The aging and decrease of farmers, the enlargement of management scale and the diversification of rice usage are predicted in Japanese rice cultivation. Branded rice varieties with weak lodging resistance have been cultivated under low fertilization in conventional rice cultivation, to produce low yield but high price rice having good eating quality for household consumption. In contrast, it is effective to cultivate the high yield varieties with strong lodging resistance under high fertilization, to produce low price but high yield rice for business use and feed. The cool climate in the Tohoku region is suitable for producing high yield rice with good appearance and eating quality. By contrast, it reduces the variation of cultivation systems and increases the risk of cool weather damage and blast. In the large scale - agricultural management in the Tohoku region, direct seeding, sparse planting and late transplanting of commercial rice and feed rice is promising since they can be co-planted with the cultivation of branded rice. Thus, we discussed the future direction of breeding and cultivation techniques of rice for business use and feed in the Tohoku region.
The optimum sowing time and planting density of soybean cultivar; “Satonohohoemi”, in South Kanto were clarified and the growth and yield of “Satonohohoemi” were compared with those of other soybean cultivars cultivated in East Japan. The yield and protein content of seeds sown in July were not lower than those sown in June, due to increased number of seeds per pod, and increased number of pods per node in July sowing. In July sowing, the yield and protein content of seeds in the plants cultivated at 22.2 plants per m2 were not significantly different from those cultivated at 11.1 plants per m2. The stem senescence was scarcely delayed in July sowing in 2016 but it was delayed in many plants in 2017. In conclusion, soybean cultivar “Satonohohoemi” should be sown in July and cultivated at 11.1 plants per m2 in South Kanto. In “Satonohohoemi”, the stem diameter was larger and the lowest stem node with pods was higher than those in “Enrei”, “Tachinagaha” and “Ayakogane”. The yield and protein content in seeds in “Satonohohoemi” were equal to or higher than those in the other soybean cultivars. Thus, soybean cultivar “Satonohohoemi”, can be cultivated in South Kanto.
The food–service industry demands inexpensive but palatable rice. The rice cultivar “Koisomeshi” was bred for high yield and good palatability to satisfy this demand. To obtain the suitable nitrogen fertilization regime for “Koisomeshi”, we examined the effects of nine treatments, combining three nitrogen levels at the early stage of rice growth (3, 6, and 9 g m–2) and three nitrogen levels applied as top dressing at the panicle formation stage (0, 3, and 6 g m–2) on the yield and appearance quality of grains for over three growth seasons. Grain yield was high under 3 or 6 g N m–2 top dressing, which was attributed to the increase in spikelet number per area. Appearance quality of grains decreased with increasing nitrogen application, especially in top dressing. Based on these results, we concluded that the nitrogen applications at 6 g m–2 at the early growth stage and 3 g m–2 at the panicle formation stage were the most suitable for “Koisomeshi”. In addition, an appropriate transplanting date should be selected to achieve good appearance quality of grains because appearance quality varied greatly with the weather conditions during the ripening period.
Cultivation of paddy rice on rock wool molding medium is useful for reducing the weight of soil molding and saving labor. The growth characteristics of paddy rice seedlings cultivated using the new standard 13 mm thick rock wool molding medium (molding medium) and the conventional 16 mm molding medium were examined using the controlled fertilizer, i.e., NAEBAKOMAKASE. There was no significant difference between the following characteristics of paddy rice seedlings cultivated in the two molding media: height of plants, number of roots (total number of seminary root and crown root), dry weight of above-ground and underground parts, and the strength of seedling mats. It was estimated that 877-1111 g of fertilizer per nursery box was needed to secure proper soil covering (5–7 mm) applying the NAEBAKOMAKASE fertilizer to the 13 mm molding medium. Therefore, the 13 mm molding medium is expected to be 1.2–1.5 times more effective than the 16 mm molding medium.
The sweet potato (Ipomoea batatas (L.) Lam.) cultivar “Kenroku” has been cultivated mainly to produce steamed and dried slices. Therefore, it is necessary to improve both the size and the appearance of the storage roots. In sandy loam fields, fertilization before transplanting of cuttings significantly increased the number of storage roots, but significantly decreased the average weight of each storage root; as a result, total yield was comparable to that of cuttings grown without fertilization. In contrast, delayed fertilization at 8 weeks after transplanting significantly increased the average weight and total yield of the storage roots, although the number of storage roots decreased. In addition, the corrugations that are frequently observed on the surface of storage roots grown without fertilization were decreased by the delayed fertilization. Different fertilizer application methods did not affect the contents of sugars and β-carotene. These results strongly suggest that delayed fertilization can improve the production and quality of storage roots of “Kenroku” sweet potato.
We investigated the annual variation of the grain shattering degree in rice by the grasping method using four rice cultivars cultivated in Okayama prefecture; “Hinohikari” with a hard shattering habit, “Omachi” with a slightly easy shattering habit, “Akebono” with an easy shattering habit, and “Asahi” with a very easy shattering habit. The field experiments were conducted in a high temperature year, 2010 and a low temperature year, 2015. The shedding rate estimated by the grasping method hardly varied with the year in “Hinohikari” and “Omachi”. However, it was higher in 2015 than in 2010 in “Akebono” and “Asahi”, and the annual variation was larger in “Asahi” than in “Akebono”. These results suggest that the shedding rate fluctuates with the year largely in cultivars with an easier shattering habit and that it is increased by a low temperature.
Numbers of basal branches (BB) and inflorescence branches (IB), which vary with planting density, are the important seed yield components of flax (Linum usitatissimum L.). The effects of planting densiy on the development of BB and IB of oilseed and fiber flax cultivars were studied. Seeds of “Lirina” and “NR2” (oilseed-type) and “Aoyagi” and “Pernau 1” (fiber-type) were drill-sown with row spacing of 30 cm in 2017 and 2018. After emergence, plants were thinned to 1 cm spacing (high planting density) and 5 cm spacing (low planting density) within a row. The oilseed cultivars were shorter, had a longer inflorescence compared with the total length, and produced more capsules and seeds than the fiber cultivars. All cultivars had capsule-bearing BB at a low planting density. “Lirina” had fewer capsule-bearing BB than other cultivars. Compared with the oilseed cultivars, “Aoyagi” had fewer IB on the main stem but “Pernau 1” did not. In all the cultivars, both the number of IB on the main stem and the number of capsules per IB were higher at a low planting density than at a high planting density. The increase in the number of capsules per IB, which was partly caused by the development of secondary inflorescence branches, was more conspicuous in the oilseed cultivars than in the fiber cultivars.