NDVI values for all points in the period studied. The NDVI temporal profiles showed a similar pattern to each other and corresponded to the crop cycle. The K_cNDVI values for the MOD13Q1 products were well correlated to the FAO K_c values (r²=0.72). Thus, NDVI can be used as an alternative for obtaining crop coefficient (K_c).

Key words:
MOD13Q1; phenological stages; temporal profiles