To determine the optimal soil moistures at various growth stages of a Japanese pear (Pyrus serotina Rehd.) cv. ‘Kosui, ’ water content of the tree body was estimated by daily measurement of diameters of stem and fruit under various soil moisture conditions. The thresh-old values of the tension of soil moisture which did not give any severe water stress to the tree depended on the growth stages of fruit development; pF 2.40 at the cell division stage; pF 2.35 at the initial growth stage; pF 2.24 at the slow growth stage; pF 2.48 at the latter growth stage; and pF 2.29 at the full ripe stage. After the harvest of fruit, the value was pF 2.48. Photosynthetic rate declined 40% or more when the tension of the soil moisture became higher than pF 2.3. It is concluded that the threshold tension of soil moisture without severe water stress to the tree is pF 2.2-pF 2.40.

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This study was conducted to clarify the changes in nutrient uptake and its transport to plant organs during the developmental stage in tomato plants grown in the nutrient solution culture under the different seasonal conditions. Results are as follows. 1. The growth stage of tomato plant during the 110-day-culture period was divided into three growth stages. In the first 20 days after sowing, giving ‘leafy’ vegetative growth stage, the SGRs (Specific Growth Rate) of leaves were greater than those of stems. In the second stage from 30 to 70 days after sowing, giving ‘stemy’ vegetative growth stage, the SCRs of stem was greater than those of leaves. In the third stage during the period after 70 days from the sowing, giving fruit growth stage, the SGRs of fruits had the highest value as compared with those of leaves and stems. 2. The SARs (Specific Absorption Rate) of inorganic nutrients in plant were declined with age. Their SARs gave the maximum value in the order of N, K, P during the vegetative growth stage. In the fruit growth stage, the SARs of Ca in leaves were increased with age. The SARs of N and K in fruit were maintained at higher values during the period of fruits development. Inorganic nutrients required were N and K during the first and third (fruiting) stages, being P and Mg during the second stage. 3. The SARs of P and K in leaf, stem, and fruit were high in summer, whereas those of Ca were low in summer or high temperature season, although the SARs of Ca in aged leaves in summer were greater than those in winter. The uptake of Ca in an early stage of fruit growth was inhibited at high temperature.

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The effects of several chemicals on breaking bud dormancy in three Japanese persimmons (Diospyros kaki cv. ‘Hiratanenashi, ’ ‘Saijo, ’ ‘Fuyu’) were examined. Four chemicals were applied to the cuttings of 1-year-old twigs on November 9 and December 8; 1) leaching solution containing 20% lime nitrogen (55% CaCN₂), 2) 1/2-strength “Merit blue^®” (foliar fertilizer: N₂, 7%; P₂O₅, 5%; K₂O, 3%; Mn, 0.1%; B, 0.2%; Fe, 0.08%; Cu, 0.05%; Zn, 0.05%; Mo, 0.07%; Eizai Co. Ltd., Tokyo), 3) 500 ppm GA₃, 4) undiluted “garlic oil^®” (main component: allyl sulfide, Rikenkagaku Co. Ltd., Kyoto) . In early November, CaCN₂ was the most effective for bud-break, followed by “Merit blue” and the least effective was GA₃ among three cultivars. ‘Saijo’ was the most easy cultivar to break bud dormancy. In early December, when more than 50% of buds had been broken out dormancy, application of “Merit blue” and CaCN₂ accelerated bud-break of ‘Hiratanenashi’ and ‘Saijo’ by 5-7 days, while CaCN₂ was not so effective as “Merit blue” on ‘Fuyu.’ GA₃ slightly promoted bud-break of all cultivars in early November but did not in early December. Application of “garlic oil” was not only ineffective on the bud-break of three cultivars, but killed buds in the December treatment. As a whole, the effect of “Merit blue” was similar to or more than that of CaCN₂ for bud-break of three cultivars of Japanese persimmon.

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This study aims to establish the development of farmland from saline barren lands which is now attracting much attention in the world. There are several reasons for causing barren land like an unfavorable natural environment as deserts. Artificial caused include development. These activities have finally led the natural ecosystem to many unexpected tragedies. Moreover, they are causing land and soil erosion, floods and other disasters, producing vast areas of barren land. The theme of this study is to investigate methods how to improve saline soil caused by rock salt and convert it into arable land. This is one of the most difficult problems and no good results have been achieved, though some studies have been conducted on this subject. The author has obtained the following ideas through eight times of study abroad for the period of 1985 to 1993. The author found the characteristics of the natural ecosystem of salt-tolerant weeds that succession occurred according to the decrease in the salt concentration of the soil. These merits might be used in order to develop vegetation group artificially and turn barren land into fertile one.

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