Paddy rice seedlings transplanted at different growth stages in Miyagi prefecture in 2003 were examined for heading date and the percentage of ripening on all stems in each hill in relation to cool summer damage. In that year, the low temperature and insufficient sunshine continued from June for a long period, and floral sterility due to the low temperature occurred frequently. The heading date was earliest in the plants transplanted at the middle-seedling stage (MS plants) followed by those transplanted at the young-seedling stage (YS plants), and those transplanted at the nursling-seedling stage (NS plants), in this order. The heading period was longer than that in normal years, and was 11, 13 and 9 days in the MS, YS and NS plants, respectively. The difference in the 50% heading dates between the MS and YS plants was 4.7 days, and that between the YS and NS plants was 4.2 days. Irrespective of the growth stage of the seedlings at transplanting, the later the heading date within the period from August 10 to August 20, the higher the percentage of ripening on the stem. The percentage of ripening on the stems headed after August 20 was nearly the same. Weight of brown rice per unit area was lower in the MS plants and this was attributed to the sterility caused by the low temperature. We conclude that the damage caused by floral sterility from low temperatures can be mitigated by these seedling types.

View full abstract

The effect of shooting a slow-release fertilizer with the seed and draining after submerged direct seeding on the establishment of rice seedlings were investigated in pots and containers using a “shooting hill-seeder.” In the pots (containers) seeded with fertilizer, the early growth of the aerial part and the subterranean part were slower than in the pots (containers) with fertilizer incorporated into the plowed layer. The soil with the fertilizer shot had a higher ammonium nitrogen content than the soil with fertilizer incorporated into the plowed layer. Seedling emergence and establishment were improved in the pots with the fertilizer shot that had been draining the flooded water after seeding of rice, and the early growth of the aerial part and the subterranean part were also promoted by the draining compared with that in flooded pots. These results suggest that the delay of the early growth by simultaneous shooting of fertilizer with seed was reduced by draining.

View full abstract

In Hokuriku area, the field converted from heavy clay paddy is often wet, but most of soybean is cultivated in such fields. Soybean differentiates flower buds in the rainy season, which is from late June to mid July, and is susceptible to wet conditions in this period. Soybean (Glycine max Merr. cv. Enrei) was cultivated in the field at the initial stage of conversion from heavy clay paddy, and the effects of the wet condition and application of coated urea were investigated. Field experiments were conducted in control and wet field. The wet field (6m width field) was ditched peripherally, and the ditch stored water in the rainy season. Five types of coated urea were broadcasted at a late of 10gN/m² before rotary tillage. The types of coated urea were 4 parabola types (40-day, 70-day, 100-day and 140-day types), and 1 sigmoid type (100-day-S). The 40-day, 70-day and 100-day types dissolved a lot of nitrogen in the rainy season. Yield and nitrogen content decreased in the wet field. Yield decreased due to the decrease of pod number, and nitrogen content decreased due to the decrease of the amount of ureide-N which is mainly derived from N₂ fixation. In some cases, application of coated urea abated these wet injuries, and the effect of the 40-day, 70-day or 100-day types was remarkable. The 40-day and 100-day types increased the yield, and the 70-day type increased the amount of ureide-N. It is suggested that the nitrogen dissolved during the rainy season abated the wet injury of soybean.

View full abstract

To establish the cultivation techniques that prevent the occurrence of seed-coat cracking (SCC) in soybean cultivar ‘Sachiyutaka’ we investigated the effects of seading time and planting density on the occurrence of SCC in ‘Sachiyutaka’ The occurrence of SCC tended to increase as the sowing time was advanced; it was increased by sowing in June and decreased by sowing later than July 10. The occurrence of SCC was decreased by increasing the planting density. However, in late sowing on July 24, no significant difference in the occurrence of SCC was observed between the sparse and the dense planting. The occurrence of SCC negatively correlated with grain number per m² and seed-stem ratio, but was not correlated with 100-grain weight and yield. We recommend to delay the sowing time and increase planting density to increase the seed-stem ratio and to keep a sufficient number of grains per m² as a measure to prevent the occurrence of SCC in ‘Sachiyutaka’

View full abstract

Total nitrogen and total carbon contents of the soil and the leaf yield in a long-term unfertilized mulberry field (NF) were compared with those in a chemically fertilized field (F) for 19 years from 1985 to 2003. Each year, 30, 20 and 20g m^-2 of nitrogen, phosphorus and potassium, respectively, were applied to the F field; a half in spring and the remaining half in summer. Weeds and litter fall were all removed from both F and NF fields. Originally, the mulberry cultivar Kairyonezumigaeshi had been grown in both fields for more than 25 years. In the spring of 1991 (the 7th year of the experiment), mulberry (cv. Ichinose) was replanted to both fields. The mulberry leaves were harvested twice a year in spring and in late-autumn, by cutting and leaf plucking methods, respectively. Total soil nitrogen and carbon contents of the soil in the NF field reached equilibrium after 15 years of treatment, and the yearly yield of fresh leaves from NF was stable at 1800 to 2000g m^-2 for 5 years after replanting. The changes in nitrogen content of the plant and that of soil nitrogen suggested 17.5g m^-2 of nitrogen was annually input to the NF field from the natural environment. The source of nitrogen input remains unknown, but a major part of nitrogen was supposed to come from the nitrogen pool in the subsoil layers, from adjacent environment and/or through atmospheric nitrogen fixation. In the spring rearing season, during which the time interval between successive harvesting was long and fertilizer application was less effective, the leaf yield was higher in the NF field than in the F field. On the other hand, in the late-autumn rearing season, during which intervals between successive harvesting was short and applied fertilizer was effective, the leaf yield was higher in the F field than in the NF field. The rate of nitrogen content allocation to leaf blades was higher in the NF than in the F field, even though the nitrogen content of the whole plant was lower in the NF field. The characteristic nutrient distribution pattern in the plant may also be a reason for the higher leaf yield in the unfertilized field.

View full abstract

In order to evaluate the usefulness of several physicochemical properties for selecting rice cultivars with high palatability, we analyzed the relationship between the palatability and the physicochemical properties using 20 japonica rice cultivars from 1998 to 2002. By cluster analysis the 20 cultivars were classified into four groups besed on their palatability score for five years. We examined the relationship between the palatability score and physicochemical properties of the mixture of all four groups. The amylose content, protein content, maximum viscosity, breakdown, and textural characteristics (H/—H : hardness / adhesion ratio, H/A₃ : hardness / adhesiveness ratio), showed a significant correlation with palatability score. We examined the palatability score of rice strains that were recently developed in Fukuoka Agricultural Research Center, and found that the number of the cultivars with extremely lower palatability than Koshihikari (group 4), has been decreasing year by year. Then, we analyzed the relationship between the palatability score and physicochemical properties of the mixture of group 1, 2 and 3, which showed a relatively higher palatability than group 4. Only amylose content and textural characteristics (H/—H, H/A₃) showed a significant correlation with the palatability. We compared the amylose content and textural characteristics among the four groups. The difference in amylose content among these three groups were not significant. However, a significant difference of H/—H was detected between group 2, which has better palatability than Koshihikari, and group 3, which has slightly lower palatability than Koshihikari. Therefore, textural characteristics could serve as useful index traits for developing rice cultivars with extremely high palatability in the breeding programs.

View full abstract

Steamed and dried sweet potato slices called “Hoshi-imo”, is an important agricultural product in Ibaraki prefecture in Japan. In recent years, a large amount of Hoshi-imo is imported, and improvement of the quality of domestic Hoshi-imo is critical to survive competition. Here, we investigated the changes in quality factors such as toughness and brix of Hoshi-imo during the drying process to improve the processing technique and to breed high-quality lines. The luminosity and yellowness of steamed slices decreased and became reddish as they dried. The color characteristics of the slice just after steaming distinctively differed among lines, and the difference was evident even after drying though the difference in luminosity decreased with time. The toughness and brix of Hoshi-imo differed among lines throughout the drying process. These results indicate that it is possible to predict market quality of Hoshi-imo just after the steaming process and to select breeding lines without drying. The moisture content of Hoshi-imo fell to below 30 % after drying in all the lines tested. The term of drying should be shortened in some lines because they become too tough during the drying process. A negative correlation existed between toughness and brix of Hoshi-imo among the lines and cultivars of sweet potato studied, suggesting that temperature should be gradually raised in the steaming process to promote saccharification and to obtain high quality products.

View full abstract

Influences of autumn skiffing level on inner-space circumstances, production and quality of tea (Cultivar.‘Yabukita’) and harvesting rate by mechanical plucking were investigated from October, 1999 to September, 2000 at Makurazaki, Kagoshima, Japan. By introduction of mechanical plucking, unharvest rate of fresh tea leaves reached to 34-37%. Shallow autumn skiffing formed a thick leaf layer, high leaf area index (LAI) and high light-interception, predicting high yield in the next year. The shallow skiffing induced bud growth during winter, lower percentage of banjhi shoots to the total, higher quality of tea in the 1st crop and higher tea yield in the 3rd and 4th crop. The shallow and medium skiffing treatment resulted in higher plucking yield through a year and high tea quality.

View full abstract

The difference (ΔT) between canopy temperature (T_c) and air temperature (T_a) was examined for its validity as a criterion for drought avoidance in upland rice under field conditions in Japan, where vapor pressure deficit is low. The varieties which were assumed to differ greatly in drought avoidance mainly because of the difference in root depth, were grown in fully irrigated field plots (FIFP) and non-irrigated field plots (NIFP) in 2001, and in NIFP in 2002, under a rain shelter. On six dates during one month until heading in each year, T_c, T_a and stomatal conductance (g_s) were measured nearly simultaneously using infrared thermography, thermometer and porometer, respectively. Root depth was measured at the harvest in 2002. In 2001, the rank order of ΔT averaged for all the dates (the cooler the higher) corresponded to that of g_s (the higher the higher) among varieties within the same irrigation scheme. However, the rank order of ΔT and g_s in FIFP did not correspond to that in NIFP which represents the degree of drought avoidance. In 2002, ΔT on each of the dates and the average for all the dates differed significantly among varieties. The deeper the roots, the higher the g_s and the lower the ΔT. These results indicate that ΔT in NIFP can be utilized as a criterion for drought avoidance in upland rice under field conditions in Japan.

View full abstract

The factors that decrease the kernel weight of Hokkaido wheat cultivar “Haruyutaka” in Western Japan were analyzed based on the kernel weight of F₁ of the cross with Kyushu cultivar “Daichinominori.” The F₁ kernels were obtained by a reciprocal cross between these two cultivars in 2000/2001, 2001/2002 and 2002/2003. The average and variance of the F₁ kernel weight were compared with those of the self-pollinating kernels. The F₁ kernel ripened on Haruyutaka had almost the same weight as that of the self-pollinated kernel of Haruyutaka in both average value and variance in all three seasons. The F₁ kernel ripened on Daichinominori plant had heavier average weights than the self-pollinated Haruyutaka kernels in 2001/2002 and 2002/2003, although not in 2000/2001. These results suggested that the source capacity in Daichinominori is higher than that in Haruyutaka, but it may vary with the season. In addition, it is thought that Haruyutaka has dominant kernel weight-decreasing genes.

View full abstract

Typhoon 0415 (T0415, MEGI) passed through the Sea of Japan coast of Hokuriku and Tohoku Districts on August 19-20, 2004. A gust of wind stronger than 30m/s was recorded in the coastal region, and a gust of wind at 38.3 m/s, 39.6 m/s, and 41.1 m/s was observed in Aikawa, Sakata, and Akita, respectively. However, there was little rainfall before and after the passage of the typhoon. Consequently, the adhering salt entered the rice plant, and salty wind damage occurred by drying up the cells. Near the seashore, 2.7-3.2mg salt had adhered to the panicle, and the amount of salt adhesion per panicle (mg/panicle) negatively correlated with the distance from the seashore. The total amount of the agricultural damage by T0415 was 18 billion yen, 10,200 million yen, and 7,200 million yen in Akita Prefecture, Yamagata Prefecture, and Niigata Prefecture, respectively. The amount of rice damage occupied three fourths of the whole crop. The ratio to normal year of the rice yield fell greatly in Akita Prefecture (Kisakata cho, southern prefecture coast area) and Niigata Prefecture (Sado city). In the Niigata Sado area and the Akita Honjo area, the quality of rice deteriorated remarkably.

View full abstract

We examined a special fertilizer for non-split application to paddy rice in order to develop a labour-saving method of feritlizer application suitable for climate, soil condition, and cultivation system in Tomo area of Gunma prefecture. We used seven kinds of coated urea which varied in release type and period, and examined the optimum release type, release period and combination or mixing-rate of fertilizers. Experiments over five years showed that the experimental fertilizers composed of (LP70+LPS80 or LP100+LPS100 with the ratio of fast and slow-release feritilizer at 1:1) was as good as the standard fertilization system which were both of basal and top dressing in yield and quality. From these results, we consulted with the local fertilizer company and determined that the special fertilizer should consist of LP70 (fast-release fertilizer) and LPS80 (slow-releace fertilizer) at a ratio of 1:1. In 2000, we started selling the special fertilizer named “Fureai- Ippatsu-shouryokugata 253”, and it is widely used today.

View full abstract

α-Amylase activation in wheat grain lowers amylograph viscosity and it is influenced by weather conditions, mainly rainfall, and pre-harvest sprouting. To predict the time of α-amylase activation in a wheat variety Hokusin, we investigated the effects of weather conditions on the levels of grain dormancy. The grain dormancy at the maturing stage showed a negative correlation with rainfall and temperature during the week before the maturing stage. After the maturing stage, levels of dormancy declined over time and were decreased by rainfall especially by continuous rainy days. The effect of pre-harvest rainfall was greater at a lower temperature; 15°C followed by 20 and 25°C in this order. According to these results, we developed a program operated on a personal computer, to predict for time of α-amylase activation. In this program, levels of dormancy after the maturing stage were estimated by mean temperature, rainfall, sunshine hours and mean humidity for 7 days before the maturing stage. Accuracy of the prediction was higher than 95% in wheat sampled at the farmers’ field. Most wheat grains with high levels of dormancy showed relatively high amylograph viscosity, while wheat samples with low dormancy often showed low viscosity. In conclusion this program could be useful to determine the optimal harvest time.

View full abstract

[in Japanese]

View full abstract