Red rice (or red-kerneled rice) is a kind of rice containing tannin pigments giving the hulled rice a red or brownish red appearance. Both japonica-type and indica-type red rice have been cultivated in Japan. The japonica red rice is presumed to have been introduced to Japan from the Asian Continent in ancient times along with white rice. Some wooden tablets excavated from court ruins and historical documents show the cultivation of red rice over Japan during the 7th and 8th century. The red rice of indica-type, named ’Taitoumai", was introduced from China during the 14th and 15th century (the Medieval ages). This long grain type of red rice had been cultivated extensively in the central and southwestern part of Japan for its early ripening, drought resistance, insect resistance and high yield though its taste was inferior. It occupied the maximal cultivation area during the 16th and 18th century (the Edo era). Around the later half of the 19th century (the Meiji era) these two types of red rice were gradually eliminated and disappeared finally from the paddy field in Japan. As exceptions, some japonica red rice, which were regarded as sacred, have been cultivated at shrines, while some red rice remained as weedy rice in local areas. The cultivation of japonica red rice revived in many districts in Japan from about 20 years ago. The intensive interest for cold rice has resulted in the emergence of many kinds of secondary products (cold noodles, cakes, alcoholic beverages, etc.) and ultimately in the promotion of regional social activities (educational programs, rice festivals, etc.). In addition, red rice is attracting attention as a functional food because it is rich in polyphenols. This paper summarizes the history of red rice and recent trends in Japan as follows. (1) The definition of cold rice that contains red rice, purple-black rice and green rice, (2) red pigment of red rice, (3) history of cultivation of red rice in Japan, (4) remaining red rice and weedy rice, (5) antioxidative activity of cold rice, and (6) recent cultivation and breeding of red rice in Japan.

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Dry matter production and related characteristics of rice plants cultivated in non-tillage and non-paddling paddy fields (non-tillage plants) were compared with those cultivated in conventionally tilled paddy fields (tillage plants) from 1997 to 1999. The grain yield was not significantly different between the two cultivation methods. However, the yield components were slightly different. In 1997 and 1998 non-tillage plants had fewer spiklets per m² but larger thousand grain weight than conventional tillage plants. In 1999, both the number of spiklets per m² and the percentage of ripened grain tended to be greater in non-tillage plants. The weight of dry matter was lighter in non-tillage plants than in conventional tillage plants until the early ripening stage. This resulted from a lower leaf area index (LAI) in non-tillage plants during this phase of plant growth. In contrast, during the later ripening period, crop growth rate (CGR) was greater in non-tillage plants due to greater net assimilation rate (NAR). As a result, there was no difference in the weight of dry matter between the tillage plants and non-tillage plants. The difference in the NAR may be attributed to the difference in photosynthetic rates during ripening. The higher photosynthetic rate in non-tillage plants was due to the maintenance of high nitrogen levels in leaves.

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To increase the protein content of wheat grain, we applied fertilizer 10 days after heading and examined its effect on agronomic character and flour quality. This top dressing did not affect the agronomic characters except for delaying the mature stage, but increased the 1000-grain weight and test weight. Protein content increased linearly as the amount of applied fertilizer increased, at a rate of about 0.5% per 1gm^-2 nitrogen top dressing. Gluten content increased as the protein content increased, irrespective of cultivars, breeding lines and years. There was a significant correlation between protein content and flour color; as the protein content increased flour color became gray. Nitrogen fertilizing 10 days after heading effectively increased the protein content in wheat.

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To elucidate a suitable fertilizer application method for early sowing of winter type wheat Iwainodaichi, we investigated the effect of late topdressing on growth and grain yield over a 4-year period. Late top dressing decreased the total dry weight at the flowering stage, but did not affect the morphological characters of leaf and stem, leaf area index (LAI) at flowering stage and sink size. The grain yield was increased by late topdressing in 2 of the 4 years as compared with early or standard topdressing. In those 2 years, late topdressing did not affect the number of flts per spike but increased the number of grains per spike and SPAD value during ripening. In the plant with late topdressing, sink size and grain yield were larger in Iwainodaichi than in Chikugoizumi in 3 of the 4 years. This seems to be attributed to the larger potential sink size of Iwainodaichi. These results suggest that in order to get a high grain yield of wheat sown early, large sink size and high SPAD value during ripening are required, and in this respect, late topdressing is advantageous for Iwainodaichi.

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To elucidate the suitable seeding rate for early sowing of winter type wheat Iwainodaichi, the effect of sparse sowing on growth and grain yield was investigated for 2 years. Although the number of shoots, leaf area index (LAI) and total dry weight at maximum tiller stage were smaller in sparse sowing than in standard sowing, LAI, total dry weight and sink size at flowering stage with sparse sowing were not different from those in standard sowing. These results show that sparse sowing did not affect the yield potential at the flowering stage as compared with the standard sowing. Sparse sowing did not affect culm length, the number of internode and the length of each internode, but increased the number of spikelets and flts per spike, leaf length and width, and diameter of internode. During ripening, SPAD value was higher in sparse sowing. The number of spikes per area was smaller in sparse sowing but the number of grains per spike was larger in sparse sowing than those in standard sowing, and thousand grain weight was not different between sparse and standard sowing. As a result, grain yield in sparse sowing was similar to or m than that in standard sowing. Sparse sowing, also, gave high lodging resistance. These results suggest that sparse sowing is superior to standard sowing in early sowing of Iwainodaichi.

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The yield and yield components of soybean, cv. Tamahomare planted at six square densities (15cm × 15cm, 20cm × 20cm, 25cm × 25cm, 30cm × 30cm, 35cm × 35cm, and 40cm × 40cm) were examined in 1999. The dry weight of stems highly correlated with the number of branches (r=0.74^**). The emergence rate and the survival rate of branches decreased as light intensity decreased when the relative intensity at the nodal position was less than about 35% and 10% of daylight, respectively, though they were constant when the light intensity was higher. Consequently, the number of branches and the dry weight of stems per plant decreased, and those per m² increased gradually as planting density increased. The grain yield significantly correlated with the number of pods (r=0.71^**). When the light intensity at each node position on the main axis was less than about 20% of daylight, the podding rate decreased as light intensity decreased, although it was constant when the light intensity was higher than about 20% of daylight. Consequently, podding rate decreased as the planting density increased. Mover, seed number per pod decreased as the planting density increased, although not significantly. These results suggested that the higher the planting density, the lower the pod number per plant due to reduction of branches and low podding rate, and the lower seed number per pod. Thus, the grain yield of soybean was lower when planting density was 15cm × 15cm or 20cm × 20cm than when planted at a density of 25cm × 25cm or 30cm × 30cm.

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The objective of this study is to establish a method of nitrogen fertilization suitable for growth and yield, particularly for dry matter production and nitrogen absorption in summer buckwheat (Fagopylum esculentum Moench, c.v. Kitawasesoba) cultivated in western Japan. Ammonium sulfate was applied as a basal dressing at the nitrogen rate of 0, 2, 4, and 10g/m² in a drained paddy field. Dry weight and nitrogen absorption increased with increasing amount of nitrogen application. Seed yield was increased by nitrogen application up to 4g/m² due to an increase in the number of seeds per plant. In the plot to which 10g/m² nitrogen was applied (10g/m² plot), the harvest index and nitrogen use efficiency of the seeds were low, and seed yield was almost the same as those in the 4g/m² plot. In the 10g/m² plot, the dry matter partitioning rate was still high in the stem during the late ripening period. Slow-release fertilizer (70 days type) as a basal dressing and ammonium sulfate as a topdressing at the flowering period were applied. However, they did not increase seed yield. It is thought that the promotion of initial growth by basal dressing is important for buckwheat cultivation in western Japan because seeds are sown in the spring when temperature is still low. The application of nitrogen fertilizer at the rate of 4g/m² would be necessary even in drained paddy fields.

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In 1998, premature heading was observed in the early season culture field of the extremely early rice cultivar ‘Tosapika’ in Kochi Prefecture. To clarify the factors associated with that, the effect of temperatures (constant temperature:25 and 20°C) under natural daylength around the summer solstice (long day:14.15-14.43 hours) and after the autumn equinox (short day :10.32-11.53 hours) on the differentiation and development of young panicle was examined using the seedlings raised in stock-raising pots (each pot size is 1.5 × 1.5 × 2.5cm) at a rate of one seed per pot. The cumulative temperature from sowing to panicle differentiation was lower in ‘Tosapika’ and its parent, Kouiku No.27 than in the cultivars bred in Hokkaido irrespective of the daylength. The effects of daylength and temperature on the panicle differentiation when examined based on the effective cumulative temperature (ECT, base temp. 10°C) were smaller than that when examined based on the cumulative temperature in each cultivar. In the seedling of ‘Tosapika’ the panicle differentiation and development were scarcely influenced by daylength and the panicle formation stage (average length; 1mm) was observed at 301-348°Cday (ECT) from sowing and at 5.3-5.7 plant age in leaf number on the main culm. It was about 20 days bef heading under 25°C condition. Mover, the ECT after sowing to flag leaf expansion, which is closely related with the earliness of cultivars was also lower in ‘Tosapika’ due to the fewer number of final leaves on the main culm in comparison with the cultivars bred in Hokkaido. From these results, it was concluded that the thermo- and photo-sensitivities and basic vegetative growth of ‘Tosapika’ were comparatively low, and these characteristics were similar to those in its parent, Kouiku No.27.

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The effects of irrigation at the early growth period on the thickening and shape of the tuberous roots in sweet potato were examined. The number and length of the tuberous roots were determined by 70 days after the planting(70 DAP). There was high positive correlation between the length and width of the tuberous roots, which indicated that the rate of lateral growth was higher in the long tuberous roots than in the short ones. The rate was higher in the irrigated plot than in the non-irrigated plot. Width/length ratio of the tuberous roots, which were diversed at the early growth period, tended to converge as the growth progressed. At the final growth period, it was larger in the irrigated plot than in the non-irrigated. The number of spindle-type and long spindle-type tuberous roots occupied 35% and 65%, respectively, of the total number at 70 DAP. At the final growth period, however, most of the tuberous roots were of the spindle-type in the irrigated plot, although many of them were still of the long spindle-type in the non-irrigated plot. These results indicate that the irrigation at the early growth period greatly affects the shape of the tuberous roots.

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We examined the nodal distribution of the numbers of ripened and empty grains and the grain weight in the panicle in 12 rice cultivars with different cold tolerancecultivated in cool water(daily mean temperature, 19C). The number of grains including empty ones did not vary so much with the nodal position on the primary rachis-branches, but was high at the middle part on the secondary rachis-branches. This tendency was stronger in cold tolerant cultivars, and the number of ripened grain at each nodal position on the panicle was also higher in cold-tolerant cultivar. The nodal variation in grain weight was larger on the secondary than on the primary rachis-branches in all cultivars. On the secondary rachis-branches of the cold-tolerant cultivars, the lower the nodal position, the higher the fertility percentage, but the weight of each grain negatively correlated with the fertility percentage, In the cold-tolerant cultivars fertility percentage was higher in the order of lower>middle>upper pa of panicles, and in the order of tertiary>secondary>primary rachis-branches. This tendency was not clear in the cold-susceptible cultivars. Participation of assimilate transport from stems and leaves in the negative correlation between the fertility percentage and gain weight remains to be examined further.

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Rice yield was estimated from that in 30 hills harvested at the center of each paddy field in Kikuchi district Kumamoto Prefecture in 1985. The rice fields surveyed were managed by two groups of innovative farmers who aimed to improve the stagnant grain yield of 5t/ha. Grain yields at 50 spots in 43 paddy fields varied from 7.44t/ha to 5.54 t/ha and the difference was not related to planting density, number of panicles per unit land area, grain-straw ratio, and 1000 grain weight, but related to grain yield per panicle. The grain yield level was associated with the maximum number of stems per unit area and the percentage of fruit bearing stems. The relations among yield level, the maximum number of stems per unit area and the percentage of fruitful stems were denoted as follows:580 panicles/m²→80%→6.6t/ha, 580 panicles/m²→70%→6.3t/ha, 480 panicles/m²→80%→5.7t/ha. The relationship between the increased stem number from 16 to 23 July and grain yield irrespective of soil texture, the kinds of winter crops, and fertilizer. The relations were denoted as follows : 230 panicles/m²→6.6t/ha, 200 panicles/m²→6.3t/ha, 160 panicles/m²→5.4t/ha.

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