Abstract
Rice is a typical silicon-accumulating plant. Silicon (Si), deposited as phytoliths during plant growth, has been shown to occlude organic carbon, which may prove to have significant effects on the biogeochemical sequestration of atmospheric CO2. This study evaluated the effects of silicate fertilization on plant Si uptake and carbon bio-sequestration in field trials on China’s paddy soils. The results showed (1) Increased Si concentrations in rice straw with increasing application rates of silicate fertilizer; (2) Strong positive correlations between phytolith contents and straw SiO2 contents and between phytolith contents and phytolith-occluded carbon (PhytOC) contents in rice straw; (3) Positive correlations between the phytolith production flux and either the above-ground net primary productivity (ANPP) or the PhytOC production rates; (4) Increased plant PhytOC storage with increasing application rates of silicate fertilizer. The average above-ground PhytOC production rates during China’s rice production are estimated at 0.94 × 106 tonnes CO2 yr−1 without silicate fertilizer additions. However, the potential exists to increase PhytOC levels to 1.16–2.17 × 106 tonnes CO2 yr−1 with silicate fertilizer additions. Therefore, providing silicate fertilizer during rice production may serve as an effective tool in improving atmospheric CO2 sequestration in global rice production areas.
Highlights
IntroductionPhytolith-occluded carbon has been investigated in some plant species including grass[11] and forest[12] species, millet (Setaria italica)[13], bamboo[10], sugarcane (Saccharum sinensis)[14] and rice (Oryza sativa)[8]
The silica phytoliths that are formed occlude some of the organic carbon that is extracted from atmospheric CO2 during photosynthesis, which is deposited during plant growth[7]
Strong positive correlations were exhibited between phytolith-occluded carbon (PhytOC) content, based on straw dry weight, and phytolith or carbon content in phytolith (Fig. 4a,b). These results suggest that PhytOC concentrations based on dry weight are closely related to, phytolith content, and the efficiency of C deposition during phytolith formation in rice plants following silicate fertilizer additions
Summary
Phytolith-occluded carbon has been investigated in some plant species including grass[11] and forest[12] species, millet (Setaria italica)[13], bamboo[10], sugarcane (Saccharum sinensis)[14] and rice (Oryza sativa)[8] These previous trials have demonstrated the potential for long-term biogeochemical sequestration of atmospheric CO2 during plant phytolith production, with grass species’ phytoliths determined to be less degradable in soil, and over geological time, than phytoliths from leaves of forest species[6,15]. Due to the large production area, high above-ground net primary productivity (ANPP), and high Si accumulation, paddy rice cropping systems may play an important role, in terrestrial production of phytoliths[8], and in the sequestration of atmospheric CO2
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