Preliminary investigation on crop growth, physiology, and yield of rice under partial root-zone irrigation

Rice is a staple food predominantly consumed by more than half of the global population. Water deficit is a crucial threat to produce rice globally. Prevailing water-saving techniques for rice can reduce water inputs but are not widely adopted due to the high yield penalty. Partial root-zone irrigation (PRI) is an innovative water-saving technique that allows simultaneous wet and dry areas within the root zone. We hypothesized that optimized PRI improves the water use and reduces the yield penalty of rice. A split root experiment was conducted on rice grown in pots with six defined PRI treatments, that is, PRI₁, PRI₂, PRI₃, PRI₄, PRI₅, and PRI₆. Half of the root system was wetted and alternated between halves with one- (PRI₁), two- (PRI₂), three- (PRI₃), four-(PRI₄), five- (PRI₅), and six- (PRI₆) day intervals. Conventionally irrigated rice plants where the whole root zone of rice was wetted and grown in the nonsplit pot were maintained and considered as control. Control and PRI treatments were irrigated based on 100% potential evapotranspiration demand (ETc). In particular, one PRI treatment (PRI₃) showed a remarkable increase in active roots and leaf photosynthesis (P_N) by wet and dry cycles within the root zone. Distinctive shoot responses of rice under PRI indicated enriched physiological responses for superior water productivity. The third-day-interval partial root-zone irrigation (PRI₃) and conventional irrigation had similar leaf water potential (Ψ_leaf ), while PRI₃ had higher grain yield than conventional treatment and higher root surface area that may have compensated for the moderate level of stress in PRI. The finding that PRI scheduled at three-day intervals (PRI₃) was superior to conventional irrigation for a single rice plant is promising and needs to be tested and adapted to field conditions.