Effects of Forage Rice Cultivation on Carbon and Greenhouse Gas Balances in a Rice Paddy Field

摘要

The effects of conversion from staple rice to forage rice on carbon and greenhouse gas (GHG) balances in a paddy field were evaluated. A staple rice plot without the application of livestock manure compost (LMC, S ? M plot) and forage rice plots with and without the application of LMC, derived mainly from cattle (2 kg?FW m ?2 , F + M and F ? M plots, respectively), were established. CH 4 and N 2 O fluxes and CO 2 flux from a bare soil plot for organic matter decomposition (OMD) were measured. The carbon budget was calculated by subtracting the OMD, CH 4 emission, and harvested grain and straw (forage rice only) from the net primary production and LMC. The net GHG balance was calculated by integrating them as CO 2 equivalents. There were no significant differences in GHG flux among the plots. Compared to the carbon loss in the S ? M plot, the loss increased by harvesting straw and was mitigated by LMC application. The net GHG emission in the F + M plot was significantly lower than that in other plots (1.78 and 2.63?2.77 kg CO 2 -eq m ?2 year ?1 , respectively). There is a possibility that GHG emissions could be suppressed by forage rice cultivation with the application of LMC.