Assessing the relationship between shire winter crop yield and multi-temporal MODIS NDVI and EVI images

Abstract

Australian researchers have been developing robust yield simulation models, based mainly on the crop growth response to the rainfall amount and distribution during the crop season. However, better knowledge of spatial distribution of yields in the production regions can be estimated by the use of remote sensing techniques. The objective of this study was to analyse the relationship between winter crop yields and the spectral information available at MODIS vegetation index images at the shire level. The study was carried out in the Jondaryan and Pittsworth shires, Queensland, Australia. Five years (2000 to 2004) of 250m, 16-day composite of MODIS NDVI and EVI images were used during the winter crop season (April to November). For these shires, a mask of cropping area was applied by using a land use classification map derived from Landsat TM. Multi-temporal profiles of the NDVI and the EVI imagery for each crop season were displayed and analysed. Wheat and barley yields, provided by the Australian Bureau of Statistics, were correlated to the maximum and to the integrated crop season values for both NDVI and EVI at the shire level. The temporal VI profiles were quite similar in Jondaryan and Pittsworth, with minimum values in April, May and June, a peak in August, and decreasing until November. Bigger differences were found between years. The correlation analysis between the winter crop yields and VIs pointed out that EVI images were better than the NDVI ones. Most part of the coefficients was statistically significant when using EVI spectral information from the Integrated and Maximum results. The results presented in this paper showed that the VI images are a powerful tool to assess near real-time biomass status.