Carbon flux from decomposing ~(13)C-labeled transgenic and nontransgenic parental rice straw in paddy soil

摘要

Purpose Genetic modification of Bt rice may affect straw decomposition and soil carbon pool under flood conditions. This study aims to assess the effects of cry gene transformation in rice on the residue decomposition and fate of C from residues under flooded conditions. Materials and methods A decomposition experiment was set up using ~(13)C-enriched rice straws from transgenic and nontransgenic Bt rice to evaluate the soil C dynamics and CH_4 or CO_2 emission rates in the root and non-root zones. The concentrations and stable carbon isotope compositions of the soil organic carbon (SOC), dissolved organic carbon (DOC), microbial biomass carbon (MBC), CH_4, and CO_2 of the root and non-root zones were determined from 7 to 110 days after rice straw incorporation. Results and discussion Rice straw incorporation into soil significantly increased the SOC, DOC, and MBC concentrations and the CH_4 and CO_2 emission rates. The percentage of ~~(13)C-SOC remaining in the root zone was significantly lower than that in the non-root zone with rice straw decomposition. The DOC and MBC concentrations significantly increased in both the root and non-root zones between 0 and 80 days after rice straw incorporation. However, no significant differences were found after Bts (Bt rice straw added into soil) and Cks (nontransgenic Bt rice straw added into soil) incorporation in the root and non-root zones. This result may be attributed to the priming effects of sufficient oxygen and nutrients on straw degradation in the root zone. Conclusions Bt gene insertion did not affect the SOC, DOC, and MBC concentrations and the CH_4 and CO_2 emission rates in both the root and non-root zones. However, rice straw incorporation and root exudation significantly increased the SOC, DOC, and MBC concentrations and the CH_4 and CO_2 emission rates.