Paddy soil makes up the largest anthropogenic wetlands on Earth and has been proposed to have a great potential in sequestrating atmospheric CO₂. Fertilizer amendment is an important approach for increasing CO₂ sequestration in cropland soils.

Carbon dioxide (CO₂) assimilation by autotrophic bacteria in the soil carbon cycle contributes to a reduction in the concentration of atmospheric CO₂ which accounts for about 50% of the current global warming threat. While, the long-term impact of fertilizer on CO₂ assimilation in the bacterial community of paddy soils remains poorly understood.

To narrow this knowledge gap, researchers in the Institute of Subtropical Agriculture, Chinese Academy of Sciences (ISA) collected different fertilizer treated paddy soils (no fertilizer(CK), chemical fertilizers(NPK) and NPK combined with rice straw(NPKM)) from three long-term fertilization experiment stations. And using molecular approaches including terminal restriction fragment length polymorphism and quantitative PCR of the cbbL gene (encodes for RubisCO), researchers had identified the impacts of Long-term field fertilization on the activity and community of CO₂-assimilating bacteria.

“Long-term fertilization strongly affects the activity and community of the cbbL-containing bacterial populations in paddy soils and straw incorporation treatment has the most positive effect.” said Yuan Hongzhao, a doctoral researcher at ISA and first author on the paper. In all stations, cbbL-containing bacterial communities are dominated by facultative autotrophic bacteria. The bacterial cbbL abundance and RubisCO activity determined in paddy soils are significantly positively correlated, and both increased with the addition of fertilizer. Among the measured soil parameters, soil organic carbon and pH were the most significant factors influencing the community composition, abundance and activity of the cbbL-containing bacteria.

“Besides, our work from these long-term experiment stations shows that the mean amount of SOC in paddy soils increased by 1.67 times during the period between 1979 and 2003. Hence, we would hypothesize that the application of fertilizer favors the growth of such microorganisms and may result in increased C sequestration in paddy soils. ”said Yuan.

This research was financially supported by funds from the Chinese Academy of Sciences (No. XDA05050505), the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. ISACX-LYQY-QN-1103) and the National Natural Science Foundation of China (No. 40901124, 41090283, 40801098).

The study entitled “Long-term field fertilization alters the diversity of autotrophic bacteria based on the ribulose-1,5-biphosphate carboxylase/oxygenase (RubisCO) large-subunit genes in paddy soil” has just been published online in Applied Microbiology and Biotechnology, details could be found at http://www.springerlink.com/content/r4073451w32471t7/.