Potato yield and quality are highly dependent on an adequate supply of water. In this study, 3 years of information from thermal and RGB images were collected to evaluate water status in potato fields. Irrigation experiments were conducted in commercial potato fields (Desiree; drippers). Two water-deficit scenarios were tested: a short-term water deficit (by suppressing irrigation for a number of days before image acquisition), and a long-term cumulative water deficit. Ground and aerial images were acquired in various phenological stages along the potato growing season. Effects of irrigation treatments were recorded by thermal indices and biophysical measurements of stomatal conductance (SC), leaf water potential, leaf osmotic potential and gravimetric water potential in soil. Canopy temperature was delineated from the thermal images with and without fused information from the RGB image. Crop water stress index (CWSI) was calculated, using three forms of minimum baseline temperature: empirical, theoretical and statistical. An empirical evaluation of maximum baseline temperature of Tair + 7 °C was used in all CWSI forms examined. Statistical tests and comparison of CWSI with biophysical measurements were performed to evaluate the responses to irrigation treatments. The results indicated a high correlation of CWSI with SC from tuber initiation to maturity based on ground and aerial data (0.64 ≤ R2 ≤ 0.99). Similar trends of increasing CWSI from well to deficit-irrigated treatments were found in all three growing seasons. The results also showed that CWSI may be calculated based merely on thermal imagery data.
Bibliographical noteFunding Information:
Acknowledgements Financial support for this project was provided by the Binational Agricultural Research and Development Fund (through Research Grant Award No. IL-4255-09). Aerial images were acquired by Icaros Geosystems Ltd. (Herzliya Pituach, Israel). The authors wish to express their appreciation for the vital contributions of Gadi Hadar and Ronen Pe’er-Cohen, potato growers from Kibbutz Ruhama who managed the irrigation in this study. Moreover, the field experiments could not have been performed without the collaboration of Yossi Sofer of Haifa Chemicals, Ltd.
- Remote sensing
- Water stress