Effects of Elevated Atmospheric CO2 Concentration and Water Regime on Rice Yield, Water Use Efficiency, and Arsenic and Cadmium Accumulation in Grain

Abstract

(1) Background: Elevated atmospheric CO2 concentration affects the growth and development of the rice crop. In Southern Brazil, rice is traditionally produced with continuous irrigation, implying a significant amount of water used. Besides, continuous flooding favors the uptake of toxic elements such as arsenic (As) and cadmium (Cd). In this work, one Brazilian rice cultivar (IRGA 424) was tested for the effects of elevated CO2 concentration and different water regimes on rice yield, and As and Cd accumulation in grain. (2) Methods: Rice was grown in two CO2 concentrations (400 and 700 µmol mol−1) and two irrigation regimes (continuous and intermittent). It was evaluated the number of tillers, plant height, aboveground dry weight (ADW), water use efficiency (WUE), rice yield components, and As and Cd concentration in rice grain. (3) Results: Rice plants were taller and had a higher WUE when cultivated at e[CO2]. The ADW and the rice yield component were not affected by CO2 levels nor water regimes. Intermittent flood regimes had a lower average As concentration. The Cd concentration in the samples in both growing seasons and all treatments was below the limit of quantitation (8.76 μg kg−1). (4) Conclusions: Enhanced CO2 concentration did not affect rice yield, increased the WUE, and reduced As concentration in grains. Regarding water management, the intermittent regime enhanced WUE and promoted a reduction in As concentration in grains.

Establishment of thresholds for alternate wetting and drying irrigation management in rice

“…Alternate wetting and drying had no effect on grain yield of evaluated hybrid cultivars including CLXL729, CLXL745, XP753 or inbred cultivars such as CL111, CL142-AR, CL151, CL181-AR, Cheniere, Presidio, and Jupiter (Atwill et al, 2018;Chlapecka et al, 2021;Massey et al, 2014;Reavis et al, 2021). Neither did irrigation threshold affect plant physiological parameters often associated with yield including evapotranspiration (ET), biomass, N uptake, agronomic efficiency of N (AEN), recovery efficiency of N (REN), internal efficiency of nitrogen, days to 50% heading, mature plant height, number of panicles, spikelet sterility, grains per 10 panicles, or 1000-grain weight (Atwill et al, 2018;Balbinot et al, 2021;Chlapecka et al, 2021;Reavis et al, 2021). Conversely, Massey et al (2014) noted that grain yield for the inbred cultivars CL131 and CL151 was 10.8% and 8.5% greater when managed under AWD than a constant 5-to 10-cm flood.…”