水耕キュウリの培養液非交換による収量の減少と活性炭添加による回復

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キュウリの養液栽培での生育後半の収量低下が培養液の非交換により引き起こされることを明らかにするとともに, その緩和方法について検討した.1. 培養液を2週毎に全量交換する場合と比べて培養液を追加していく場合, 栽培終了時の生育には影響がみられなかったが, 後半の果実収量が低下した.2. 追加液で栽培した場合, 収量低下には品種間差が認められ, '聖護院青長節成'および'PI 169391'で果実収量が低下したが, '北進'および'長日落合2号'では低下しなかった.3. 培養液を追加する栽培で活性炭を添加すると, 収量が低下しなかった.その現象の原因として活性炭に吸着されるような根からのしん出物の存在が考えられた.特にそのしん出物は, 若い果実に影響を及ぼすと考えられた.

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Experiments were conducted to clarify why fruit yield decrease during the late growing-period of cucumber cultured in hydroponic nutrient solution which was not completely renewed but only restored (a non-renewal culture). Furthermore, means to recover the decrease in fruit yield in the non-renewal culture system were investigated. 1. Vegetative growth was unaffected by biweekly total renewal or non-renewal of the culture solution. 2. When the culture solution was supplemented, the yield of 'Shogoin-aonaga-fushinari' and 'PI 169391' decreased, whereas that of 'Hokushin' and 'Chojitu-ochiai 2 gou' did not. 3. No decrease in fruit yield was observed when the solution was supplemented with nutrients and activated charcoal. This result suggests that root exudates had induced the decrease in fruit yield, especially by affecting young fruits, because the decrease was reversible through removal of the root exudates by the activated charcoal.