To establish the cultivation techniques of early-winter direct-sowing of rice in the Hokuriku region, we evaluated the effects of cultivar, seed production year and seed coating on emergence rate after wintering and yield by mechanical sowing. Five of the six varieties excluding ‘Hokuriku 193’ commonly cultivated in this region were considered to be practical for early-winter direct-sowing cultivation because the emergence rate after wintering by hand sowing was 34 - 68%. We clarified that the emergence rate of seeds produced in the previous year tended to be inferior to that in the current year, and that seed coating with thiuram improved the emergence rate. An early-maturing cultivar ‘Tsukiakari’ which can be harvested early from the viewpoint of preparing the seeds of the current year, was subjected to a mechanical sowing experiment. The seedling establishment rate in simultaneous plowing and sowing was considered to be approximately 25%. As a result, it was estimated that about 11 kg 10 a^-1 of seeds produced in the current year would be required for sufficient seedling establishment and yield in this cultivation. Brown rice yield of over 500 kg 10 a^-1 was demonstrated through three seasons using ‘Tsukiakari’with the controlled-efficiency nitrogen fertilizers applied to the soil at the time of seeding. This is the first report of early-winter direct-sowing cultivation in the Hokuriku region, and provide basic knowledge for systematically establishing this technology.

In the Tokachi region, peanuts are customarily grown at a density of 5-6 plants m^–2, However the optimal planting density remains to be determined. This study examined the optimal planting density of peanut in the Tokachi region by comparing the growth and yield of the early variety ‘Tachimasari’ grown at the experimental field of Obihiro University in 2021 and 2022 at the planting densities of 5.8 plants m^–2 (5.8-plot), 8.7 plants m^–2 (8.7-plot), and 11.6 plants m^–2 (11.6-plot). Plants in the 5.8-plot grew larger and produced more fertile pods than those in the 8.7-plot and 11.6-plot. On the other hand, pod fertility was higher in the 8.7-plot and 11.6-plot than in the 5.8-plot, and the plants in the 5.8-plot produced many immature pods. Seed yield in the 8.7-plot and 11.6-plot was 254 g m^–2 and 264 g m^–2, respectively, which was significantly higher than the yield of 168 g m^–2 in the 5.8-plot. By growing peanut at a higher planting density than 5.8 plants m^–2, decline of the pod production by each plant could be compensated by the number of plants, resulting in a higher seed yield. Stands in the 11.6-plot appeared to overgrow and exhibited a higher leaf area index than those in the 8.7-plot. This resulted in an increase the incidence of diseases conspicuously in the 11.6-plot. It was concluded that 8.7 plants m^–2 was the optimal planting density for the peanut variety ‘Tachimasari’ in the Tokachi region.

Labor-productivity is a major problem in the hilly and semi-mountainous areas in Southwestern Japan, due to small and dispersed paddy fields. Recently, narrow row and dense planting with selective post-emergence herbicide is being used to reduce labor. The combination of narrow row and dense planting with the new black soybean cultivar ‘Kuroshofuku’, suitable for mechanical harvest, can be a solution for labor-saving production in hilly and semi-mountainous areas. The objective of this study is to compare the agronomic characteristics of ‘Kuroshofuku’ with those of ‘Sachiyutaka A1 gou’, one of the leading cultivars in Southwestern Japan, and to consider narrow row and dense planting. The field experiment was conducted in 2021 and 2022, at two sowing dates and three planting densities at Western Region Agricultural Research Center, Fukuyama. In addition, ‘Kuroshofuku’ was grown in a farmer’s field in a hilly and semi-mountainous area. ‘Kuroshofuku’ showed higher lodging tolerance than ‘Sachiyutaka A1 gou’ in late sowing at the research center. Though significant year × cultivar interaction was observed in normal sowing, the difference in yield between the two cultivars was not significant in late sowing. In the farmer’s field, ‘Kuroshofuku’ reached maturity normally in both two years. In 2022, ‘Kuroshofuku’ showed a higher yield when the entire field was harvested than ‘Sachiyutaka’. These results showed that ‘Kuroshofuku’ can be grown by narrow row and dense planting in late sowing, which will contribute to labor-saving production in Southwestern Japan.

To clarify the challenges of rice seed production after abolishment of the Main Crop Seeds Act, we surveyed the offices of the 46 provincial governments and seed producing farmers in 5 selected prefectures in Japan from 2018 to 2021, including the profitability and labor inputs, which have not been widely available to the general public. Among the farmers in Ibaraki and Saitama prefectures, the seed rice producers had about 1600～1900 yen higher income per work hour than the food rice producers. In Hokkaido with its large-scale management (12.6 ha of average producing area) the work hours were shortest and the gross revenue was the highest, which led to a higher self-evaluation of technologies and overall managemental merit. Among the 44 seed farmers in Toyama, where the work hours per area was longest, a larger seed producing area tended to lead to higher labor productivity and higher self-evaluation of overall managemental merit. With the gradual increase in planting of rice varieties from private companies, several prefectures are encouraging public-private partnership. Human resource development, renewal of old facilities, and a more efficient production system have been identified as most important for building the foundation for seed production and for general seed production. Many prefectures produced many varieties for uses other than staple food (e.g., 62 varieties for sake liquor), which would lead to longer work hours for seed production. This research highlighted the importance of improving labor productivity in seed production.

We developed a yield prediction model of bread wheat cultivar ’Setokirara’ and verified whether the grain protein content could be controlled by variable rate fertilization according to the predicted yield. In the first and second years, six plots with different fertilization rates were established. The vegetation indices normalized difference vegetation index (NDVI) and green NDVI (GNDVI), panicle numbers and SPAD values were obtained at the full heading stage, and yield was determined at maturity. Using two years of data, we obtained a regression line of yield for each vegetation index. In the third year, wheat was sown in late November (standard sowing) and mid-December (late sowing). The amount of nitrogen top-dressing was calculated from the predicted yield using an existing model and applied at the flowering stage. Regarding the yield prediction model, GNDVI had a higher coefficient of determination than NDVI and a significant correlation with panicle number and SPAD value. The regression line of yield by GNDVI was adopted as a yield prediction model because of its high prediction accuracy. In the variable fertilizer application test, the grain protein content was almost the same as the target value for the standard sowing, but greatly exceeded the target value for late sowing. The reason for this error was considered to be the higher grain protein content due to high temperatures after the heading stage. In conclusion, variable rate fertilization is effective in the timely sown ‘Setokirara’, but the model needs to be improved for late sowing.