Carbon distribution and dynamics under brittle straw incorporation and different water management schemes: a microcosm incubation study

Rising atmospheric greenhouse gases (GHGs), including CO2, CH4, and N2O, potentially accelerate climate change and global warming in the climate system. Straw incorporation has been considered an environmentally friendly practice that can simultaneously allevate these environmental issues and improve soil qualities (e.g., soil health). However, direct incorporation is not well adapted in paddy rice fields by local farmers because the fallow period between cropping season is often too short (i.e., 3O days) to allow sufficient decomposition of straw residue. The incomplete residue decomposition is likely to interfere with the growth of the following crops, resulting from nutrient immobilization, production of harmful organic acids, and pest/disease outbreak. Recently, the brittle straw of (Oyza sativa L var. IR64) showed great potential because of its fast-decomposed characteristics under the anaerobic (continuous flooding, CF) condition. Despite decades of promotion for alternative wetting and drying (AWD) to mitigate CH4 emissions from paddy soils, this brittle mutant has not been evaluated. Thus, this study investigated the confounding effects of the brittle straw incorporation under two water regimes (CF vs. AWD on carbon (C) dynamics among the phases of gas (GHGs), liquid (dissolved organic/inorganic carbon, DOC and DIC), and solid (soil aggregates fractionation) for two soil types (course- vs. fine-texture) using a microcosm incubation experiment. Results showed that the CF treatments predominantly had higher CH4 flux than other treatments. Meanwhile the increased CO2, flux from BRS-AWD started to reduce on the 20th day after straw incorporation (DAI) than NBRS-AWD in both soils. Higher NO3-N mineralization and dissolved organic nitrogen (DON) resulted in higher N2O flux under the BRS-AWD however, N2O flux under the BRS-AWD however, N2O flux was ngeligible in both soils. Conclusively, the BRS-AWD treatment likely reduced the overall GHG emissions and improved NO3-N, PO4 sup -3, and exchangeable K mineralization compared to the NBRS-AWD treatment.