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

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 different methodological approaches measuring 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, δ13C, 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, δ13C and stomatal conductance. Moreover, while canopy temperature measured with a thermal camera was better related to grain yield and δ13C 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.