Non-water-stressed baselines for irrigation scheduling with infrared thermometers: A new approach

Abstract

Surface temperature measured with infrared thermometers is an important tool for irrigation scheduling which has been in practice for some decades. Several indices have been developed to time irrigation events. The most useful is the Crop Water Stress Index (CWSI). Its use, however, relies on a non-water-stressed baseline that, although having a theoretical basis, is to be determined experimentally given the uncertainties related to the surface resistance of the crop. The drawbacks of this procedure, besides the non-transferability of the lines from place to place, are that the surface temperature measurements have always to be made under similar weather conditions. A new definition of a non-water-stressed baseline theoretically based and driven by weather variables that can easily be measured and/or estimated is proposed that allows measurements at any time of the day and whatever the weather conditions, thus simplifying the task of the irrigator.