Straw incorporation is strongly recommended in rice paddy to improve soil quality and mitigate atmospheric carbon dioxide (CO 2), via increasing soil organic carbon (SOC) stock. However, straw application significantly increased methane (CH 4) emission during rice cultivation, and then its incorporation area was not expanded effectively. To find the reasonable straw management practice which can reduce CH 4 emission without productivity damage, the effect of straw incorporation season and method on CH 4 emission was investigated at six different textured paddy fields in South Korea for 2 years. A straw was applied right after rice harvesting in autumn, and the other right before rice transplanting in spring. In the autumn application, straw was applied with two different methods: spreading over soil surface or mixing with soil. Straw application significantly increased seasonal CH 4 flux by average 28-122% over 197-590 kg CH 4 ha −1 of the no-straw, but its flux showed big difference among straw applications. Fresh straw application before transplanting increased seasonal CH 4 flux by approximately 120% over the no-straw, but the autumn application reduced its CH 4 flux by 24-43% over 509-1407 kg CH 4 ha −1 of the spring application. In particular, the seasonal CH 4 flux was approximately 24% lower in straw mixing with soil after autumn harvesting than 423-855 kg CH 4 ha −1 in straw spreading over surface. However, CH 4 fluxes were not significantly discriminated by soil and meteorological properties in the selected condition. Straw application slightly increased rice grain yield by approximately 4% over the no-straw, but rice productivity was not statistically different among straw applications. Spring straw application increased CH 4 intensity which means seasonal CH 4 flux per grain yield by the maximum 220% over the no-straw. Autumn straw application significantly decreased CH 4 intensity by average 24-65% over the spring straw application. In particular, CH 4 intensity in straw mixing with soil treatment was not statistically different with the no-straw. Therefore, autumn straw application with mixing inner soil could be a reasonable straw management practice to decrease CH 4 emission impact with improving soil productivity.

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In order to ameliorate the poor charge transfer characteristics of hematite (α-Fe 2 O 3 ) photoanodes for photoelectrochemical (PEC) water splitting, heterojunction formation with p-CaFe 2 O 4 is attempted. Here, we report the in situ construction of a highly crystalline p-CaFe 2 O 4 shell on the surface of n-Ta:Fe 2 O 3 nanorods to form Ta:Fe 2 O 3 @CaFe 2 O 4 core−shell nanorod p−t−n heterojunction photoanodes with a transition layer (t) between them by a combined strategy of hybrid microwave annealing (HMA) and in situ Ta doping. The successful fabrication of the elaborate heterostructure is due to effective crystallization of p-CaFe 2 O 4 by HMA and prevention of Ca diffusion by already doped Ta atoms in hematite. The optimized Ta:Fe 2 O 3 @CaFe 2 O 4 photoanode loaded with the FeNiO x cocatalyst achieves a photocurrent density of 2.70 mA cm −2 , a low onset potential of 0.63 V RHE , and long-time stability in PEC water oxidation at 1.23 V RHE under 100 mW cm −2 solar irradiation, which represent marked improvements over bare hematite photoanodes and already reported hematite-based heterojunction photoanodes.