Yu Sasada

Tokyo University of Agriculture and Technology, Edo, Tōkyō, Japan

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Publications (3)5.7 Total impact

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    ABSTRACT: Proper floodwater management during the cultivation period of paddy rice is essential for regulating the trade-off between methane and nitrous oxide emissions, as well as for saving irrigation water resource and maintaining crop productivity. To elucidate the effects of water saving irrigation (WS) and rice variety on different agro-environmental parameters such as CH4 and N2O emissions, global warming potential (GWP), greenhouse gases intensity (GHGI), carbon efficiency ratio, water use efficiency (WUE), rice growth and yield, a field experiment was conducted with two factors of split-plot design consisting of (1) main factor; WS (WS in which irrigation was withdrawn at soil Eh < −150 mV and kept 0–1 cm floodwater afterward) and continuous flooding (CF), and (2) sub-factor; a forage rice variety Leaf Star (LS) and a normal rice variety Kinuhikari (KN). Results showed that WS irrigation significantly (P < 0.05) mitigated CH4 emission by 65 % and \( {\text{GWP}}_{{{\text{CH}}_{ 4} + {\text{N}}_{ 2} {\text{O}}}} \) by 60 %, and enhanced WUE significantly (P < 0.01) by 180 % from that of CF. Carbon use efficiency of the grain and aboveground biomass carbon increased by 2.4 and 2.5 times, respectively, and GHGI was reduced by 3.1 times in WS. No significant differences were observed in the plant height, tiller number, rice biomass, N uptake and C accumulation between water treatments but the rice varieties: LS showed significantly (P < 0.05) higher values in these parameters than KN. This study highlighted that the WS is an effective measure for mitigating GWP, saving water while sustaining crop productivity.
    Full-text · Article · Jan 2015 · Paddy and Water Environment
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    ABSTRACT: Methane oxidation activity (MOA), methanotrophic bacteria (MOB), and CH4 emission in a paddy field fertilized with anaerobically digested slurry were compared between two varieties: a fodder rice variety Leaf star (LS) and a normal rice variety Kinuhikari (KN). Average MOA and MOB per unit dry root were significantly higher in KN (7.1 μmol g−1 CH4 g−1 dry root h−1 and 3.7 × 107 MPN g−1 dry root, respectively) than in LS (4.3 μmol g−1 CH4 g−1 dry root h−1, 2.1 × 107 MPN g−1 dry root), although MOA in the rice root per whole plant was not significantly different since root biomass of LS (1.5 g dry root plant−1) was significantly higher than that of KN (1.2 g dry root plant−1). MOA in the soil ranged from 0.031 to 0.087 μmol g−1 CH4 g−1 dry soil h−1, but there were no significant differences in both depths (0–5 and 5–15 cm) between the two rice varieties. MOA in the rhizosphere soil was significantly different between the rice varieties at flowering, but not at tillering. Methane emission in the field was lower and MOA and MOB in the rice root were higher in LS than in KN at tillering, but the reverse results were found at flowering and maturity stages. Total CH4 emission during a growing period was not significantly different between LS (27.4 ± 16.9 g CH4 m−2) and KN (24.0 ± 19.5 g CH4 m−2). There was a significant negative relationship between CH4 emission and rice root MOB (P P P
    No preview · Article · Dec 2011 · Paddy and Water Environment
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    ABSTRACT: We have examined the effects of different types of slurry on CH4 and N2O emissions, Zn and Cu contents of rice, and nitrate content of the drainage water. The experiment included four treatments: (1) anaerobically digested cattle slurry (ADCS), (2) ADCS filtered to remove the coarse organic matter fraction, (3) anaerobically digested pig slurry (ADPS), and (4) chemical fertilizer (CF). The application rate was 30 g NH4–N m−2. Different amounts of C were incorporated with fertilization: 725 g C m−2 in ADCS, 352 g m−2 in filtered ADCS, and 75 g m−2 in ADPS. The average CH4 emissions during a growing period were 304, 359, 452, and 579 mg m−2 day−1 in the CF, ADPS, filtered ADCS, and ADCS treatments, respectively. The CH4 emission was significantly higher in ADCS than in CF and ADPS. Negligible N2O emissions were observed during the growing period. Comparable concentrations of Zn and Cu were observed in the rice grain among the treatments. In contrast, their concentrations in the stems and leaves were significantly higher in ADPS than in CF treated rice, although the values were lower than the upper limit of feed additives. Nitrate concentrations in the drainage water were consistently low (0.5 mg N L−1). The present study suggested that ADPS, containing a lower amount of C than ADCS, might be an organic fertilizer in paddy field with comparable environmental impacts to chemical fertilizers (CF), but long-term field studies are needed to better understand the effects of these organic fertilizers.
    No preview · Article · Nov 2011 · Biology and Fertility of Soils