Investigation of Partial Root-zone Irrigation (PRI) on Growth, Leaf Gas Exchange, Water Productivity and Yield of Rice (Oryza sativa L.)

Efficient water use in rice has become an imperative issue. Prevailing water saving techniques can reduce water inputs but are not widely adopted due to yield loss. Partial Root-zone Irrigation (PRI) is a new water saving technique that allows water simultaneously within wet and dry areas of root zone. PRI has been implemented in many crops apart from rice that has to be tested. PRI experiment was performed on rice roots using split pots with six defined PRI treatments (partial root system irrigated and alternated on one-six days interval [PRI₁- PRI₆]). Conventional irrigation (whole root zone irrigation in a non-split pot) and PRI treatments were imposed based on 100 % potential evapotranspiration demand. The wet and dry cycles by PRI showed diverse change in rice growth, physiology and yield. Among the PRI treatments, PRI₃ showed optimal growth attributes, favourable root plasticity, altered leaf gas exchange, increased photosystem efficiency, improved yield and water productivity. A remarkable reduction in average root diameter at PRI₃ revealed active root system. Higher leaf photosynthesis (P_N) and transpiration (T_r) of PRI₃ plants indicated the better balance between stomatal conductance (g_s) and leaf water potential (Ψ_leaf). PRI₃ improved the grain yield by 12.4 % (P=0.01) and water productivity by four-fold (P=0.05) compared to conventional method. The result supported increased water productivity and yield thorough distinctive root and shoot responses in PRI_3. Overall, partial root-zone irrigation at three-day interval might be an efficient irrigation system to increase rice production with ample amount of water.