Comparing canopy temperature and leaf water potential as irrigation scheduling criteria of potato in water-saving irrigation strategies

Abstract

Irrigation scheduling is important in irrigation water management. In this study, full (FI),deficit (DI) and partial root drying (PRD) irrigation strategies were applied in Agria and Ramospotato cultivars. Canopy temperature (CT) and leaf water potential (LWP) were assessed as thepotential tools for irrigation scheduling during the vegetative and productive growth stages.LWP varied between ca. -1.4 and -1.6 MPa and was not significantly different between FI, DIand PRD irrigation treatments. The LWP and CT values were not significant between the twopotato cultivars during the measurements, but CT was frequently significant between theirrigation treatments such that the PRD treatments were significantly 5 and 2 oC warmer than FIand DI treatments, respectively. Higher CT in PRD caused significant yield penalty such that DIand FI produced almost two times higher fresh tuber yield. Analysis revealed that CT hadsignificantly higher correlation (r=0.66) with water productivity (weight of fresh tuber yielddivided by volume of applied irrigation water) than LWP, which its correlation was notsignificant (r=0.40). This showed that crop water productivity could be better controlled by CT.Moreover, it was realized that the seven-day irrigation interval was far longer than required andpotatoes in all irrigation treatments were under water stress, especially in PRD, that mightpartially explain the 50% yield penalty of PRD compared to DI. The reason was that due to highatmospheric demand, soil water in the wet part of the root system would be completely depletedearlier by the time of next irrigation event. Conclusively, the CT is recommended as a morereliable crop water status and irrigation scheduling indicator than LWP in response to differentwater-saving irrigation managements.