Jōetsu, Japan
Jōetsu, Japan

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Chiba M.,Natlagric Res Center | Chiba M.,Niigata University | Matsumura O.,Natlagric Res Center | Terao T.,Natlagric Res Center | And 2 more authors.
Japanese Journal of Crop Science | Year: 2011

Suppression of the occurrence of chalky grains caused by a high temperature at the ripening stage of rice is an urgent issue in rice production in Japan. Deep flood irrigation with a water depth of 18 cm is an effective measure to avoid the occurrence. However, the area of paddy fields that can keep this level of water depth is limited, because the plants are usually not so high. Here, we examined the effects of flood irrigation at a water depth of 10 cm and deep planting (depth of 6 cm), and their combination on the yield and quality of rice using cultivars Hatsuboshi and Koshihikari which are sensitive and moderately tolerant to a high temperature at the ripening stage, respectively. In Hatsuboshi, deep planting combined with 10-cm irrigation from the rooting stage to the maximum tillering stage reduced the occurrence of chalky grains without yield reduction that was caused by an 18 cm flood irrigation. In Koshihikari, 18-cm flood irrigation was the best to reduce chalky grains, but 10-cm flood irrigation also reduced chalky grains significantly without significant yield reduction. Deep flood irrigation (18 cm) decreased the redox potential of soil, but did not damage the root system at the ripening stage. In addition deep flood irrigation did not reduce soil-bearing capacity, and was not considered to prevent combine harvesting.


Chiba M.,Natlagric Res Center | Chiba M.,Niigata University | Matsumura O.,Natlagric Res Center | Terao T.,Natlagric Res Center | And 2 more authors.
Japanese Journal of Crop Science | Year: 2011

Deep-flood irrigation (DFI) is a method used to suppress the occurrence of chalky grains, which is becoming a serious problem due to global warming. The mechanism of reducing chalky grains by DFI was analyzed with regard to the source ability of stems and leaves that supply carbohydrate to the grains because shortage of carbohydrate flow into the endosperm is considered to be the main cause of chalky grains. DFI increased the amount of nonstructural carbohydrate (NSC) reserved in stems and leaf sheaths at the full heading stage. This result suggests that DFI increased the translocation of carbohydrate reserved in stem and leaves before heading. In addition, DFI increased the amount of nitrogen in leaf blades at the full heading stage as well as leaf area at the ripening stage, which suggests that DFI promotes photosynthesis in the ripening process. In conclusion, DFI increases both the amount of carbohydrate reserved before heading and photosynthetic ability after heading, consequently decreasing the occurrence of chalky grains.

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