REMOTE SENSING FOR SCHEDULING IRRIGATION: REVIEW OF THERMAL INFRARED APPROACH

To answer the first question, plant temperature has been tested for a long time as an indicator of crop water status. Thanks to the recent progress of the thermal infrared technology, surface crop temperature can be detected both from airborne platforms and from hand-held instruments. A short review of several indices of crop water stress based on canopy temperature detected with thermal infrared sensors is presented here. Some critical considerations about one of the most popular ones, the CWSI, are reported also, together with tracks of new reexaminations.

In order to answer the second question we need also to know the amount of water used by crops, that is their evapotranspiration (ET). Some of the most recent methods to estimate ET using thermal infrared data are reviewed here: particular attention has been drawn to those requiring few standard information from ground meteorological stations.

Despite some limitations infrared thermometry appears to be a viable technique to schedule irrigation: timing of irrigations can be accomplished on the basis of crop water stress indices derived from canopy temperature (Tc) remotely detected in the thermal infrared waveband. Daily crop water requirements can be computed from the instantaneous midday values of Tc toghether with other meteorological obvervations.

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