The anaerobic digestion of livestock manure is an environmentally compatible technology used for the production of renewable energy. Anaerobically digested residual slurry has been used worldwide as a liquid fertilizer in both upland and paddy fields. However, a controversial question remains as to whether the application of slurry to rice paddy fields increases methane emissions; although methane is one of the most prevalent greenhouse gases, little is known about the effects of the long-term application of residual slurry on methane emission. In this study, we repeatedly applied slurry to a paddy field for six years at different application rates (10, 15, and 20 g N m−2 based on ammonium-nitrogen content). At the fifth and sixth years of application, we evaluated the effect in terms of methane flux and soil total carbon content. The effect of the long-term application of the slurry (10 g N m−2) on grain yield was equivalent to that of chemical fertilizer (10 g N m−2). The application of the residual slurry was likely to increase the cumulative methane emissions during rice growing season in both 2006 and 2007. On the other hand, we observed that soil total carbon did not accumulate significantly in the soil. Thus, we cannot rule out the potential risk of additional methane emissions caused by the application of the residuary slurry to paddy fields.

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Predicted climate changes, in particular, the increased dimension and frequency of heat waves, are expected to affect crop growth in the future seriously. Hybrid rice relies on seed production from male sterile and restorer lines. Experiments were conducted over two consecutive years to compare the high temperature tolerance of parents of different hybrid rice combinations, in terms of fertility rate, flowering pattern, pollination and physiological parameters of the lodicule. Three male sterile lines and a broad compatibility restorer line (as pollen donor and conventional variety as well) were grown to heading stage and then treated with average daily temperatures of 26°C (range 23–30°C), 28°C (25–32°C), and 30°C (26–34°C), respectively, continued for 5–7 days each in a natural light phytotron which simulated the local typical high temperature weather in the field. The results indicated that male sterile lines were more sensitive to high temperature than the restorer line for fertility rate, and the sensitivity varied between varieties. The fertility rate of the restorer line was maintained at about 90% under the high temperature treatments, while it decreased in the male sterile lines by 23.3 and 48.1% at 28 and 30°C, respectively. The fertility rate of the most sensitive line declined by 70%, and the tolerant line declined by 34% at 30°C. Glume closure in the male sterile lines was a major reason for the reduced fertility rate under high temperature, which is closely correlated with carbohydrates content and the vascular bundle pattern in the lodicule. The present study identified a useful trait to select male sterile lines with high temperature tolerance for seed production.

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We analyzed the heredity of anther morphology in rice (Oryza sativa L.) using incomplete diallel crosses of six japonica restorer lines and eight cytoplasmic male-sterile (CMS) lines, and 48 F1 combinations resulting from these crosses. We analyzed four traits: the length of dehiscence formed in the apical (ADL) and basal (BDL) parts of the anther and the respective widths, ADW and BDW. The ratios of Vgca (variance of general combining ability) to Vsca (variance of specific combining ability) were 8.0 for BDL, 1.4 for BDW, 3.0 for ADL, and 2.8 for ADW. Narrow-sense heritability (HN2) was 76.5 % for BDL, 37.9 % for BDW, 66.0 % for ADL, and 65.9 % for ADW. The effects of GCA (general combination ability) for BDL ranged from −67.0 to 68.9 μm (CMS lines) and from −33.4 to 43.0 μm (restorer lines); those for ADL were −46.7 to 44.0 μm (CMS lines) and −29.5 to 34.0 μm (restorer lines). We conclude that BDL and ADL have high heritability, and we can modify the size of apical and basal dehiscence by selecting suitable CMS and restorer lines.

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