A potential CO carrier to improve the utilization of HCO by plant-soil ecosystem for carbon sink enhancement.

INTRODUCTION

Improving the rhizospheric HCO utilization of plant-soil ecosystem could increase the carbon sink effect of terrestrial ecosystem. However, to avoid its physiological stress on the crop growth, the dosage of HCO allowed to add into the rhizosphere soil was always low (i.e., <5-20 mol/m).

OBJECTIVES

To facilitate the utilization of relatively high concentrations of HCO by plants in the pursuit of achieving terrestrial carbon sink enhancement.

METHODS

In this study, the feasibility of directly supplementing a high concentration HCO carried by the biogas slurry to the plant rhizosphere was investigated using the tomato as a model plant.

RESULTS

The CO-rich biogas slurry was verified as a potential CO carrier to increase the rhizospheric HCO concentration to 36 mol/m without causing a physiological stress. About 88.3 % of HCO carried by biogas slurry was successfully fixed by tomato-soil ecosystem, in which 43.8 % of HCO was assimilated by tomato roots for the metabolism, 0.5 ‰ of HCO was used by microorganisms for substances synthesis of cell structure through dark fixation, and 44.4 % of HCO was retained in the soil. The rest of HCO (∼11.7 %) might escape into the atmosphere through the reaction with H. Correspondingly, the carbon fixation of tomato-soil ecosystem increased by 150.1 g-CO/m-soil during a tomato growth cycle. As for the global countries that would adopt the strategy proposed in this study to cultivate the tomato, an extra carbon sink of soil with about 1031.1 kt-C per year (i.e., an additional 0.21 tons of carbon per hectare soil) could be obtained.

CONCLUSION

This would be consistent with the goal of soil carbon sink enhancement launched at COP21. Furthermore, the regions with low GDP per capita may easily achieve a high reduction potential of CO emissions from the agricultural land after adopting the irrigation of CO-rich biogas slurry.