Soil carbon budget in a single-cropping paddy field with rice straw application and water management based on soil redox potential.

摘要

An ideal state for agroecosystems to mitigate global warming should include both decreasing CO< sub>2 and CH< sub>4 emissions and increasing soil carbon storage. Two-year field experiments were carried out to examine the effects of water management (continuous flooding [CF] and Eh control [EH]) and rice straw management (application [+S] and removal [-S]) on the soil carbon budget in a single-cropping paddy field in Japan. The EH water management based on soil redox potential that the authors have proposed decreased the total CH< sub>4 emission during the rice growing period compared with CF. The +S increased CO< sub>2 emission as soil respiration during the non-flooded fallow period compared with -S, but also increased straw residues in the soil. However, there was little evidence for sequential carbon accumulation in the soil over the year by +S. The resultant annual budget of soil carbon was a loss of 32-103 g C m-2 in the EH+S treatment compared with a loss of 166-188 g C m-2 in the CF-S treatment. Taking into account the global warming potentials, the EH+S treatment also decreased the total CO< sub>2-equivalent emission compared with the CF-S treatment. Consequently, a combination of appropriate water management and straw application will be an effective option in decreasing both CO< sub>2-equivalent emission and sustaining soil carbon storage.