Effects of deficit irrigation (DI) and partial root drying (PRD) on gas exchange, biomass partitioning, and water use efficiency in potato

The effect of ‘partial root drying’ (PRD) compared with other irrigation strategies, viz. full irrigation (FI) and deficit irrigation (DI), on morphological and physiological characteristics of potato (Solanum tuberosum L. cv. Folva) were investigated at tuber initiation stage. Potatoes were grown in pots with roots split equally between two soil columns. In FI, the whole root system was irrigated at 100% of evapotranspiration (ETfull); in DI 50% of ETfull was irrigated to the whole root system; in PRD 50% of ETfull was irrigated to one soil column while the other was allowed to dry, and irrigation was shifted when 80–85% of plant available water in the dry side had been used. Midday leaf water potential was similar for all treatments at 9 days after onset of treatments (DAT), while it was significantly lower in PRD than in FI and DI plants at 21 DAT. Photosynthesis, stomatal conductance, and transpiration were generally greater in FI plants. Compared to FI, both DI and PRD significantly decreased leaf area and biomass. DI decreased biomass allocation to leaves and stems while increasing it into roots and tubers. PRD increased biomass allocation to roots. ET under PRD was ca. 80% of DI and FI until six DAT, thereafter ET of DI and PRD was similar and was significantly less than that of FI. Water use of DI and PRD plants was 37% less than that of FI. Water use efficiency (WUE) and transpiration efficiency were similar for PRD and FI plants, and were significantly less than those of DI plants. Conclusively, given the same amount (50% of ETfull) of irrigation, PRD has no advantages compared to DI in terms of biomass production and WUE in potato at tuber initiation stage.