Abstract
Increase in atmospheric CH4, a greenhouse gas, is a cause of global warming, and rice paddies are one of major emission sources of CH4. Effects of the number of seedlings per hill (1, 3, 5, and 7) and the spacing between hills (15×15 cm, 15×30 cm, 30×30 cm) of rice plants on CL emissions from a paddy field were examined. A significant difference in total CL emission was observed between the treatments with difference in the number of seedlings per hill, and the transplanting of 7 seedlings per hill resulted in the lowest CH4 emission among the four treatments. When the spacing between hills was altered, the total CH4 emission was smaller in the treatment with 15×15 cm spacing than in the other two treatments. The number of tillers and plant biomass did not explain the differences in CH4 emission between the treatments. Less difference in grain yield among the treatments indicated that a larger number of seedlings per hill (7 or 5) or a narrower spacing between hills (15×15 cm) was effective for reducing CL emission without decreasing the yield.
