Comparative performance of remote sensing methods in assessing wheat performance under Mediterranean conditions

Abstract

Vegetation indices and canopy temperature are the most usual remote-sensing approaches to assess
cereal performance under Mediterranean conditions. However wide differences exist in the costs of the
different equipment deployed to measure vegetation indices (e.g. spectroradiometers versus conventional
red/green/blue cameras) or canopy temperature (infrared thermometers versus thermal cameras).
In this study we compared differentmethodological approachesmeasuring vegetation indices and canopy
temperature in durum wheat (Triticum turgidum L. ssp. durum (Desf.) Husn.) and bread wheat (Triticum
aestivum L.) under different water conditions. These two categories of indices were correlated against
grain yield during two consecutive years and with total biomass as well as water status (evaluated as carbon
isotope composition, ı13C, and stomatal conductance) and nitrogen status (nitrogen and chlorophyll
content) of the flag leaf during the first year. For the two crop species, and regardless of the device used,
vegetation indices (the green area and the greener area) obtained with conventional cameras and the
normalized difference vegetation index (NDVI) measured with a spectroradiometer were significantly
correlated with grain yield, 13C and stomatal conductance. Moreover, while canopy temperature measured
with a thermal camera was better related to grain yield and 13C than when measured with a low
cost device such as an infrared thermometer, the latter approach still performs reasonably well when
assessing yield and water status. This study highlights the usefulness of low-cost approaches to assess
crop growth and water status in wheat under Mediterranean conditions