Language：English   Publishing type：Research paper (scientific journal)   Publisher：Irrigation and Drainage  

Alternate wetting and drying (AWD) irrigation is effective at reducing methane (CH4) emissions in rice cultivation. To investigate the effect of the infiltration rate on AWD effectiveness in terms of CH4 emissions, rice was cultivated in pots with three different infiltration rates under AWD. Under intermittent irrigation, the soil was more oxidative than is generally required for CH4 production (redox potential [Eh] > −150 mV), regardless of the infiltration rate. CH4 emission was suppressed by at least 37% compared to continuous flooding and no-infiltration conditions; however, temporarily elevated emission caused by drainage below saturation was observed 1–2 h after the flooding receded. This result is important for accurately determining CH4 emissions in water management techniques such as AWD. CH4 emissions during the heading stage, including temporarily elevated emissions after flooding receded, were greatest under the highest infiltration rate (18 mm day−1). The infiltration rate did not affect the rate of soil Eh reduction; however, the total organic carbon concentration in the drainage water suggested that more carbon, a methanogen substrate, migrated to the bottom of the pot with increasing infiltration rate, which likely increased CH4 emissions. This study will aid in the examination of ponding water management techniques to control CH4 emissions in rice production.

DOI： 10.1002/ird.2756

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：42nd Asian Conference on Remote Sensing, ACRS 2021  

Shiga Prefecture, Japan, is one catchment that constitutes a large basin surrounded by mountains such as Mt. Hiei, Mt. Hira, Mt. Ibuki, Gozaishodake and Suzuka Mountains. In the center, there is Lake Biwa occupying one-sixths of the total area of the prefecture. Lake Biwa has been a precious water source for Osaka and Kyoto. We created a landscape image of the entire catchment by overlaying the SRTM_DEM image measured by the space shuttle Endeavor in 2000 and Landsat image. From this image, we attempted to forecast the impacts on the regional environments due to the wind trail crossing Lake Biwa, microclimates along the lake coast, training at the time of typhoon visit, development of a large-scale housing complex, mega solar power plant project, and so on. In order to foresee the regional environments and disaster risks, we believe that an extensive systematic structure including hydrology, remote sensing and geographic information system becomes necessary from now on. Considering the disastrous cases in the recent several years in Japan such as landslides and flooding engulfing houses, understanding of detailed landscape architectures in each region is strongly encouraged from the standpoint of risk management when construction of a mega solar power station or a large-scale housing complex is planned on a slope of a mountain or a wetland regarded as a retarding basin.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：農業土木学会   Participation form：Joint(The main charge)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：農業土木学会   Participation form：Joint(The main charge)  

Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Fukushima  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Fukushima  

Sub-surface irrigation hoses were made of fire hoses pierced with a sewing machine needle, and its performances were compared with that of conventional surface irrigation in the cultivation of Komatsuna, a Japanese leafy vegetable. The results showed that the total water supply of sub-surface irrigation was significantly lower than that of surface irrigation (62%) at the 5% significance level, and the water use efficiency was 1.38 times better. Therefore, by controlling the water pressure in the hose, we were able to grow leafy vegetables without water stress. Although the water supply intensity for sub-surface irrigation corresponded to the water pressure inside the hose, there were some problems such as algae clogging inside the hose.

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Kagoshima  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：Kagoshima  

AWD is a method to reduce methane production without yield loss by started from one to two week after transplanting repeated intermittent irrigation after seeding and during all but the flowering period. However, there are no examples of detailed investigations of soil environmental changes during AWD. In this study, methane emission, ORP, moisture content, and temperature were measured in potted rice plants. It was found that the presence and growth stage of rice plants affected the amount of methane released as well as the ground temperature.