Agricultural soil management may affect soil carbon storage. We predict soil carbon storage using the RothC model to determine the effects of cover crop and tillage system. The model used a customized version RothC improved model (Shirato, 2006) adjusted to Andisols. A long-term field experiment has been conducted in progress at the Field Science Center of Ibaraki University since 2002. This experiment combined three cover crop managements (fallow, hairy vetch and rye), three tillage systems (no-till, plowing and rotary) and two N fertilizations (100 kgN/ha for upland rice 20 kgN/ha for soybean, no fertilize) with four replications. Soil samples were collected at each depth (0-2.5, 2.5-7.5, 7.5-15 and 15-30 cm) twice a year. The RothC improved model has been applied to predict soil carbon storage based on the field data. The results of comparison between the actual data and the predictions of soil carbon storage indicate the model’s predictions were acceptable for notill and rotary not for plow system. Input organic matter was increased to incorporate in cover crop treatment. The model prediction suggests that rye cover crop will increase in soil carbon storage, and hairy vetch cover crop will be stable. On the other hands winter fallow will decrease soil carbon because there is very little plant residue incorporation in a year. These results strongly suggest that an appropriate farming system is necessary to maintain or improve soil carbon storage.

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The effect of CPPU (N1-(2-chloro-4-pyridyl)-N3-phenyulurea) application to eleven kiwi fruit varieties (six varieties of Actinidia chinensis, five varieties of A. deliciosa) were investigated. ‘Rainbow Red’ and ‘Kobayashi Sanzyuukyuu-gou’ showed promotion of fruit maturity by CPPU treatment. The treatment was effective in enhancing fruit enlargement in all varieties. Several varieties showed deepening of peel color, depression unevenness of fruits, furrowing of fruits, hypertrophy of the fruit apex, and fruit drop. These findings show great varietal differences in the effect of CPPU treatment. However, differences in effect of treatment between A. chinensis and A. deliciosa remained uncertain. Therefore, it is thought that further examinations remain necessary.

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We investigated the effects of nitrogen fertilization rate and the timing of fertilization on the growth, fruit yield and fruit quality of the short-internode squash cultivar Cucurbita maxima Duchesne ‘TC2A’ based on experiments performed in an Andosol upland field converted from a paddy rice field in Hokkaido, Japan. Rice (Oryza satuva L.) was planted in the previous year and cattle manure composted with wheat straw at a rate of 1 t/10a was applied before ‘TC2A’ seedlings were transplanted in the experimental field. The treatment factor included in this experiment was the amount of nitrogen fertilization : 0, 4, 8 and 12 kg N/10a. Increasing the nitrogen application rate resulted in increases in both fruit yield and quality, but a rate of 12 kg N/10a failed to provide any further improvement over a rate of 8 kg N/10a. Basal fertilization plus topdressing, as compared with basal fertilization alone, enhanced foliage persistence and alleviated the decrease in quality caused by sunburn on the fruit surface and subsequent rotting. These results suggest that 4 kg N/10a basal fertilization plus 4 kg N/10a topdressing would be effective for ‘TC2A’ cultivation in upland fields converted from paddy fields in Hokkaido.

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The present study aimed to develop a technique for raising middle rice seedlings under the pooled condition with organic fertilizer. We set up experimental plots in which rapeseed oil cake containing 1g nitrogen and ground fish containing 1g nitrogen were mixed with forest surface soil to prepare nursery soil. Plots were kept fallow for 0, 1, 2, or 4 weeks. All plots appeared to have satisfactory growth conditions for middle rice seedlings, but irregular seedling growth were observed in the nursery boxes of the 4-week plots.

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We investigated the effect of tedding-less operation during sun drying process on yield, on collection efficiency for the rice straw, and on total cost of bioethanol production. The moisture content of tedding-less straw had fallen to around 20% by drying for 50 days, almost the same as that of tedded straw after rainfall during drying. Tedding accounted for 12% to 27% of the total operation time. In its absence, the cost of straw collection decreased with the yield, while the operation time was linearly increased with the yield. We concluded that the tedding could be omitted during straw drying in area like a tested field, Kanto district, Japan. The tedding-less operation can contribute to the reduction of total cost for the bioethanol production from straw.

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