(27(1):37-46)INFLUNCE OF SOIL-MOISTURE DEFICIT AT DIFFERENT STAGES OF GROWTH ON THE DEVELOPMENT, YIELDS, NUTRIENTS AND WATER ABSORPTION OF TOMATO PLANTS

為闡明土壤乾燥對蕃茄生長，收量與養水分吸收的影響，辦理盆栽試驗。應用自動灌水裝置，適當控制透水速度，在蕃茄各生育期間加以土壤乾燥處理，並同時探討蕃茄對多量鉀肥的水分吸收效應。 蕃茄對水分的需求，依生育時期不同而有異。對土壤乾燥最能敏感反應的時期，乃是第一花房形成期以後的生育中期。土壤乾燥，不僅可使蕃茄果實收量與果實顆數減少，莖部的正常生長亦將受阻，因而影響及吸水能量，且其阻礙作用會持續至生育後期。蕃茄生育後期的土壤乾燥，對於果實顆數與平均果實顆重均無影響，因而果實收量亦不受影響。蕃茄植株的無機養分吸收，受土壤乾燥的影響較少。多施鉀肥，土壤乾燥更會增加鉀與鈣、鎂的拮抗作用，而減低蕃茄莖葉中的鈣、鎂含量。 The influence of soil-moisture deficit at different stages of growth on the development, yields, nutrients and water absorption of tomato plants was investigated with automatically controlling apparatus of watering in green house. The growing period of tomato plants was divided into three stages; 1) before the first florescence, 2) after the first florescence to the fourth florescence, 3) after the fourth florescence. A combination of two soil-moisture levels, 1J3 bar and 3 bar, and two levels of potash fertilizer with six treatments were allocated in split design. The results obtained are as follows: 1. The most moisture-sensitive period of tomato plants was the duration of the first flowering to the fourth flowering, which is the stage of flowering and fruit enlarging. The period after the fourth flowering to harvest was less sensitive. 2. Seasonal changes in water absorption of tomato plants showed that the amount of water absorbed per day ranged 100-130 ml at the period before the first florescence, then increased rapidly and reached maximum, 245-290 ml per day, during the second flowering and the fourth flowering, afterwards it dropped abruptly and then declined gradually, reaching to 200-150 ml per day while harvesting. 3. The amounts of water absorbed at each growing period of tomato plants were 3.4 litre per plant in the duration of plantation to the first florescence (30 days); 10.3 litre per plant in the duration of the first florescence to the fourth florescence (35 days); 9.1 litre per plant in the duration of the fourth florescence to harvest (50 days) totaling 22.8 litre per plant during the whole growing season. 4. Moisture stress during the first florescence and the fourth florescence resulted in significant decrease in fruit production and the number of fruit. The decrease in fruit production was primarilly induced by the elimination of fruit number. The average weight of individual fruit was also affected by moisture deficit at this period. After the fourth florescence, the number of fruit and the average weight of fruit was less aff ected. 5. Moisture deficit seemed to deteriorate the development of stem portion of tomato plants. It reduced markedly the dry matter weight of stem portion, presumably resulting in the reduction of water absorption. This trend was most apparent at the period of the first florescence to the fourth florescence when treated with high soil-moisture stress. The damage at this period also persisted until the latter stage of growth even though crop was provided with a sufficient supply of available water. 6. Soil-moisture stress did not affect the nutrient absorption of tomato plants much, but exagerated antagonistic competition between K and Ca, Mg when ample amount of potash fertilizer was applied