Comparison of phytolith-occluded carbon in 51 main cultivated rice (Oryzasativa) cultivars of China

In this study, the carbon (i. e., C) bio-sequestration within phytoliths (PhytOC) in 51 rice cultivars was evaluated to breed cultivars with a high efficiency of carbon sequestration in phytoliths and high productivity. The phytolith extraction from rice plants was achieved through wet digestion procedures, and the C content of phytoliths was determined using an Elemental Analyzer 3000. The phytolith contents in the rice organs ranged from 9.69 to 175.52 mg g(-1), with significant differences in the phytolith contents in the different organs of each rice cultivar. The estimated PhytOC fluxes of rice plants in 51 rice cultivars were approximately 0.006-0.035 Mg-e-CO2 per ha per year. High variation coefficients of phytoliths and contents of phytoliths of plant in indica and japonica rice cultivars implied considerable variation among these rice cultivars. Additional results showed no correlation between the phytolith contents and the C content of phytoliths (R = 0.170, p > 0.05), and the C content of phytoliths was significantly correlated with the PhytOC content in dry plant weight (R = 0.804, p < 0.01). However, the estimated PhytOC flux was significantly correlated with the phytolith content (R = 0.651, p < 0.01), with the C content of phytoliths (R = 0.512, p < 0.01) and with the PhytOC content in dry plant weight (R = 0.727, p < 0.01). Selected rice cultivars herein with a high efficiency of C sequestration in phytoliths and high productivity, therefore, played important roles in controlling the C sink and Si biogeochemical cycle in soil-rice systems.