Carbon occlusion potential of rice phytoliths: Implications for global carbon cycle and climate change mitigation

Abstract

Phytoliths are silica bodies produced by plants through bio-mineralization process. During such process, occlusion of carbon (C) also takes place within the phytoliths called phytolith occluded C (PhytOC). The PhyOC is highly stable and may substantially contribute to long-term terrestrial C sequestration. The present study aimed to investigate the phytolith and PhytOC contents variability in rice cultivars and its potential for long-term terrestial C biosequestration.The results indicate that dry matter yield of rice cultivars varied from 15.52 to 28.82 g plant-1and, the PhytOC contents of straw, root, husk, and grains range from0.22-0.68%, 0.09-0.22%, 0.43-0.82% and 0.002-0.024%, respectively. The PhytOC content of rice depends on the content of phytoliths and the efficiency of C occlusion within the phytoliths. The C sequestration rates of rice cultivars are approximately 0.05 - 0.12 Mg of C dioxide equivalents (Mg-e-CO2) ha-1 year-1. Assuming maximum phytolith C biosequestration rate of 0.12 Mg-e-CO2 ha-1 year-1, the global annual potential sink rate of PhytOC in soils through rice phytoliths would approximately be 16.4 Tg-e-CO2. Therefore rice crop may play a significant role in long-term C sequestration through PhytOC.