Studies on production of vegetable crops in water culture V : Effect of O_2 concentration in nutrient solution on growth and yield of tomatoes (Agriculture)

トマト品種大型福寿を湛水循環方式により水耕栽培して, 通気-液循環用ポンプの稼動時間を5/60,5/30,5/15,25/30とする4区を設け, 培養液中の溶存酸素濃度の違いが春作と秋作のトマトの生育および収量におよぼす影響を調べた。溶存酸素濃度はポンプ稼動時間の長い区で高く保たれ, 日中, 特に14時前後に最低となり, その時の濃度は0.8ppmから6ppm以上まで大きな差異を示した。春作と秋作では気象条件が異なるにもかかわらず, 溶存酸素濃度の変化はやや似たパターンを示したが, 最低値は春作よりも秋作で高かった。本実験の範囲では通気-液循環は5/15区で充分であると認め, 最低溶存酸素濃度は2ppm以上と確認した。溶存酸素濃度の違いにより開花から果実収穫までの日数が影響を受けた。栽培終了時の植物体重量は溶存酸素濃度が高いほど大きかったが, 溶存酸素濃度を高めることによる重量増加には限界がみとめられた。本実験で行なった溶存酸素濃度の範囲では, 果実の収量におよぼす影響は僅かであった。春作および秋作とも溶存酸素濃度が高いほど1株あたりの養水分吸収量が大となる傾向がみられ, 特にCa, Mgでその影響が大きかった。植物体各部位の無機成分含有率におよぼす溶存酸素濃度の影響は僅かであった。果実の糖含有率は5/30区で最も高く, 他の区では低くなった。Tomato variety "Ohgata-Fukujyu" was watercultured to study the effect of O_2 concn in nutrient solution on growth and yield. Modified Hoagland's solution in culture beds were kept at constant level and a pump for areation and circulation was run for 5/60,5/30,5/15 or 25/30 minutes to obtain four levels of O_2 supply to the root. O_2 concn in the solution was maintained higher in beds where the pump was run for longer total period of time. It was often found at its lowest at around 2 : 00pm, when it varied from as low as 0.8 to over 6ppm, according to the pumping time. It was in general maintained higher in the fall crop than in the spring. In spite of differences in the climatic condition with the two crops, the changes in O_2 concns for the two followed a somewhat similar pattern. Aeration and circulation of 5/15 cycle was considered sufficient under conditions of the present experiment. An O_2 concn above 2ppm is recommended for a successful water culture of tomatoes. The time elapsed from anthesis to harvest of each fruit was affected by O_2 concn in nutrient solution. Plant weights at the time of termination of the experiment were higher with higher O_2 concns in nutrient solution, though there existed a certain limit for the increase. O_2 concn in nutrient solution affected the yield of tomatoes only a little, under conditions of the present experiment. Increased O_2 concn in nutrient solution tended to increase absorption of major nutrient elements and water, especially that of Ca and Mg. The effect on mineral content of each plant region was small. Sugar contents of fruit were highest with 5/30 cycle.departmental bulletin pape