Growth, phenological, and yield response of upland rice (Oryza sativa L. cv. Nerica 4®) to water stress during different growth stages

• Published in: Agricultural water management 2018-02, Vol.198, p.39-52
• Main Authors: Alou, I.N., Steyn, J.M., Annandale, J.G., van der Laan, M.
• Format: Article
• Language: English
• Subjects: Delayed development; NERICA; Plant available water; Thermal time; Water stress; Water use efficiency
• ISSN: 0378-3774; 1873-2283
• DOI: 10.1016/j.agwat.2017.12.005

•Water stress during early reproductive stage increases thermal time to maturity.•Delaying of flowering and anthesis is not dependent on tiller abortion.•Spikelet sterility with stress during tillering is due to limited assimilate availability.•Recover ability and highly elastic growth is characteristic of early reproductive stress.•Considerable water savings without substantial yield penalty is possible in some stages. Rice (Oryza sativa L.) grown in uplands is exposed to variable soil water conditions and unpredictable periods of water stress (WS). The study was conducted to determine the impacts of WS imposed at different phenological stages of upland rice on growth, phenology, recovery of source size, yield and water use efficiency (WUE). The popular cv. Nerica 4® grown in Africa was sown under a rain-out shelter for two seasons. Treatments included a well-watered control (CT) and stress imposed by withholding water for the duration of different stages: tillering (Ti), panicle initiation (PI), anthesis (AT) and grain filling (GF). Name codes used for treatments were thus: CT, STi, SPI, SAT and SGF. When water was withheld, soil water content in the 0–0.6 m soil layer dropped to approximately 50% of plant available water, while stomatal conductance of the abaxial leaf surface and leaf area index decreased significantly, suggesting that severe stress was experienced. Growing degree days to reach the different growth stages were roughly equal in both seasons, even though sowing was in the mid-summer of 2013/2014 and early summer of 2014/2015, respectively. Time to reach peak tillering could not be explained by temperatures and cumulative solar radiation during growth. The onset of reproduction was highly significantly (p