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2 results on '"Toshiyuki Mochida"'

1. Factors controlling available soil nitrogen in Japanese paddy fields.

Author

Yuri Ichinose, Yuta Ise, Takashi Kanda, Yuji Maejima, Tetsuo Yagi, Yoshinori Takahashi, Shinpei Nakagawa, Kiyomi Kamiyama, Hirokuni Iwasa, Ayako Kadokura (Kaneko), Yoshinori Ohashi, Shigeo Komatsu, Minoru Matsuyama, Yusuke Hirayama, Toshiyuki Mochida, Kayo Matsui, Takahiro Takimoto, Hiroshi Obara, Hideo Kubotera, and Yusuke Takata

Subjects
PADDY fields, NITROGEN in soils, SOIL temperature, SOIL texture, SOIL classification, HYPEREUTECTIC alloys
Abstract

Available soil nitrogen (Av-N) is an important indicator for understanding the soil fertility in paddy fields. Previous studies have reported a decline in Av-N resulting from paddy-upland rotation at a regional scale in Japan, while the factors influencing this phenomenon on a national scale are not well understood. This study aims to assess the effects of soil temperature, land use, soil type and soil texture on Av-N in paddy fields across Japan. Soil surveys were conducted in 13 prefectures in 2020 and 2021, involving the collection of soil samples from the plow layer in a total of 2,600 paddy fields. Our results revealed that soil temperature had the most significant influence on Av-N, followed by land use and soil type. Av-N exhibited a negative correlation with soil temperature, whereby the average Av-N in the thermic soil temperature regime (>15°C, Av-N: 107 ± 48 mg kg-1) significantly lower than that in the mesic soil temperature regime (≤15°C, Av-N: 166 ± 74 mg kg-1). Increased upland frequency in paddy fields led to a decrease in Av-N, particularly pronounced in the thermic soil temperature regime, while partially mitigated in the mesic soil temperature regime. In the thermic soil temperature regime, paddy fields with long-term upland usage (upland frequency of paddy fields was more than 50%) had an average Av-N of 50 mg kg-1, necessitating additional organic matter application. Furthermore, the results concerning soil type and soil texture indicated that Av-N was higher in wet soil compared to semi-wet soil, and fine-textured soil had higher Av-N than medium-course textured soil. These findings underscore the negative effect of accelerated drying in paddy fields due to the expanding practice of paddy-upland rotation, leading to decreased Av-N. In conclusion, our study proposes the importance of organic matter management practices, with a primary emphasis on soil temperature, further refined by considering land use and soil type, to ensure the maintenance of adequate Av-N levels in paddy fields in Japan. [ABSTRACT FROM AUTHOR]

Published
2023
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2. Mitigation of methane emissions from paddy fields by prolonging midseason drainage

Author

Nanako Yoshikawa, Yutaka Shiratori, Yasufumi Suzue, Kazuyuki Yagi, Shigeto Sudo, Takahiro Yoshida, Masayuki Itoh, Toshiyuki Mochida, Shinobu Suga, Shizuka Mori, Hiroshi Saito, and Hiroyuki Mizukami

Subjects
Methane emissions, chemistry.chemical_classification, Ecology, Methanogenesis, Nitrous oxide, Methane, chemistry.chemical_compound, chemistry, Environmental chemistry, Grain yield, Paddy field, Environmental science, Animal Science and Zoology, Organic matter, Drainage, Agronomy and Crop Science
Abstract

In order to analyze the mitigation of methane (CH 4 ) emissions and the global warming potentials (GWPs) of CH 4 and nitrous oxide (N 2 O) emissions from paddy fields by modifying the adopted water-management technique, we conducted field experiments to measure the CH 4 and N 2 O fluxes at nine sites across Japan. Over 2 years, we tested different water-management strategies such as prolonged midseason drainage (MD) in each site. The CH 4 emission rates at each site varied considerably; the rates were dependent on the ratio of reductive and oxidative capacities of the fields. Seasonal CH 4 emission was effectively reduced at most sites by prolonging MD beyond its conventional duration, especially at sites where organic matter was added to the soil before the cultivation. We attribute this result to the effective suppression of the CH 4 emission peak that occurs early in the cultivation period. Despite the large variation in seasonal CH 4 emissions among the sites, the rate of CH 4 emission resulting from alternative water-management strategies relative to that resulting from conventional water-management strategies is highly dependent on the degree of drainage during the MD period. N 2 O emission at most sites, in terms of GWP-based CO 2 -equivalent, was much smaller than that of CH 4 emission. Compared to conventional water-management strategies, the seasonal CH 4 emissions and the net 100-year GWPs (CH 4 + N 2 O) can be suppressed to 69.5 ± 3.4 (SE)% and 72.0 ± 3.1% while maintaining grain yields as high as 96.2 ± 2.0% by prolonging MD on average by employing the selected alternative water-management strategies that satisfied the following conditions: the percent of CH 4 emission of alternative water-management strategies was less than 90% and the grain yield was greater than 85% relative to conventional water-management strategies.

Published
2011

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