Intermittent Irrigation Enhances Morphological and Physiological Efficiency of Rice Plants

The response of rice roots and shoots and their causal relationships affecting yield under varying soil water condition are important related subjects of research. To understand the mechanism of response, studies were conducted using four water treatments: a) intermittent flooding through the vegetative stage (IF-V); b) intermittent flooding extended into the reproductive stage (IF-R); c) no standing water (NSW), maintaining soil at field capacity; and d) continuous flooding (CF) condition at the Asian Institute of Technology in Thailand.

It was observed that the senescence of lower leaf and flag leaf was delayed under IF-V compared to CF water condition. This delay was associated with higher root oxidizing activity (ROA) rate (50% higher than CF), higher root length density (RLD) (52% higher than CF), higher biomass production (14% higher than CF) along with higher grain yield (25% higher than CF). The plants grown under NSW conditions had better growth at later growth stage and better yield performance compared to IF-R because of higher nitrogen availability and higher uptake rate under NSW water conditions (73% higher N uptake). However, under CF water condition the nitrogen availability was not a limiting factor but due to decreased root activity rate the dry matter production and grain yield significantly reduced compared to IF-V water condition.

The results suggested that ROA and RLD are linked to shoot response and to dry matter production. A better understanding of the underlying mechanisms should assist in achieving improvements in crop productivity through improved crop management practices in water-limiting environment.