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),<br />deficit (DI) and partial root drying (PRD) irrigation strategies were applied in Agria and Ramos<br />potato cultivars. Canopy temperature (CT) and leaf water potential (LWP) were assessed as the<br />potential tools for irrigation scheduling during the vegetative and productive growth stages.<br />LWP varied between ca. -1.4 and -1.6 MPa and was not significantly different between FI, DI<br />and PRD irrigation treatments. The LWP and CT values were not significant between the two<br />potato cultivars during the measurements, but CT was frequently significant between the<br />irrigation treatments such that the PRD treatments were significantly 5 and 2 oC warmer than FI<br />and DI treatments, respectively. Higher CT in PRD caused significant yield penalty such that DI<br />and FI produced almost two times higher fresh tuber yield. Analysis revealed that CT had<br />significantly higher correlation (r=0.66) with water productivity (weight of fresh tuber yield<br />divided by volume of applied irrigation water) than LWP, which its correlation was not<br />significant (r=0.40). This showed that crop water productivity could be better controlled by CT.<br />Moreover, it was realized that the seven-day irrigation interval was far longer than required and<br />potatoes in all irrigation treatments were under water stress, especially in PRD, that might<br />partially explain the 50% yield penalty of PRD compared to DI. The reason was that due to high<br />atmospheric demand, soil water in the wet part of the root system would be completely depleted<br />earlier by the time of next irrigation event. Conclusively, the CT is recommended as a more<br />reliable crop water status and irrigation scheduling indicator than LWP in response to different<br />water-saving irrigation managements.