Testing nitrogen and water co-limitation of primary productivity in a temperate steppe

Background and aims

Studies have found significant differences in methane (CH₄) emissions among rice cultivars; however, it is unclear whether this difference is related to radial oxygen loss (ROL) from the roots.

Methods

Based on a 2-year in situ field study and solution culture experiments on 16 rice cultivars, we investigated CH₄ emission levels and their dependence on ROL.

Results

We detected significant differences in CH₄ emission and ROL among rice cultivars. The lowest and highest CH₄ emission levels were 4.10 and 7.35 g m^?2 for early rice, and 14.36 and 23.33 g m^?2 for late rice, respectively. The maximum and minimum ROL values were 3.77 and 1.73 mmol plant^?1 h^?1 for early rice, and 4.18 and 2.08 mmol plant^?1 h^?1 for late rice, respectively. Seasonal total CH₄ emission was negatively correlated with ROL in the early rice season (p?<?0.01), and (p?<?0.01) in the late rice season. ROL was positively correlated with the number of roots per plant (RN), root tips per plant (RT), and root volume per plant (RV).

Conclusions

We suggest that ROL can be used as a predictive index for CH₄ emissions. RN, RT, and RV were the most important factors influencing ROL in rice cultivars.