Departmental Bulletin Paper キャベツセル苗の根鉢形成前定植を可能にして定植後生育を促進する培養土ブロック化処理
Processing of Seeding Mixture into Firm Blocks for Transplantation of Cabbage Seedlings before Root Ball Formation to Promote Post-transplant Growth
キャベツ セルナエ ノ ネバチ ケイセイマエ テイチ ヲ カノウ ニ シテ テイショク ゴ セイイク ヲ ソクシン スル バイヨウド ブロックカ ショリ

髙畑, 健  ,  水島, 智史  ,  三浦, 周行  ,  Ken, Takahata  ,  Satoshi, Mizushima  ,  Hiroyuki, Miura

62 ( 2 )  , pp.62 - 67 , 2017-09-29
キャベツのセル苗は,根への障害を避けるため,根域を崩さずにセルからの抜き取りができる根鉢形成後に定植されている。しかし,根鉢形成苗は定植後の生育が遅いとされているので,根鉢形成前に,セル内培養土の形状を保ったまま,苗を抜き取ることができる培養土ブロック化方法を開発しようとした。処理区には,乾燥した場合100 gに相当する量の通常培養土に長さ約1 cmのヤシ殻繊維6 gおよびベントナイト10 gを混合した改良培養土をセルトレイ(128セル)に詰め,各セルに‘金系201号’種子を温室内で播種し,子葉展開期に0.6%ポリビニルアルコール水溶液を灌液する区を充て,3資材を用いずに通常培養土のみで育苗した区を慣行区とした。処理は出芽およびその後の芽生えの生育を抑制しなかった。慣行区では本葉3.0葉期が根鉢形成期であり,定植機による抜き取り苗の培養土部分は完全にセルの形を保っていた。同様なことが処理区では若い2.0および2.5葉期で観察された。慣行区3.0葉期苗に比べ,処理区2.0および2.5葉期苗はポット定植後の相対生長率が高く,定植後1週間の灌水制限および湛水をした場合も,その間の相対生長率が高かった。本実験の培養土ブロック化処理は,慣行よりも若い苗の定植を可能にし,育苗日数短縮に加え,定植後の生育を通常および水環境ストレス下で促進するのに有効であった。
Plug seedlings of cabbage that have formed root balls are removed easily from trays and can be transplanted without root damage. However, seedlings with root balls have been reported to show slow post-transplant growth. In this study, the authors developed a method for processing seeding mixture into blocks before root ball formation with the aim of increasing post-transplant growth. In the treated group, 6 g of 1 cm-long coconut shell fiber and 10 g of bentonite were added to ordinary seeding mixture, equivalent to 100 g in dry weight. The modified seeding mixture was used to fill 128 cell-trays. Under greenhouse conditions, seeds of ‘Kinkei No. 201’ were sown in the trays. A 0.6% aqueous solution of polyvinyl alcohol was applied to the trays when the cotyledons unfolded. In the control group, seedlings were grown in ordinary seeding mixture alone. The treatment did not suppress emergence or subsequent growth of the seedlings. In the control group, root balls were formed by the 3.0- leaf stage (3 true leaves). The seeding mixture maintained the shape of the cell, enabling the seedlings to be removed from the cells by a transplanting machine as usual. Similar shape maintenance of the seeding mixture was also observed in the treatment group, even at the 2.0 and 2.5- leaf stages. Compared to the 3.0-leaf stage seedlings in the control group, the relative growth rate was higher in the 2.0- and 2.5- leaf stage seedlings of the treated group after transplantation into pots containing growing mixture. Their relative growth rate was also high during the one-week period after transplanting, when the seedlings were stressed either by withholding water or by waterlogging. The seeding mixture block processing tested in this experiment enabled younger seedlings to be transplanted compared to conventional methods. This resulted not only in a reduction in the time taken to raise seedlings but also in the promotion of post-transplant growth under ordinary conditions, as well as under water stress.

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