Irrigation Department, Faculty of Agriculture, Shiraz University
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 Ramos potato cultivars. Canopy temperature (CT) and leaf water potential (LWP) were assessed as the potential 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, DI and PRD irrigation treatments. The LWP and CT values were not significant between the two potato cultivars during the measurements, but CT was frequently significant between the irrigation treatments such that the PRD treatments were significantly 5 and 2 oC warmer than FI and DI treatments, respectively. Higher CT in PRD caused significant yield penalty such that DI and FI produced almost two times higher fresh tuber yield. Analysis revealed that CT had significantly higher correlation (r=0.66) with water productivity (weight of fresh tuber yield divided by volume of applied irrigation water) than LWP, which its correlation was not significant (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 and potatoes in all irrigation treatments were under water stress, especially in PRD, that might partially explain the 50% yield penalty of PRD compared to DI. The reason was that due to high atmospheric demand, soil water in the wet part of the root system would be completely depleted earlier by the time of next irrigation event. Conclusively, the CT is recommended as a more reliable crop water status and irrigation scheduling indicator than LWP in response to different water-saving irrigation managements.