A study was conducted to develop a simple priming method to improve seedling emergence of okra seeds in non-high-temperature seasons using a seeding mixture as a moisture-conditioning agent. ‘Tokyo Gokaku’ seeds were primed in bottles at 15 to 30°C for 1 to 4 days with seeding mixtures having moisture contents ranging from 35 to 55%. After treatment, seeds were sown in containers at 20°C. Seedling emergence was markedly promoted under the conditions of 30°C/1d/45% moisture: the percentage emergence at 8 days after sowing was 94%, whereas emergence was 53% in the non-treated control. The seeds sown directly in the field in May after priming (30°C/1d/45% moisture) emerged earlier and grew into seedlings with a more uniform top fresh weight compared with the non-treated seeds. The seeds kept at room temperature for several days after priming (30°C/1d/45% moisture) and sown in the field in May showed no differences in emergence compared with seeds sown just after priming. Priming in this study improved emergence, and the effects were maintained even in seeds that were temporarily stored after treatment to simulate postponed sowing.
To utilize the irrigation function of Farm-Oriented Enhancing Aquatic System (FOEAS) in an upland field converted from a paddy field, we examined the effect of sub-irrigation at different growth stages of broccoli and levels of precipitation. Summer-sown fall-harvest broccoli was transplanted in a large pot of andosol or gray lowland soil under rain shelter. The level of feed-water in a connected tank was automatically maintained at –30 cm from the soil surface. Plants were irrigated in each cultivation period (Early, Middle, Late, and Whole periods) under low-level precipitation (25% of monthly average amount of precipitation). By comparing with plants supplied with 25% of the monthly average amount of precipitation, soil water suction in sub-irrigated plots remained low, and plants grew larger. In the Middle and Whole plots, plants had a roughly equal head weight to those in the 100% precipitation plot. The interruption of irrigation at three weeks before harvest improved the preservation of broccoli florets. The effects of sub-irrigation were dependent on the levels of precipitation, and sub-irrigation with 100% precipitation decreased the head weight and shortened the shelf life. The results indicate that sub-irrigation according to the growth stage of plants and rainfall may prevent drought and increase the yield and quality of broccoli.
The sediment of suspended solids (SS), which is derived from the hydroponic gutter after the cultivation of water spinach (Ipomoea aquatica Forssk.) using eutrophic water from Lake Tega, was granulated as granular medium (SS medium). The characteristics of this SS medium and its applicability to vegetable cultivation were studied. The freshly granulated SS medium contained lower NO3-N, but higher exchangeable Mn than commercial soil medium. However, after aerobic fermentation under 30°C, the NO3-N content, exchangeable Mn, and water-soluble Mn in SS medium were markedly increased, with a decreased water content. The early growth of spinach mustard (Brassica rapa L. Perviridis Group) was suppressed using the fermented (30°C) medium, possibly due to the excessive Mn. The Mn content in mixed SS medium with bark compost (SS + bark) were also measured in the present study. The results show that the exchangeable and water-soluble Mn content was significantly decreased by mixing of SS medium and bark compost under 30°C fermentation. Moreover, the Mn content in both the SS medium and SS + bark medium was even decreased under 45°C fermentation treatment with a value of less than 30 mg・kg–1, regardless of the water content of the medium. Although the growth of spinach mustard on the fermented SS + bark medium was lower than that on commercial soil medium, aerobic fermentation improved the chemical properties of SS + bark medium, and SS sediment was considered to show potential for use as growing medium by mixing with bark compost.
We developed a method to select summer-to-autumn-flowering small-flowered chrysanthemum cultivars suitable for the fine control of flowering using light culture. Budding under non-inductive night-break conditions was investigated from March to May. ‘Subaru’ and ‘Sei-chigusa’ showed no budding under night-break conditions during experimental periods. However, ‘Sei-shimanami’ showed a seasonal change in budding under night-break conditions, being late in March and very early in May. This indicated that premature budding under night-break conditions may occur more in late summer to autumn than in early summer. Therefore, we selected summer-to-autumn-flowering small-flowered chrysanthemum cultivars whose flower initiation is inhibited by night-break until cropping on the day of the autumn equinox in September in Okayama Prefecture. Several cultivars that showed later budding than the summer-to-autumn-flowering standard-type chrysanthemum cultivar ‘Sei-un’ used in light culture were selected for the fine control of flowering using light culture. We confirmed and evaluated the utility of these selected cultivars for flowering control using light culture in Fukushima, Akita and Ibaraki Prefectures. Although the flowering time of the selected cultivars varied among prefectures under natural daylength conditions, fine control of the flowering time was established using light culture. These results show that the method developed in this study is useful for selecting summer-to-autumn-flowering small-flowered chrysanthemum cultivars suitable for the fine control of flowering by using light culture.
For simultaneous mechanical harvesting of small-flowered spray-type chrysanthemum, the effects of planting systems on flowering period uniformity were studied using the summer-autumn-flowering-type cultivar ‘Okinamaru’. The influence on flowering periods of the planting position in the plant population, which were made up of six rows and seven columns, and the branching node number after pinching were investigated. Flowering periods in the edge rows facing north or south furrows were shorter than in the inner four rows. The difference in the photosynthetic photon flux density of the plant community at the canopy height from about 15 cm below the canopy was smaller for the inner rows than for the edge rows. These results demonstrate that more solar radiation reached the lower leaves of the inner rows. In the three shoots remaining after pinching, shoots from the lower lateral node showed a longer flowering period, but no significant difference was noted between those of upper shoots and middle shoots. In the next three experiments, changing the center inter-row distance, shading around the plant population and pinching were examined to improve the uniformity of flowering. In the first experiment, using the plant population planted north to south in four rows, the center inter-row distance was changed from 15 to 90 cm. Flowering periods of the inner and outer two rows were respectively measured. The difference in flowering periods between those of the inner and outer two rows decreased as the center inter-row distance increased. This was not significant for a more than 75 cm spacing. In the second experiment, shading materials with a 31% shading rate were suspended beside the edge rows under the ten-row condition, and the flowering period of each row was measured. The flowering periods of edge rows were slightly delayed by the shading treatment, but the flowering period uniformity was not improved markedly. In the third experiment, non-pinching, leaving a shoot per plant after pinching, and leaving two shoots per plant were compared under the four-row condition. Flowering period uniformity was improved in the two pinched experiment plots. In conclusion, spacing the center inter-row distance and training one or two shoots per plant improve the flowering period uniformity, which was influenced by the planting position and branching position after pinching.
In recent years, the need for cut flowers of spray-type chrysanthemums of approximately 70 cm in stem length, referred to as “eco-mum”, has been increasing to meet the bouquet processing demand from mass retailers. We examined the production technique for supplying “eco-mum” throughout the whole year. The target yield was 240,000 flowers per 10 a using direct cutting cultivation and harvesting four times a year. we investigated efficient production conditions: suitable cultivar selection, planting style, and the effects of dwarfing-agent treatments on the cut flower weight. Firstly, we selected suitable cultivars that can be harvested within 80 days for target achievement. As a result, among the autumn flowering chrysanthemum cultivars, ‘Celebrate’ and ‘Pisan’ were selected for their elongation ability, early flowering ability, and uniformity in growth and flowering. However, for harvesting in September, the high temperature period, it was necessary to use summer-to-autumn flowering types such as ‘Southern-Pegasus’ with a high temperature flowering ability. Secondly, we examined the effects of the planting style and density from 40,000 to 60,000 nursery plantlets per 10 a, including the aisle width, on the weight and number of flowers. As a result, although the weights of cut flowers were reduced when the planting number increased, the uniformity of the cut flower weight was improved by increasing the planting density of the aisle side. Thirdly, we investigated the effects of dwarfing-agent treatments on increasing the weight of cut flowers. In the greenhouse planted with 73,333 nursery plantlets per 10 a, the weights of cut flowers were increased significantly by applying a dwarfing-agent two times after turning the lights off. Combining these techniques, including the use of suitable cultivars, harvesting more than 60,000 cut flowers of “eco-mum” was possible, which is a 20–30-g weight at 70 cm in length (35 cm de-leaf) on 80-day cultivation. Furthermore, we demonstrated that it was possible to harvest 240,000 “eco-mum” flowers per 10 a harvesting four times a year, which corresponds to twice the yield using conventional cultivation.
There has been an increasing demand for “small-sized (mini) vegetables” in recent years because “they prevent even small families from wasting food”, and the present study focused on small-sized carrots. Although the demand for small-sized carrots is expected to increase further, it is difficult to distinguish them from processing carrots and “thinned-out carrots”, which are produced by harvesting gosun (six-inch) carrots earlier than the appropriate harvest period. In the present study, a survey was conducted to compare the forms and quality of small-sized and gosun carrots in their appropriate harvest periods and examine the characteristics of small-sized carrots; thinned-out carrots were distinguished from small-sized ones. A survey of their forms and yields was also conducted to determine the optimal planting densities. The lower the planting density of thinned-out carrots, the larger the size of the underground parts. On the other hand, the underground parts of small-sized carrots were not influenced by the planting density. Whereas the form of the roots of thinned-out carrots was conical, the roots of small-sized carrots were cylindrical, and the diameters of the roots were the same. The roots of small-sized carrots were softer than those of thinned-out ones. There was a significant correlation between the hardness and diameter of the roots of small-sized carrots, which suggests that the hardness of small-sized carrots is homogeneous and they can be consumed raw. In a comparison of carrots planted a intervals of 10 and 20 cm, there were no significant differences in the total yield, yield of high-quality products, or high-quality-product rate. However, the mean weight of the underground parts of carrots planted at intervals of 10 cm was lower than that of carrots planted at intervals of 20 cm, and within the shipment specification for small-sized carrots (20 to 30 g), which suggests that high-density cultivation is effective for small-sized carrots.
The efficiency of intermittent lighting for night-break (ILNB) with red (R) or red + far-red (R + FR) light was evaluated in the floral inhibition of chrysanthemum. ILNB schemes with various duty ratios had a lower efficiency on floral inhibition than continuous lighting with both R and R + FR. When ILNB (duty ratio: 0.5) was applied with the same accumulated amount of R light as in continuous lighting, the effect was the same. However, when the total ILNB irradiation was reduced by half, the effect was much lower than that after continuous R light irradiation. The results indicated that the effect of night-break depended on total irradiation. When the total lighting time was set at 18 min., the R ILNB effect of inhibition was same as continuous lighting, however, R + FR ILNB showed much stronger inhibitory effects than under continuous lighting. This could be because of the photoreversibility of responses by R and FR under continuous R + FR light conditions. In addition, the timing of night-break during the night affects the effectiveness of night-break. This should be considered when evaluating the effectiveness of ILNB. Nevertheless, we were unable to fully explain the effectiveness of ILNB schemes based on the results that were in accordance with the Pfr dark-reversion theory. Hence, in practice, one should not expect any advantage of ILNB schemes, because the photoreversibility of responses by R and FR light is not evident on long-term night-break irradiation under greenhouse cultivation.
Symptoms of cork spot like disorder, a physiological flesh disorder, in Japanese pear (Pyrus pyrifolia) ‘Akizuki’ and ‘Oushuu’ were investigated thoroughly by slicing fruit transversely at a 5-mm thickness. The symptoms were observed more markedly in the late maturing fruit in both cultivars, but especially in ‘Akizuki’. In addition, the severity of the disorder showed an association with the fruit fresh weights: more cork spots appeared on bigger fruit. More cork spots were observed in the middle of the fruit, with few at the stem end. However, they appeared on all parts of the fruit from the stem end to the calyx end, and then from the core to skin. Gibberellin paste treatment at 30–40 days after full flowering significantly increased cork numbers and made the disorder severe in both cultivars, although the rates of occurrence were not affected.
The degree of maturity of the kiwifruit ‘Rainbow Red’ (Actinidia chinensis) cannot be determined accurately because the progression of fruit ripening shows marked variation. Here, we evaluated the fruit characteristics by non-destructive testing using acoustic resonance measurements. The elasticity index determined from the second, third, and fourth resonant frequencies decreased with ripening. Strong correlations were found between acoustic resonance measurements and flesh firmness, soluble solid contents, and titratable acid levels. The ripening process from pre-harvesting to over-ripeness was divided into seven stages according to the elasticity index determined from acoustic resonance measurements. The optimal harvesting time was determined from the elasticity index from the second, third, and fourth resonant frequencies. The ripening patterns of the elasticity index were examined in identical fruit. The elasticity index was correlated with the flesh firmness measured using a fruit durometer, modeling the elasticity index and measurement value by single regression analysis. These findings suggested that acoustic resonance measurements were sufficiently accurate to determine the characteristics of the fruit, and that this is a useful alternative method to use for in the A. chinensis ‘Rainbow Red’.
We sought to establish a method of transportation that would retain the freshness of strawberry fruits. Two strawberry cultivars were transported to two countries in South East Asia by air and sea. We used new types of packages, as well as modified atmosphere packaging. During air transport, elastic film and hammock-type packaging reduced the level of damage and loss of firmness, respectively, in ‘Fukuoka S6’ and ‘Oishi berry.’ Quality protection offered by the packages differed depending on the cultivars; therefore, we indicate the necessity of selecting packages and cultivars. During sea transport, modified atmosphere packaging should be used in addition to the new packages because it prevented vascular anthocyanin loss, even though the new packages sufficiently reduced the level of damage to strawberry fruits. Furthermore, a high positive correlation was observed between the level of damage and percentage of damaged fruits, regardless of the use of the modified atmosphere packaging, type of cultivar, or transportation method. Based on this, the level of damage to strawberry fruits could be evaluated by the percentage of damaged fruits alone. In addition, it was suggested that improving the packages to reduce the percentage of damaged fruits could lower the level of damage simultaneously.