Effect of two whole-crop rice (Oryza sativa L.) cultivars on methane emission and Cu and Zn uptake in a paddy field fertilized with biogas slurry
Win, Aye Thida | Toyota, Koki | Ito, Daisuke | Chikamatsu, Seiya | Motobayashi, Takashi | Takahashi, Natsuko | Ookawa, Taiichiro | Hirasawa, Tadashi
A field experiment was carried out to evaluate the effect of two whole-crop rice (Oryza sativa L.) cultivars, TULT and Takanari, on methane (CH ₄) emission in a paddy field fertilized with biogas slurry (BS) at rates of 0 (NF), 100 (BS100) and 300 (BS300) kg nitrogen (N) ha ⁻¹, in comparison with chemical fertilizer CF100 (100 kg N ha ⁻¹). Takanari produced significantly higher biomass (P < 0.001) than TULT and showed significantly (P < 0.01) lower CH ₄ emission than TULT. BS applications caused higher CH ₄ emission (52 ± 27 and 80 ± 19 g m ⁻² in BS100 and BS300, respectively) than did CF100 (42 ± 18 g m ⁻²) and NF (28 ± 10 g m ⁻²) in TULT. In contrast, there was no significant difference in CH ₄ emission in Takanari among the treatments (26 ± 2, 26 ± 2, 32 ± 4, 29 ± 8 g m ⁻² in NF, CF100, BS100 and BS300, respectively). Methane oxidizing bacteria (MOB) showed significantly (P < 0.05) higher populations in Takanari than in TULT at harvest, which might be due to the higher root biomass (10.3 ± 2.2 g hill ⁻¹) in Takanari than in TULT (8.9 ± 1.8 g hill ⁻¹). MOB was significantly correlated with tiller number (R ² = 0.176*) and plant biomass (R ² = 0.242*). BS application showed higher copper (Cu) uptake in Takanari while it was not high in TULT. In contrast, it showed no difference in zinc (Zn) uptake in both varieties. Uptake of Cu was not different between the two varieties, while uptake of Zn in the grain was higher in TULT than in Takanari. The present study suggests that CH ₄ emission deriving from BS application in paddy field can be mitigated by selecting an appropriate cultivar, like Takanari. However, care should be taken for heavy metal uptake in selecting cultivars.
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