To improve wheat productivity, we investigated the relationships between wheat yield and growth- or field-related factors, and outline of cultivation in 26 cultivated fields. The results indicated that yield was significantly correlated with growth index （plant length × number of stems × leaf color/10000） at flag leaf emergence and leaf color at heading. In addition, in high-yielding fields, a high growth index value （about 120） was obtained at flag leaf emergence, and high leaf color was maintained at the heading stage. However, no correlation was found between yield and outline of cultivation, including the amount of nitrogen fertilizer applied. With regard to field-related factors, yield was significantly correlated with water retention time in the soil layer, ground water level, bulk density, and porosity of the subsoil. Therefore, to improve yield, it is necessary to improve the physical properties of the dense subsoil, to reduce the time of water retention in the soil layer due to heavy rainfall, and to reduce the number of days on which the groundwater level rises to < 40 cm below the ground surface. There were also significant correlations between the physical properties of the subsoil layer, the number of days the groundwater level rose to < 40 cm, and water retention time of the soil layer, suggesting that the water retention time of the soil layer could be reduced by improving the physical properties of dense subsoil and suppression of groundwater level rise.

Since harvesting work of cherry tomatoes requires a lot of labor, harvesting without calyx and cluster harvest have been investigated as a labor-saving harvesting method. The character of cherry tomatoes suitable for labor-saving harvesting include the detachabilities of calyx and fruit stalk, and the relationship of these character with the fruit character and their varietal difference in the colorning have been reported. However, no evaluation has been performed in a variety with a different fruit shape or maturation period other than the colorning. In this study, aiming at breeding of cherry tomatoes suitable for labor-saving harvesting, the detachabilities of calyx and fruit stalk were evaluated by maturation period using 4 varieties with different fruit shapes. The adhesion of calyx was positively correlated with the weight and the transverse diameter of the fruit, and the adhesion of fruit stalk was positively correlated with the vertical diameter of the fruit respectively, suggesting that the fruit character are involved in the detachabilities of calyx and fruit stalk. Therefore, the fruit character may be utilized as an index to select a strain or variety in the breeding of a cherry tomato variety suitable for labor-saving harvesting in consideration of harvesting without calyx and cluster harvest. In addition, the adhesion of calyx tended to decrease with fruit maturation. Therefore, for labor-saving harvesting, it is necessary to investigate the harvest time, changes in fruit quality, and freshness retention in consideration the fruit maturation period.

To discuss the extraction method of plant nutrients accumulated in crop residues, oilseed sunflowers were cultivated at different planting densities in a university farm in Tokyo, Japan. Sunflower stems were collected in the flowering, ripening and harvesting stages to obtain test materials with different traits. The dry matter yield of sunflower stems per unit planting area increased at higher planting densities. From the flowering to harvesting stages, the carbon content of plant nutrient elements contained in sunflower stems was slightly reduced, the nitrogen and phosphorus content was very slightly reduced, the potassium content was almost unchanged, and the calcium content was slightly increased. Each extraction ratio of specific plant nutrients elements in the liquid fraction obtained by hot-compressed water treatment to the original material element varied depending on the element. Thus, under the condition of 180ºC in temperature and 40 min in holding time, the extraction ratio for potassium ranged from 0.90 to 0.95; magnesium, 0.84 to 0.94; nitrogen, 0.78 to 0.85; phosphorus, 0.58 to 0.82; calcium, 0.31 to 0.64; and carbon, 0.32 to 0.40. The Nut / N ratio which is the ratio of the total amount of plant nutrients element in the original material to the amount of nitrogen element, and the C / N ratio which is the ratio of the amount of carbon element to the amount of nitrogen element, showed a strong linear relationship, and the same relationship was observed for the extracted nutrient elements in the liquid fraction. When the temperature of the hot-compressed water treatment was raised, the extraction ratio for carbon and calcium, which originally had relatively low extraction ratio, increased in proportion to the temperature, while the ratio for phosphorus decreased significantly. The effect of treatment retention time on the extraction ratios of plant nutrients was small for all elements.

This paper evaluates the potential performance and economic efficiency of the rice-transplanter（KUBOTA corporation, EP8D-GS） with automatic steering function in terms of operating accuracy and working efficiency. We confirmed that the rice-transplanter achieves high efficiency with the proper operating accuracy when the operator engages in supplying young seedlings using the automatic steering. This mode of operation has a large economic effect because of the reduction in the number of workers needed. However, there is a problem in the safety of this operation. The rice-transplanter is not equipped with a safety device that assumes that the operator seat is unoccupied. We concluded that we must further improve reliability in the design in order to overcome this drawback.

We investigated the effect of application of river sand to the underground parts on the initial growth of apple tree grafted on JM dwarfing rootstock. One year after planting, the height of ‘Kiou’ apple trees grafted on JM7 rootstock was higher with the application of river sand compared with trees grown without the application. In addition, the dry mass as well as the length and number of branches of two-year-old ‘Fuji’ nursery trees grafted on JM1 rootstock increased after river sand application. The results of this study demonstrate that the application of river sand to the underground parts of nursery trees promotes growth. This technique can be used for the production of robust apple nursery trees.

Previously, self-buildable and low-cost “Bamboo Greenhouses” (BGHs) were built as an experiment in Kumano city, Mie prefecture. Recently, BGHs have also been introduced in other prefectures. This study aimed to estimate the economic performance of farms that utilized BGHs and discuss their intended uses.

Farms that used BGHs in Mie prefecture were investigated. In Kumano city, a retiree took up farming and cultivated various vegetables. Their revenue was estimated to be 260,000～530,000 yen annually. Additionally, based on their net income ratio and the assumed depreciation cost of BGH, their income was estimated to be 120,000～400,000 yen annually. Therefore, BGHs were found to possess utility for commercial vegetable production and farming.

In addition to retired and returning farmers, a number of new farmers and rural-regeneration supporters also utilized BGHs. It was estimated that a typical full-time farmer would require 5–8 BGHs to earn a decent revenue. Full-time farmers, especially those who are not year-round farmers, can also use BGHs to expand the scale of their operations.