Evaluation of the occluded carbon within husk phytoliths of 35 rice cultivars

Rice is a well-known silicon accumulator. During its periods of growth, a great number of phytoliths are formed by taking up silica via the plant roots. Concurrently, carbon in those phytoliths is sequestrated by a mechanism of long-term biogeochemical processes within the plant. Phytolith occluded C (PhytOC) is very stable and can be retained in soil for longer than a millennium. In this study, we evaluated the carbon biosequestration within the phytoliths produced in rice seed husks of 35 rice cultivars, with the goal of finding rice cultivars with relatively higher phytolith carbon sequestration efficiencies. The results showed that the phytolith contents ranged from 71.6 mg∙g‒1 to 150.1 mg∙g‒1, and the PhytOC contents ranged from 6.4 mg∙g‒1 to 38.4 mg∙g‒1, suggesting that there was no direct correlation between the PhytOC content and the content of rice seed husk phytoliths (R = 0.092, p>0.05). Of all rice cultivars, six showed a higher carbon sequestration efficiency in phytolith seed husks. Additionally, the carbon biosequestration within the rice seed husk phytoliths was approximately 0.45‒3.46 kg-e-CO2∙ha‒1∙yr‒1. These rates indicate that rice cultivars are a potential source of carbon biosequestration which could contribute to the global carbon cycle and climate change.