JP2004008067A

JP2004008067A - Method for nutriculture of liquid supply control

Info

Publication number: JP2004008067A
Application number: JP2002165134A
Authority: JP
Inventors: Shinichi Tsunoda; 角田　真一; Hirotaka Sato; 佐藤　裕隆; Tadashi Ito; 伊東　正; Tatsu Maruo; 丸尾　達
Original assignee: Sumitomo Forestry Co Ltd
Current assignee: Sumitomo Forestry Co Ltd
Priority date: 2002-06-06
Filing date: 2002-06-06
Publication date: 2004-01-15

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for nutriculture of liquid supply control, with which a liquid supply is controlled based on the amount of solar radiation. <P>SOLUTION: A medium having ≥150 liters/m<SP>3</SP>readily effective water content, ≥50 liters/m<SP>3</SP>hardly effective water content, ≥20 cmols/kg cation exchange capacity and high physical/chemical buffer power is used as the medium. The liquid supply amount of a culture liquid per plant individual is adjusted to an amount to be supplied to 1 MJ/m<SP>2</SP>integral solar radiation, the waste liquid ratio of the culture liquid discharged to the outside of a culture system is adjusted to ≤15% of the liquid supply amount and the liquid supply is controlled to extremely efficiently and excellently cultivate a plant. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、固形培地を地面と隔離するため、容器や袋に植物育成用の培地を詰め、肥料と水を供給制御する養液栽培方法に関する。更に詳細には、培地が持つ物理的、化学的緩衝力を利用することにより、植物の吸水量に対応した安定的な給液管理が可能となり、さらに培地外に排出される廃液量を極力抑えることが可能な給液制御養液栽培方法に関する。
【０００２】
【従来の技術】
現在、主に普及している養液栽培方式を大別すると、湛液型循環式水耕、ＮＦＴ、固形培地耕がある。湛液型循環水耕には、ベッド内に一定量の培養液をたたえておき、これを間欠的・多量に強制循環、あるいは、少量の液を瀑気しながら間欠的に循環、または、各ベッド交互に、多量に交換させる方式などがある。ＮＦＴは、緩傾斜をつけたフィルム利用による水路状のベッドに、上方から培養液を少しずつ流下させ、タンクに戻して、液を循環させる方法である。これらの方法は、培地が液相だけで構成され、根の呼吸に必要な酸素は溶存酸素として供給される。根圏が単純で、根圏環境の制御がし易いという特徴を持つため葉菜類を中心とした大規模な植物工場的生産方式に適している。
これに対して、固形培地耕は礫、ロックウール等の培地を用いた養液栽培方式で、培地に固相、液相、気相の三相を有し、最も土耕に近い養液栽培である。固形培地耕における給液管理方法は、環境面への配慮から循環方式が推奨されているが、循環方式を導入するには初期の設置費用が高額になるため、普及させるにはコスト面で解決すべき課題がある。
これに対し、非循環方式として、余剰の培養液を施設系外へ排出するかけ流し方式や、近年、ヨーロッパを中心に普及が進んでいるバッグカルチャー方式等がある。特に、バッグカルチャー方式の利点として、（１）排水設備を持たず、培地を詰めた栽培用バッグをそのまま圃場に設置することから設置が簡便で安いこと、（２）万一病気が発生しても蔓延の危険性が少ないこと、（３）作物や栽培条件に合わせて適正な培地を利用できる等の利点がある。不利な点としては、バッグカルチャー方式の場合、廃液を回収する設備がないことから、バッグからの廃液がそのまま圃場へ排出されることになり、過剰に排出された場合には、肥料中の硝酸態窒素等が地下水を汚染する、あるいは肥料や水の浪費となることが考えられる。
【０００３】
固形培地耕における給液管理は主にタイマー方式によって行なわれているが、給液を必要以上に行った場合には、余分な液が排出されるため、実際は廃液量を見ながら、不足しないように過剰に与えているのが実情である。作物の生育状況や天候に基づいて、人間がタイマーの設定を変更するのは、なかなか困難であり、人為的ミスにより培養液に要する経費の増加等、経済的な損失、余剰液の処理問題をもたらす。
タイマー方式における上記の欠点を補うため、作物の吸水量に対応した給液を行うのが合理的と考えられることから、積算日射量に基づく給液方法の開発が行われ（特開平７−６７４８５号公報および特開２０００−１２５６８０号公報）、気候の変動が少ないヨーロッパ等では実用化されている。しかし、我が国では気候変動が大きく、日射量に対する植物の吸水量が年間を通じて一律でないこと、また実際の栽培試験に関する試験事例が少なく、一部の大規模温室を除き、ほとんど採用されていないのが現状である。
【０００４】
一方、固形培地耕で主に使用されているロックウールは、安価で、保水性があり、化学的に不活性で培養液の組成にほとんど影響を与えない培地である等の理由から最も普及しており、施設園芸の重要品目である果菜類、切り花等の栽培に用いられている。しかし、その特徴として、有効水分のほとんどがｐＦ１．８〜２．０の水分域に含まれているため、過湿になりやすく、また、一度乾燥すると、毛管水が断絶し、水みちができてしまうことがあり、また、肥料成分の吸着・溶出作用等、緩衝力がないために、肥料の集積、偏在を起こしやすいこと等のマイナス面もある。そのため、給液は培地内の肥料濃度を安定化させるために、廃液率が給液量の約２０〜３０％とする必要がある（最新　養液栽培の手引き；（社）日本施設園芸協会）。その他、使用される培地としてはロックウール以外に、礫や砂、もみがらくん炭、バーミキュライト、パーライト、ピートモス、おがくず、もみがら等があるが、一般土壌に比べるとロックウールとほぼ似たような特性を有している（小林ら．「ロックウールを用いたバッグカルチャーによる野菜栽培　第１、２報」；１９８８，１９８９．兵庫県立中央農業技術センター研究報告、中林ら；１９９０、関ら；１９９５、仁科ら；１９９８）。
【０００５】
【発明が解決しようとする課題】
上記の内容を勘案すると、バッグカルチャー方式を採用する際、環境面への配慮、肥料や水の浪費を防ぐ目的で、バッグからの廃液量を抑えるためには、日射比例方式により給液制御を行い、廃液率を低減すれば良いことがわかる。しかし、ロックウールをはじめこれまで検討されている培地資材を採用した場合には、培地内の肥料を安定化させるため、給液量の約２０％を排出する必要がある。もし、廃液率を抑えるため給液量を必要最小限にした場合には、培地内での水分の不均衡が生じ、また、化学的緩衝力が無いために、肥料バランスが崩れた場合には、植物が障害を起こしやすくなることが予想される。以上からバッグカルチャー方式による養液栽培方式における適正な培地としては、本発明者らが特開２０００１−１０３８５７号公報において提案した浄水場発生土、バーグ堆肥などからなる易効性水分量が１００リットル／ｍ^３以上で且つ難効性水分量が５０リットル／ｍ^３以上に調整された培地がある。この培地は物理・化学的緩衝力が高く望ましい培地であるが、この公開公報には日射比例方式を用いた給液管理については触れてない。
また、この公開公報に記載された給液条件では、植物が必要な分だけ給液されるため、肥料分についても過不足無く植物に供給されることが必要となり、過不足が生じた場合には植物が生理障害を引き起こす可能性が考えられる。
【０００６】
【課題を解決するための手段】
本発明は、植物を地面と隔離した固形培地で栽培し、給液管理を積算日射量に基づく日射比例方式で行う養液栽培方法において、
固形培地として易効性水分量が１５０リットル／ｍ^３以上、難効性水分量が５０リットル／ｍ^３以上で且つ陽イオン交換容量が２０ｃｍｏｌ／ｋｇ以上である固形培地を用い、
植物一個体当たりに供給する培養液の給液量を、積算日射量１ＭＪ／ｍ^２当たりに供給する量で調節して培地系外に排出される培養液の廃液率が給液量の１５％以下となるように給液制御する、
ことを特徴とする植物の養液栽培方法である。
本発明では、植物一個体当たりに供給する培養液の給液量を、積算日射量１ＭＪ／ｍ^２当たり４０ｍｌから２００ｍｌにして培地系外に排出される培養液の廃液率が給液量の１５％以下とすることができる。
本発明では、植物一個体当たりに供給する無機態窒素量を、積算日射量１ＭＪ／ｍ^２当たり２ｍｇ以上６ｍｇ以下として給液制御するのが好ましい。
【０００７】
【発明の実施の形態】
本発明は、植物を育成する際に、地面と隔離された栽培用培地を用いてバックカルチャー方式等で、積算日射量を基に培養液の給液管理を行なう養液栽培方法である。本発明の養液栽培方法は、通常、植物の成長度によって吸水量が左右されなくなったある程度成長した段階以降の植物の栽培に用いられる。例えば、トマトの場合には、一定の日射量に対して季節を問わず給液量が一定となる第２果房着果以降の栽培に適用される。
本発明では、培地として易効性水分量が１５０リットル／ｍ^３以上、好ましくは１８０リットル／ｍ^３以上、且つ難効性水分量が５０リットル／ｍ^３以上、好ましくは７０リットル／ｍ^３以上であり、且つ陽イオン交換容量が２０ｃｍｏｌ／ｋｇ以上、好ましくは３０ｃｍｏｌ／ｋｇ以上である物理的・化学的緩衝力の高い培地を用い、植物一個体当たりに供給する培養液の給液量を、積算日射量１ＭＪ／ｍ^２当たりに供給する量で調節して培地系外に排出される培養液の廃液率が給液量の１５％以下、好ましくは１０％以下、特に好ましくは５％以下となるように調整して給液制御することにより、植物を極めて効率よく良好に栽培することができる。本発明では、植物一個体当たりに供給する培養液の給液量を、通常、積算日射量１ＭＪ／ｍ^２当たり４０ｍｌから２００ｍｌにすることにより、培地系外に排出される培養液の廃液率が給液量の１５％以下、好ましくは１０％以下、特に好ましくは５％以下に調整することができる。本発明で言う廃液率とは給液量に対する廃液量の割合であり、植物の栽培期間中の平均で表す。
より具体的な本発明の効果としては、当該養液栽培方法により、培地外に排出される培養液の廃液量が極力抑えられるとともに、積算日射量に基づいて給液量を調節するため植物の吸水量に対応した給液管理が可能となる。このように給液量が積算日射量を基に必要最小限にされた場合には、天候の変動により植物の吸水量が大きく変動したとしても、植物に必要な水分を過不足なく供給することができ、曇天日には過剰な給液を行ない、過湿による害を引き起こすことなく、また、急な晴天でも積算日射量に対応した給液を行なうため、乾燥による植物への悪影響を回避することができる。また、栽培系外あるいは培地外に排出される廃液量をなくす、あるいは極端に少なくすることが可能となる。これにより、培養液の排出による浪費や、地下水汚染等の環境への悪影響を極力排除することが可能となり、循環方式で必要となる高価な設備、あるいは培養液をリサイクルするために必要な培養液の組成変更が必要でなくなる。
また、培養液の給液量は、積算日射量に基づいて調節するため、実質的には植物の吸水量と日射量との関係を考慮して調節することになり、従って、年間を通じて給液設定を大きく変更することなく、同一の管理で行うことができる。
更には、上記したように、易効性水分量、難効性水分量および陽イオン交換容量が特定量である物理的・化学的緩衝力の高い培地を用いた場合には、このような培地に培養液を供給した時に、培地内溶液のｐＨ値および電気伝導度（ＥＣ）が変動しにくいという効果が得られる。
【０００８】
本発明では、当該養液栽培方法において、植物一個体当たりに供給される窒素量が、積算日射量１ＭＪ／ｍ^２当たり２ｍｇ以上８ｍｇ以下、好ましくは４ｍｇ以上６ｍｇ以下であることが望ましい。窒素の供給方法は、培養液に窒素を含む肥料を添加してもよく、肥料を培地に直接添加してもよく、あるいはこれらを組み合わせたいずれでもよい。窒素形態はアンモニア態、硝酸態等のいずれの無機態窒素の形態でもよく、好ましくは硝酸態が全体の６０％以上含まれることが望ましい。また、窒素形態は、有機肥料、肥効調節型肥料、緩効性肥料などの有機態窒素の形態であってもよい。通常、無機態窒素は、硝酸カリウム、硝酸カルシウム、リン酸アンモニウムなどの窒素肥料の形態で、培養液に添加して用いられる。有機態窒素は、通常、有機肥料などを培地に直接添加して用いられる。
窒素以外のリン、カリウム、カルシウム、マグネシウム等の肥料の添加割合については、作物によって最も適したものが望ましいが、特に限定されるものではない。作物の窒素、リン、カリウム、カルシウム等の具体的な吸収量は、吸収濃度組成から重量換算すると（野菜試験場研究資料２１号、昭和６１．１１）、Ｎ：Ｐ：Ｋ：Ｃａ：Ｍｇの割合がＮを１０とした場合に、トマトの場合、１０：６．５：１６：１２：５となり、キュウリの場合、１０：５．３：１３：１５．４：５．３となり、イチゴの場合は１０：７：１６．７：１１．４：３．４となる。従って、これらの吸収量に応じて各肥料を添加すればよい。
本発明の栽培方法の場合、培養液の給液量は積算日射量によって制御されるため、実質的には植物の吸水量に対応していることとなるため、無機態窒素供給量も給液量に対して常に一定の濃度にすることが望ましい。例えば、以後の実施例に示すように、トマトの栽培試験を行なった結果では、トマトの吸水量が積算日射量１ＭＪ／ｍ^２当たり約７０ｍｌであることから、培養液の給液量は積算日射量１ＭＪ／ｍ^２当たり約７０ｍｌとし、この約７０ｍｌの給液量に対して４〜６ｍｇの無機態窒素を添加すれば良い。
本発明の養液栽培方法に従い培養液の給液を行なう場合、植物の吸水量に対応した水分が供給されるため、肥料分も吸収量に対応した量を供給しなければ、培地内で肥料が集積したり、不足する事態になることが予測される。本発明の効果として、上記に設定したように無機態窒素の肥料を供給することにより、植物に過不足なく肥料を供給することができる。また、上記した特定の培地を利用することにより、化学的な緩衝作用により、培地内溶液中の肥料濃度・組成の急激な変動を抑え、調整することが可能となり、植物の要素障害、例えば窒素欠乏症、窒素過剰症などの発生を回避できる。
【０００９】
本発明の積算日射量に基づいて給液制御する栽培方法に用いられる培地は、上記したように、易効性水分量が１５０リットル／ｍ^３以上、好ましくは１８０リットル／ｍ^３以上、且つ難効性水分量が５０リットル／ｍ^３以上、好ましくは７０リットル／ｍ^３以上であり、且つ陽イオン交換容量が２０ｃｍｏｌ／ｋｇ以上、好ましくは３０ｃｍｏｌ／ｋｇ以上である物理的・化学的緩衝力の高い培地が用いられる。
このような培地は、浄水場発生土、ゼオライト、バーミキュライト、パーライト、炭化物、一般土壌などの非有機質系資材の少なくとも１種と、バーク堆肥、ピートモス、ヤシガラ解砕物、もみがらなどの有機質系資材の少なくとも１種を混合して得られる混合物の易効性水分量、難効性水分量および陽イオン交換容量を測定し、それらが上記した特定の値を有するものを選択することにより得ることができる。
本発明の栽培用培地に用いる非有機質系資材の好ましい例としては、浄水場発生土を挙げることができる。浄水場発生土は浄水処理過程で発生する沈積泥土（浄水汚泥）を濃縮脱水した浄水ケーキが望ましい。浄水場発生土は凝集剤としてポリ塩化アルミニウムや硫酸アルミニウムを添加して沈殿処理され、無石灰処理により脱水されたものが望ましい。また、浄水場発生土は、含水率が４０重量％以上６０重量％以下、望ましくは５０重量％以上５５重量％以下に調整され、目開き２ｍｍの篩を通過するものが５０容量％以上９０容量％以下、目開き１０ｍｍの篩を通過し目開き２ｍｍの篩に残るものが１０容量％以上５０容量％以下の構成を有するのが望ましい。
【００１０】
非有機質系資材として浄水場発生土を用いた場合、浄水場発生土は浄水処理過程で添加されるアルミニウム化合物の影響でリン酸吸収係数が高いため、培地に肥料成分としてリン酸肥料を適当な量で添加するのが好ましい。リン酸肥料の添加量が少ないとリン酸欠乏を引き起こす。また、リン酸添加量が多いと土壌中の塩類濃度を高めて根に障害を及ぼしたり、リン酸肥料の副成分であるカルシウムやマグネシウム等が過剰となり培地中のミネラルバランスを損なう。また、果菜類に属す植物の栽培期間は長期にわたるため、持続的にリン酸成分を植物体に供給することが望ましい。ただし、リン酸肥料が含まれる液肥を供給する場合には、栽培開始時のリン酸欠乏を発生させずに、しかも培地の電気伝導度を上げることなく、また、カルシウムやマグネシウムが過剰でないリン酸肥料を使用することが望ましい。含有するリン酸成分が全体の２０重量％以上であり、そのうちく溶性リン酸が５０重量％以上であることが望ましい。リン酸肥料の種類については、熔リン、苦土過リン酸、熔成リン肥、重焼リン、熔過リン、リンスター（登録商標）、ダブリン（登録商標）、腐植リン等が例示される。培地に添加するリン酸肥料の量は、得られる培地１リットルあたりリン酸成分として１５００ｍｇ以上４０００ｍｇ以下、好ましくは２０００ｍｇ以上、３０００ｍｇ以下となる量が望ましい。
本発明培地で用いる浄水場発生土は、造粒されたものを用いることができる。造粒方法は転動造粒法あるいは押し出し造粒法のいずれでも良い。利用できる粒径は目開き１０ｍｍ以下であり、好ましくは８ｍｍ以下であることが望ましい。
【００１１】
非有機質系資材の一つである無機物として用いるゼオライトは、主にアナルサイム、モルデナイト、クリノプチノライトの３種類があり、特にモルデナイトとクリノプチノライトは陽イオン交換容量が高く、交換性陽イオン含量が高くアンモニウムイオンを選択的に吸着する性質を持っている。さらに物理性の改善効果として土壌の保水性特に易効性水分量、および透水性を高める効果があり、砂質土壌等保水性の低い土壌では、保水性を高める働きがあることから農業用として広く使われている。ゼオライトは、農業用として優れた効果を持つクリノプチロライトが最も望ましい。本発明では、ゼオライトを培地に添加することで、前述の無機質資材の効果のうち、培地の保水性、特に易効性水分量および透水性が向上され、前述の無機質資材の効果以外にとくに化学性を改良し、保肥力及び緩衝能が高い培地を得ることができる。
【００１２】
非有機質系資材の一つである無機物として用いられるバーミキュライトは、土壌改良材として市販のものであればいずれのものでも良い。バーミキュライトは蛭石を高温で焼成したもので、多孔質の軽い資材である。また、陽イオン交換容量が高い。このためバーミキュライトを培地に添加することで、とくに培地の主に易効性水分量が上昇し保水性が向上し、また、特に保肥力及び緩衝能が高い培地を得ることができる。
【００１３】
非有機質系資材の一つである無機物として用いられるパーライトは、真珠岩や黒曜石を粉砕して高温で焼成したもので、孔隙率が高く、軽量である。本発明では、保水性、即ち、易効性及び難効性水分量を高め、透水性を高める土壌改良材として、市販のものであればいずれのものでも良い。パーライトを培地に添加することで、特に透水性が向上し、また、高い気相率を有する培地を得ることができる。
【００１４】
非有機質系資材の一つである無機物として用いる炭化物は、土壌改良材として市販のものであればいずれのものでも良いが、炭の原料として木片、もみがら、食品汚泥等の植物質資材を炭化したものが好ましく用いられ、特に木片を炭化した木炭、もみがらを炭化したもみがらくん炭が望ましい。本発明では、炭を培地に添加することで、とくに培地の透水性が向上され、特に気相率が高い培地を得ることができる。また、炭に含有される各種ミネラル等の微量成分を植物に供給することができるため、化学性が長期にわたって維持された培地を得ることができる。
【００１５】
非有機質系資材の一つとして用いる一般土壌は、森林土壌（黒土、赤土、マサ土など）、水田土壌、畑土壌等の周辺土壌すべてを指す。これらの一般土壌は、種類によって有効水分量の特性に与える効果が異なり、団粒構造が発達している黒ボク土、畑土等、また、粘土含有量が高い赤土、水田土壌、森林土壌等は易効性水分量及び難効性水分量の有効水分量を高める効果が期待できる。これ以外の鹿沼土、砂壌土等は有効水分量を高める効果は期待できないが、気相率、透水性を高める効果が期待できる。
【００１６】
有機質系資材の一つとしてバーク堆肥を用いることができる。バーク堆肥は、特に浄水場発生土と組み合わせて用いるのが好ましい。バーク堆肥を用いることによって培地を膨軟化し、容積重が軽く扱いやすくなるだけでなく、適度な保水性を有する培地を得ることができる。また、堆肥化中に増殖した微生物相により培地の生物的緩衝力を高める効果がある。バーク堆肥を用いる場合のその使用量は、培地に対して３０容量％以上５０容量％以下となる量が望ましく、さらに望ましくは３５容量％以上４５容量％以下となる量である。バーク堆肥は広葉樹あるいは針葉樹の樹皮に鶏ふんや尿素などの窒素源を加えて長期間醗酵腐熟させたもので、土壌改良資材として政令指定されており、市販品であればいずれのものを用いることができる。バーク堆肥の粒径は１２ｍｍ以下が望ましく、１０ｍｍ以下のものがさらに望ましい。さらにバーク堆肥のＣ／Ｎ比が３５以下、全窒素含有量が１．０％以上１．４％以下、電気伝導度が１．０ｄＳ／ｍ以下のものが望ましい。バーク堆肥を使用することで、特にバーク堆肥中に含有する肥料成分が長期にわたり培地中に溶出して供給され、また含有する無機成分や腐植酸質の影響で化学的な緩衝能が高まることにより良好な培地の化学性を栽培期間中維持することができる。また、微生物の活性に必要な腐植等の炭素源が豊富に含まれているため、微生物相が活性化され植物に有害な病原菌が侵入した際に競合、及び拮抗作用により病原菌の拡散が防げるとともに、特に病害が発生しない限り消毒の手間が省ける。バーク堆肥は、針葉樹の樹皮を発酵して製造したものが望ましい。広葉樹に対して分解が遅いため長期間の使用した場合にも物理性を維持することができる。
【００１７】
有機質系資材の一つとして、ピートモスを用いることができる。ピートモスは保水性の向上を目的とした土壌改良材として政令指定されており、市販されているものであればいずれのものでもよい。ピートモスは、特に浄水場発生土と組み合わせて用いるのが好ましい。ピートモスを用いることで、特に保水性が高い培地を得ることができる。ピートモスの粒径は１２ｍｍ以下が望ましく、１０ｍｍ以下のものがさらに望ましい。ピートモス用いる場合のその使用量は、培地に対して５容量％以上２５容量％以下となる量が望ましく、さらに望ましくは１０容量％以上２０容量％以下となる量である。
【００１８】
有機質系資材の一つとしてヤシガラ解砕物を用いることができる。ヤシガラ解砕物は、ヤシの果肉部や木質部の組織を断裁して得られるものである。特公昭６３−５２８４８号公報、特公平６−２３号公報、特開平１−３１２９３４号公報等に記載されているように、ヤシガラ解砕物はそれ単独もしくは炭、肥料などを加えることによって、保水性、透水性、保肥性のバランスのとれた植物育成培地として利用されており、また、主に保水性の改善、保肥力の改善を目的とした土壌改良材として一般に市販されている。ヤシガラ解砕物は断裁の程度により、粉状の細かいものから直径３ｃｍ程度の粒径ものもがある。本発明で用いるヤシガラ解砕物は、粒径２ｍｍ以上１２ｍｍ以下のものが望ましい。粒径２ｍｍ以下のヤシガラ解砕物は保水性が著しく高く、透水不良の原因となり好ましくない。また、１２ｍｍ以上では培地内の物理性が不均一になり好ましくない。ヤシガラ解砕物を培地の有機質系資材として用いることで、培地の気相率が高く、透水性が向上した培地を得ることができる。
【００１９】
有機質系資材の一つとして、もみがらを用いることができる。もみがらとは、米を脱穀した際に得られる否可食部の繊維質資材を指す。もみがらは容易に崩れない構造を有しているため、培地の有機質系資材として用いることで、特に気相率が高く、透水性が向上された培地を得ることができる。用いるもみがらは粉砕等の加工がされておらず、形状がよく維持されたものが望ましい。
【００２０】
本発明に用いる養液栽培用培地は、上記した非有機質系資材と有機質系資材のそれぞれ少なくとも１種類を混合して得られる混合物の易効性水分量、難効性水分量および陽イオン交換容量を測定し、好ましくは、更にｐＨ値、電気伝導度（ＥＣ）およびｐＦ値を測定し、それらが上記した特定の値を有するものを選択することにより得ることができる。
非有機質系資材と有機質系資材の好ましい組み合わせとしては、例えば、浄水場発生土と、バーク堆肥及び／又はピートモスと、更に必要に応じてヤシガラ解砕物及び／又はもみがらとを用いる組み合わせ、あるいは浄水場発生土と、ゼオライト、バーミキュライト、パーライト、炭化物及び一般土壌から選ばれる少なくとも一種とを、バーク堆肥及び／又はピートモスと、更に必要に応じてヤシガラ解砕物及び／又はもみがらと共に用いる組み合わせなどが挙げられる。いずれにせよ、浄水場発生土を非有機質系資材の一つとして用いるのが好ましい。
【００２１】
本発明で用いる培地には、植物病原菌に拮抗性を有する拮抗微生物を添加しても良い。かかる微生物としては植物病原菌に拮抗性を有するものであれば、特に制限はなく、細菌類、放線菌類、真菌類などいずれも使用できる。これら微生物は、生菌類は勿論、生菌体を凍結保存したもの、凍結融解したものであっても良い。さらに異種間の二種又はそれ以上を同時に使用しても良い。微生物は、液体培養で得られるものは勿論、個体培養して得た胞子であっても良い。このような拮抗菌としては、例えば特公平３−６１４２４号公報、特公平３−６１４２５号公報などに記載されたものが挙げられる。より具体的には、土壌伝染性植物病原菌フザリウム（Ｆｕｓａｒｉｕｍ　ｓｐｐ）に拮抗性を有するバチルス・ライケルホルミス（Ｂａｃｉｌｌｕｓ　ｌｉｃｈｅｎｉｆｏｒｍｉｓ）、サーモアクチノマイセス　エスピー（Ｔｈｅｒｍｏａｃｔｉｎｏｍｙｃｅｓ　ｓｐ）及びペニシリウム　エスピー（Ｐｅｎｉｃｉｌｌｉｕｍ　ｓｐ）；土壌伝染性植物病原菌コルチシウム・ロルフシイ（Ｃｏｒｔｉｃｉｕｍ　ｒｏｌｆｓｉｉ）に拮抗性を有するアスペルギルス・テルリウス（Ａｓｐｅｒｇｉｌｌｕｓ　ｔｅｒｒｅｕｓ）及びトリコデルマ・ビリデ（Ｔｒｉｃｈｏｄｅｒｍａ　Ｖｉｒｉｄｅ）などが挙げられる。
【００２２】
これらの菌を実際に添加する場合は、培地に菌の培養液を添加して混合すれば良い。拮抗菌の添加量は養液栽培用培地１ｍ^３当り、通常培養液として５〜３０リットルである。拮抗菌の添加時期は、バーク堆肥を培地の有機質系資材として用いる場合には、バーク堆肥の堆積中でも良い。この場合、得られる養液栽培用培地は、バーク堆肥が添加されているため微生物的緩衝力が高く、さらに拮抗菌を添加することによって、立ち枯れ病菌が発生しても微生物の拮抗作用によって発生防除に有効である。また、特に病害が発生しない限り、栽培終了後も特に殺菌せずに、次作の作付けが可能となる。
【００２３】
以上に述べた培地用資材に加えて、主として物理性を調整するために、通常用いられる土壌改良材を添加してもよい。土壌改良材は物理性改善を目的として政令指定されたものや、培地原料として一般的に用いられているものならばいずれのものでもよい。
【００２４】
本発明の養液栽培方法を実施するには、例えば、培養液が廃液されるようにした、防水シートのバッグに本発明の培地を詰めて、あるいは長さ方向が１００〜１２０ｃｍ程度の防水シートで本発明の培地を包含し、栽培床を構成して栽培を行う。該防水シートは水と根を通さない素材のものであり、ポリオレフィン系（ポリエチレン、ポリプロピレン）フィルム、フッ素系フィルム、合成樹脂フィルム、防根シート、生分解性プラスティックフィルム等が使える。また、プラスティック、鉄骨、コンクリート、木材等で、上端が広く開口した固定式栽培床を構成し、これに培地を詰め、栽培床を作成して行うこともできる。
培養液は、水でも、あるいは水に前記した無機態窒素などの肥料成分等を添加したものでもよい。あるいは通常の植物栽培に用いる培養液でもよい。培養液は、設置した栽培床内に点滴、散水方式などの灌水チューブを設置し灌水を行うことによって培地に供給される。
本発明では、培養液は積算日射量に応じて培地に供給するため、通常、植物栽培が行なわれる適当な場所に日射センサーをセットし、日射量が測定される。測定値はカウンターによって積算され、設定された積算値に達すると、培養液の給液が開始するように潅水チューブなどをセットする。給液された培養液は流量計によって計量され、設定された一定の培養液を培地に供給するように設定される。これらの給液制御に使用する各種測定計、装置等は市販の製品を利用すればよい。本発明では、これらの給液制御により、好ましくは、一定の日射量に対して植物の給水量が生長量によって左右されない生育段階以降の植物に対して、植物一個体当たりに供給する培養液の給液量を、積算日射量１ＭＪ／ｍ^２当たりに供給する量で調節して培地系外に排出される培養液の廃液率が給液量の１５％以下、好ましくは１０％以下、特に好ましくは５％以下に調整する。本発明では、植物一個体当たりに供給する培養液の給液量を、上記した給液制御装置で、通常、積算日射量１ＭＪ／ｍ^２当たり４０ｍｌから２００ｍｌにセットすることにより、培地系外に排出される培養液の廃液率が供液量の１５％以下、好ましくは１０％以下、特に好ましくは５％以下に調整することができる。
また、例えば、培養液に無機態窒素を含む肥料を適当量添加して、同様にして、植物一個体当たりに供給される無機態窒素量が、積算日射量１ＭＪ／ｍ^２当たり２ｍｇ以上８ｍｇとなるように設定することができる。
植物栽培の際には、培養液を培地に供給した時に、その培地中の溶液のｐＨ値が５．０から７．５の範囲、特に５．５から７．０の範囲、また、電気伝導度（ＥＣ）（ｄＳ／ｍ）が０．８から２．５ｄＳ／ｍ、特に１．５から２．０ｄＳ／ｍの範囲となるように設定するのが好ましい。更には、ｐＦ値は通常１．５から３．２の範囲、特に品質より収量を優先したい場合には、１．５から２．４となるように、収量より品質を優先したい場合には、例えばトマトで言えば、糖度が６．５以上のものを採りたい場合には、２．４から３．２の範囲となるように設定するのが好ましい。本発明では、上記したように、易効性水分量、難効性水分量および陽イオン交換容量が特定量である物理的・化学的緩衝力の高い培地を用いるため、このような設定を比較的容易に行なうことができる。
【００２５】
【実施例】
次の実施例に基づいて本発明を更に詳細に説明するが、本発明はこれらの実施例によって何等制限されるものではない。
実施例１
積算日射量に基づく日射比例方式による給液管理において、適正な培地特性を把握するため、以下のような試験を行った。
（１）試験方法
供試植物はトマト‘ハウス桃太郎’を用い、子葉が展開した苗を、園芸用培養土を詰めた３号ポットに鉢上げし、本葉が６〜７枚展開したら栽培用バッグに定植し、４段果房上位２葉を残して摘心した。給液管理方法は、定植から２週間目まではタイマー方式により充分な給液を行い根の活着を促した。その後はすべての処理区において、表１に示すように、積算日射量１ＭＪ／ｍ^２当たりに供給する培養液の供液量を調節して培地からの培養液の栽培期間中の平均廃液率が給液量の１０％以下になるようにした。使用した培養液は園試処方とし、濃度が標準の１／２倍に調整されたものを使用した（具体的な組成は、Ｎ：８、Ｐ：２、Ｋ：８、Ｃａ：４、Ｍｇ：２ｍｅ／ｌ）。供試培地は、表１に示したように、保水特性を変えるため、ピートモスと浄水場発生土の混合比率を変えた組成とした。ピートモスは調整ピートを用い、浄水場発生土は浄水場から発生後、約３ヶ月間、堆積・切り返しにより堆肥化されたものを、目開き８ｍｍのフルイで調整し、さらにリン酸肥料を浄水場発生土１リットル当たりリン酸分として２０００ｍｇ添加したものとした。また、培地としてそれぞれロックウール、籾殻くん炭、ピートモスを用いた試験も同様に行った。各処理培地は１０リットル用のプラスティックフィルム製のバッグに詰め、バッグの高さが約１５ｃｍになるように形状を整え発砲スチロール製のベッドに設置した。発泡スチロール性の栽培用ベッドはバッグからの廃液が回収できるようにした。定植は１バッグにつき２株を定植した。
調査項目は、供試培地の保水特性として、易効性水分量と難効性水分量を求め、また栽培終了時の培地のｐＨと電気伝道度（ＥＣ）を測定した。植物体の調査は生育と収量を測定した。
【００２６】
【表１】

【００２７】
（２）試験結果
表２に培地の有効水分量と陽イオン交換容量（ＣＥＣ）を示した。易効性水分量は浄水場発生土の割合が増えるに従い、徐々に減少し、難効性水分量は増加した。ＣＥＣは浄水場発生土の混合割合の増加に従い高まり、ロックウール、籾穀くん炭およびピートモスでは１０ｃｍｏｌ／ｋｇ以下を示した。
【００２８】
【表２】

【００２９】
表３に栽培終了時における培地のｐＨとＥＣを示した。ｐＨは１０、２０容量％区で８．５以上と高く、３０〜８０容量％区では５〜７を示した。ロックウールとくん炭で８以上と高く、ピートモスでは５以下と低かった。ＥＣについて、１０、２０容量％区が他区に比べ顕著に高く、浄水場発生土の混合割合が高まるに従い低くなり、３０〜８０容量％区では２前後を示し、ロックウール、籾穀くん炭およびピートモスでは３〜５と高い値を示した。
【００３０】
【表３】

【００３１】
表４に地上部生体重と収量を示した。葉と茎の生体重は１０容量％区より浄水場発生土の混合割合が高まるに従い増加し、３０〜６０容量％区では５００ｇ以上を示した。収量は４０、５０、６０容量％区が１０、２０、３０、７０、８０容量％区と比べ顕著に高く、１株当たり３０００ｇ前後を示し、これに対しロックウール、籾殻くん炭およびピートモスでは２０００ｇ前後となった。
【００３２】
【表４】

【００３３】
以上から、積算日射量１ＭＪ／ｍ^２当たりの培養液の供液量を調節して廃液率が１０％以下となるように給液制御して養液栽培する場合に、用いる培地は、易効性水分量が１５０リットル／ｍ^３以上、難効性水分量が５０リットル／ｍ^３以上、陽イオン交換容量（ＣＥＣ）が２０ｃｍｏｌ／ｋｇ以上であることが望ましいことが判明した。
【００３４】
実施例２
本実施例では、日射比例方式で給液管理を行う栽培方式において、使用する培地特性として適正な陽イオン交換容量を検討した。
（１）試験方法
供試植物はトマト‘ハウス桃太郎’を用い、栽培方法は実施例１に準じた。給液管理方法は、実施例１と同様、定植から２週間目まではタイマー方式により充分な給液を行い、根の活着を促した。その後は表５に示した各処理区に移植して、表６に示すように、積算日射量１ＭＪ／ｍ^２当たりに供給する培養液の供液量を調節して培地からの培養液の栽培期間中の平均廃液率が給液量の１０％以下になるようにした。使用した培養液は園試処方とし、濃度が標準の１／２倍に調整されたものを使用した（具体的な組成は、Ｎ：８、Ｐ：２、Ｋ：８、Ｃａ：４、Ｍｇ：２ｍｅ／ｌ）。供試培地は、調整済みのピートモスに赤土を２０容量％混合したものとし、有効水分量は易効性水分量が１８５リットル／ｍ^３、難効性水分量が８０リットル／ｍ^３であった。表５に示したように、処理区は調整した培地にゼオライトを培地１リットル当たり２ｇずつ添加することにより陽イオン交換容量の異なる培地を７種類作成した。
調査項目は供試培地の陽イオン交換容量、難効性水分量および易効性水分量、栽培期間中の培地内溶液のｐＨとＥＣ、植物については収量、奇形果発生率とした。
【００３５】
【表５】

【００３６】
【表６】

【００３７】
（２）試験結果
得られた結果を表７、表８および表９に示した。
表７から分かるように、栽培期間中の培地内溶液のｐＨは、２、４ｇ区では時間の経過とともに上昇し、定植後２ヶ月目には８．０以上となり、ゼオライトの添加量が６ｇ以上の区では６．０から７．０を示した。
【００３８】
【表７】

【００３９】
表８から分かるように、培地内溶液のＥＣは２ｇ、４ｇ区では定植後、時間の経過とともに急激な上昇がみられ、２ヶ月後には３．５ｄＳ／ｍ以上となった。一方、ゼオライト添加量が６ｇ以上の区では１．０〜２．０ｄＳ／ｍを示した。
【００４０】
【表８】

【００４１】
表９から分かるように、収量は２ｇ、４ｇ区が他区に比べ低く、ゼオライト添加量が６ｇ以上の区では顕著に高くなり、１０ｇよりゼオライトの添加量が多い区では３０００ｇ以上を示した。全収穫個数に対する奇形果発生率は２、４ｇ区が他区に比べ高く、ゼオライトの添加量が６ｇ以上の区では顕著に低くなり１０％以下となった。
【００４２】
【表９】

【００４３】
以上から、給液管理を積算日射量を基に、廃液率が１０％以下になるように行った場合には、使用する培地のＣＥＣは２０ｃｍｏｌ／ｋｇ以上、好ましくは３０ｃｍｏｌ／ｋｇ以上であることが望ましいことが判った。
【００４４】
実施例３
本実施例では、積算日射量を基に給液管理を行う場合、廃液率の違いがトマトの収量、品質に及ぼす影響を調査した。
（１）試験方法
供試植物はトマト‘ハウス桃太郎’を用い、子葉が展開した苗を、園芸用培養土を詰めた３号ポットに鉢上げし、本葉が６〜７枚展開したら栽培用バッグに定植し、４段果房上位２葉を残して摘心した。給液管理方法は、積算日射量を基ににした日射比例方式と、比較例としてタイマー方式を採用した。日射比例方式では培地から排出される培養液の給液量に対する廃液率を変えるため、表１０に示したように、積算日射量１ＭＪ／ｍ^３当たりの給液量を２０〜２４０ｍｌの１２水準に設定し、タイマー方式は給液量の２０％が廃液されるように給液量を設定した。培養液は実施例１と同じものを用いた。使用する培地はピートモス：バーク堆肥：浄水場発生土が３：３：４の容量割合で混合された物を使用し、ピートモスと浄水場発生土の調整は実施例１に準じて行い、バーク堆肥は針葉樹を原料にし熟成したものを目開き８ｍｍの篩を通過したものを使用した。調整された培地は、易効性水分量が１５２リットル／ｍ^３、難効性水分量が８２リットル／ｍ^３、ＣＥＣは２２ｃｍｏｌ／ｋｇであった。また、定植から２週間までは水のみを給液し、その後は園試処方の１／２倍濃度の培養液を給液した（具体的な組成は、Ｎ：８、Ｐ：２、Ｋ：８、Ｃａ：４、Ｍｇ：２ｍｅ／ｌ）。
調査項目は、栽培期間中における培地内の水分状態と給液量に対する廃液率を求め、培地内の水分状態はセラミック式土壌水分計を用いて行った。植物体は収量と品質の指標としてＢｒｉｘ糖度、および生理障害の発生率とした。
【００４５】
【表１０】

【００４６】
（２）試験結果
得られた結果を表１１、表１２および表１３に示した。
表１１から分かるように、廃液率は８０ｍｌ区では０となり、１００ｍｌ区より給液量が多い区では、給液量の増加に伴い徐々に増え、給液量が２２０、２４０ｍｌ区およびタイマー方式では２５〜３５％以上を示した。
【００４７】
【表１１】

【００４８】
表１２から分かるように、培地内溶液のＥＣは２０〜６０ｍｌ区では８以上を示し、給液量が多くなるに従い、徐々に低下した。ｐＦ値は２０〜６０ｍｌ区では３〜３．５を示し、給液量が増えるに従い徐々に低下し、給液量が２２０、２４０ｍｌ区、タイマー方式では１．５以下と飽和状態となった。
【００４９】
【表１２】

【００５０】
表１３はトマトの収量、品質について示している。収量は２００ｍｌ区までは給液量の増加に伴い高まり、給液量がさらに多い区では減少し、４０ｍｌ区以下と２２０ｍｌ区以上はタイマー方式に比べ低かった。Ｂｒｉｘ糖度は給液量の増加とともに低下し、２００ｍｌ区以下では６．０以上であったが、２２０、２４０ｍｌ区では急激に低下し、５以下となった。生理障害について、尻腐れ果は給液量が少ないと発生する傾向がみられ、給液量の増加とともに徐々に減少し、１４０ｍｌ区以上では発生率は０％であった。裂果は逆に給液量が多い区で発生率が高く、１６０ｍｌ区以下では０であったが、１８０ｍｌ区以上では給液量が増えるに従い高まり、２２０ｍｌ区以上で急激な増加が見られた。
【００５１】
【表１３】

【００５２】
以上から、積算日射量に基づき給液制御を行った場合、トマトの収量と品質は給液量によって大きく左右され、給液量が４０ｍｌ以下では、植物は極端な水分ストレスを受け、糖度は高まるものの、尻腐れ果が多発し収量は減少した。一方、極端に給液量が多い場合には、培地内が過湿条件となり、裂果が多発した。このことから、積算日射量を基にした給液制御によりトマトを栽培する場合には、一株（一個体）当たりの培養液の給液量を、日積日射量１ＭＪ／ｍ^２当たり６０ｍｌ以上２００ｍｌとして、廃液率が１５％以下とするのが望ましいことが判った。
【００５３】
実施例４
本実施例では、日射比例方式による給液管理を行った場合の適正な窒素の供給量を検討した。
（１）試験方法
供試植物はナス科のトマト、ウリ科のキュウリ、バラ科のイチゴを用い、供試培地はピートモス：バーク堆肥：浄水場発生土が３：３：４の容量割合で混合した培地を使用し、個々の資材の調整は実施例１に準じた。供試培地の有効水分量は、易効性水分量１６８リットル／ｍ^３、難効性が９０リットル／ｍ^３、ＣＥＣが２０ｃｍｏｌ／ｋｇであった。栽培方法について、トマトは実施例１、２に準じた。キュウリは供試品種に穂木‘シャープ３０１’を、台木に‘ゆうゆう一輝’を用い、整枝は主枝１６節摘心、１次側枝を１節摘心、２次側枝以降を放任とした。イチゴは供試品種に‘女峰’を用い、９月上旬に定植し１月から５月まで収穫を行なった。
培養液は園試処方を基準とした。更に表１４に示すように各処理区で培養液中の窒素添加量を変動させた。窒素添加量は、硝酸カリウム、硝酸カルシウムの量を調節し、その他の肥料組成（Ｐ：Ｋ：Ｃａ：Ｍｇの組成がトマトの場合、２：４：３：２ｍｅ／ｌ、キュウリの場合、３：６：７：４ｍｅ／ｌ、イチゴの場合、１：５：３：２：１ｍｅ／ｌ）は各処理区間で同量になるように調節した。
調査項目は栽培期間中の給液量及び廃液率並びにトマト、キュウリ及びイチゴの収量および窒素欠乏症と過剰症、栽培期間中の培地内溶液のＥＣとした。
【００５４】
【表１４】

【００５５】
（２）試験結果
得られた結果は表１５、表１６および表１７に示した。
表１５から分かるように、収穫時における培地内溶液のＥＣは供試植物の種類に係わらず、窒素添加量の増加とともに上昇した。トマトでは窒素添加量２ｍｇで、キュウリでは４ｍｇ以下で０．５ｄＳ／ｍ以下となり適正域を下回った。また、高濃度域ではトマトが窒素添加量７ｍｇ以上で、キュウリが９ｍｇ以上で、イチゴが７ｍｇ以上で３．０ｄＳ／ｍ以上と植物の適正域を上回る高い値となった。
【００５６】
【表１５】

【００５７】
表１６から分かるように、トマトは１ｍｇ区から窒素添加量の増加に伴い増加し、６ｍｇ区を境に添加量の増加に伴い急激に減少し、タイマー方式より収量が高かったのは４ｍｇ以上６ｍｇ以下であった。キュウリは１ｍｇ区から窒素添加量の増加に伴い増加し、８ｍｇ区をピークに徐々に減少し、タイマー方式より収量が高かったのは４ｍｇ以上８ｍｇ以下であった。イチゴは１ｍｇ区から窒素添加量の増加に伴い増加し、４ｍｇ区を境に徐々に減少し、タイマー方式に比べ収量が高かったのは２ｍｇ〜５ｍｇ区であった。
【００５８】
【表１６】

【００５９】
表１７に供試植物の窒素欠乏症と過剰症の目視による判定結果を示した。欠乏症は下位葉の黄化が認められたものを欠乏症とし、過剰症は富窒素栄養条件下で栄養生長過多による収量低下が認められたものとした。その結果、欠乏症は、トマトでは３ｍｇ以下、キュウリでは２ｍｇ以下、イチゴでは１ｍｇ以下で認められ、過剰症は、トマトでは、８ｍｇ以上、キュウリでは９ｍｇ以上、イチゴでは７ｍｇ以上で認められた。
【００６０】
【表１７】

【００６１】
以上から、一株（一個体）当りの培養液の無機態窒素量を、積算日射量１ＭＪ／ｍ^２当たり２ｍｇ以上８ｍｇ以下として給液制御するのが好ましく、特に４ｍｇ以上６ｍｇ以下とするのが好ましいことが判った。
【００６２】
【発明の効果】
以上の結果から明らかなように、本発明では、培地として易効性水分量が１５０リットル／ｍ^３以上、難効性水分量が５０リットル／ｍ^３以上、且つ陽イオン交換容量が２０ｃｍｏｌ／ｋｇ以上である物理的・化学的緩衝力の高い培地を用い、植物一個体当たりに供給する培養液の給液量を、積算日射量１ＭＪ／ｍ^２当たりに供給する量で調節して培地系外に排出される培養液の廃液率が給液量の１５％以下となるように調整して給液制御することにより、植物を極めて効率よく良好に栽培することができる。当該養液栽培方法により、培地外に排出される培養液の廃液量が極力抑えられるとともに、積算日射量に基づいて給液量を調節するため植物の吸水量に対応した給液管理が可能となる。更に、当該養液栽培方法において、植物一個体当たりに供給される無機態窒素量を積算日射量１ＭＪ／ｍ^２当たり２ｍｇ以上８ｍｇ以下とすることにより、植物に過不足なく肥料を供給することができ、例えば窒素欠乏症、窒素過剰症などの発生を回避できる。[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a nutrient solution cultivation method in which a container or a bag is filled with a medium for plant growth in order to isolate a solid medium from the ground, and supply of fertilizer and water is controlled. More specifically, by utilizing the physical and chemical buffering power of the culture medium, stable liquid supply management corresponding to the amount of water absorbed by the plant becomes possible, and the amount of waste liquid discharged outside the culture medium is minimized. The present invention relates to a liquid supply control nutrient cultivation method capable of supplying liquid.
[0002]
[Prior art]
At present, the widely spread nutrient cultivation methods are roughly classified into submerged circulation type hydroponic culture, NFT, and solid culture cultivation. In a submerged circulating hydroponic system, a certain amount of culture solution is accumulated in a bed and forcedly circulated intermittently and in large quantities, or intermittently circulated with a small amount of liquid flowing through the bed. There is a method of changing a large number of beds alternately. The NFT is a method in which a culture solution is gradually flown down from above into a channel-like bed using a film having a gentle slope, and is returned to a tank to circulate the solution. In these methods, the medium is composed of only the liquid phase, and oxygen required for root respiration is supplied as dissolved oxygen. It has characteristics that the rhizosphere is simple and the rhizosphere environment can be easily controlled, so that it is suitable for a large-scale plant factory-based production system mainly for leafy vegetables.
On the other hand, solid culture cultivation is a nutrient solution cultivation method using a medium such as gravel, rock wool, etc., which has three phases of solid phase, liquid phase, and gas phase in the medium, and is the closest to soil cultivation. It is. For the liquid supply management method in solid medium cultivation, the circulation method is recommended from the viewpoint of environmental considerations, but the initial installation cost is high to introduce the circulation method, so it is cost effective to spread it There are issues to be addressed.
On the other hand, as a non-circulation method, there are a pouring method in which excess culture solution is discharged out of the facility system, and a bag culture method, which has recently become popular mainly in Europe. In particular, the advantages of the bag culture method include (1) simple and inexpensive installation because a cultivation bag packed with a culture medium is directly installed in a field without a drainage system, and (2) a disease occurs. Also has the advantage that (3) an appropriate medium can be used according to crops and cultivation conditions. Disadvantages are that, in the case of the bag culture method, there is no equipment for collecting waste liquid, so waste liquid from the bag is discharged to the field as it is. Nitrogen and the like may contaminate groundwater or waste fertilizer and water.
[0003]
Liquid supply management in solid medium cultivation is mainly performed by a timer method, but if liquid supply is performed more than necessary, excess liquid will be discharged, so do not run short while checking the waste liquid amount actually The fact is that they are giving too much. It is very difficult for humans to change the timer setting based on the growth status of the crop and the weather. Bring.
In order to compensate for the above-mentioned drawbacks in the timer method, it is considered reasonable to supply water according to the amount of water absorbed by the crop. Therefore, a liquid supply method based on the integrated amount of solar radiation has been developed (Japanese Patent Laid-Open No. 7-67485). And Japanese Patent Application Laid-Open No. 2000-125680), and are practically used in Europe and the like where climate change is small. However, in Japan, climate change is large and the amount of water absorbed by plants with respect to the amount of solar radiation is not uniform throughout the year, and there are only a few cases of actual cultivation tests. It is the current situation.
[0004]
On the other hand, rock wool, which is mainly used in solid medium cultivation, is the most popular because it is inexpensive, has water retention, is chemically inert and has little effect on the composition of the culture solution. It is used for cultivation of fruits and vegetables and cut flowers, which are important items of greenhouse horticulture. However, as a feature, most of the effective moisture is contained in the moisture range of pF 1.8 to 2.0, so it tends to be over-humidified, and once dried, the capillary water is cut off, and the water path is formed. In addition, since there is no buffering force such as the adsorption and elution of fertilizer components, there is a downside that fertilizer is likely to accumulate and be unevenly distributed. Therefore, in order to stabilize the concentration of fertilizer in the culture medium, it is necessary to make the waste liquid rate about 20 to 30% of the amount of the liquid supply (Guide to the latest hydroponic culture; Japan Institute of Horticulture) . In addition, besides rock wool, besides rock wool, there are gravels, sand, rice husk charcoal, vermiculite, perlite, peat moss, sawdust, rice husk, etc., but it is almost similar to rock wool compared to general soil (Kobayashi et al., "Vegetable Cultivation by Bag Culture Using Rock Wool 1st and 2nd Report"; 1988, 1989. Hyogo Prefectural Central Agricultural Technology Center Research Report, Nakabayashi et al .; 1990, Seki et al .; 1995, Nishina et al., 1998).
[0005]
[Problems to be solved by the invention]
Considering the above, when adopting the bag culture system, in order to consider the environment and prevent waste of fertilizer and water, in order to reduce the amount of waste liquid from the bag, supply control by the solar radiation proportional method It can be seen that it is sufficient to reduce the waste liquid rate by performing the method. However, when a medium material such as rock wool, which has been studied so far, is used, it is necessary to discharge about 20% of the supplied liquid in order to stabilize the fertilizer in the medium. If the supply volume is minimized to reduce the waste liquid rate, the imbalance of water in the culture medium will occur, and if there is no chemical buffering power, the fertilizer balance will be lost. It is expected that plants will be more prone to failure. From the above, as an appropriate medium in the nutrient solution cultivation method by the bag culture method, a water purification plant generated soil proposed by the present inventors in Japanese Patent Application Laid-Open No. 20001-103857, an easily available water amount composed of berg compost, etc. is 100 liters. / M ³ Above and the ineffective moisture content is 50 l / m ³ There is a medium prepared above. Although this medium is a desirable medium having high physical and chemical buffering power, this publication does not mention liquid supply management using a solar radiation proportional method.
In addition, under the liquid supply conditions described in this publication, the plant is supplied only as much as necessary, so that it is necessary that the fertilizer component be supplied to the plant without excess or deficiency. May cause physiological disorders in plants.
[0006]
[Means for Solving the Problems]
The present invention is a nutriculture method for cultivating plants in a solid medium isolated from the ground and performing liquid supply management in a solar radiation proportional system based on the integrated amount of solar radiation.
Easy-to-use water content of 150 liter / m as solid medium ³ As described above, the ineffective moisture content is 50 liters / m. ³ Using a solid medium having a cation exchange capacity of 20 cmol / kg or more,
The amount of culture solution to be supplied per individual plant is calculated as the integrated solar radiation amount of 1 MJ / m ² The supply is controlled so that the waste liquid ratio of the culture liquid discharged out of the culture system by adjusting the supply amount per unit is 15% or less of the supply amount.
A method for nutrient cultivation of a plant, characterized in that:
In the present invention, the amount of the culture solution supplied per individual plant is defined as the integrated solar radiation amount of 1 MJ / m ² The volume of the culture solution discharged from the culture system at 40 ml to 200 ml per volume can be 15% or less of the supplied amount.
In the present invention, the amount of inorganic nitrogen supplied per individual plant is calculated as the integrated solar radiation amount of 1 MJ / m ² It is preferable to control the liquid supply to be 2 mg or more and 6 mg or less.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is a nutrient solution cultivation method for managing the supply of a culture solution based on an integrated amount of solar radiation by a back culture method or the like using a culture medium isolated from the ground when growing a plant. The nutrient solution cultivation method of the present invention is generally used for cultivation of plants after the stage of growing to some extent where the water absorption is no longer influenced by the growth degree of the plants. For example, in the case of tomatoes, the present invention is applied to cultivation after the second fruit set, in which the supply amount is constant regardless of the season with respect to a fixed amount of solar radiation.
In the present invention, the medium has an easily available water content of 150 l / m 2. ³ Above, preferably 180 l / m ³ Above and the ineffective moisture content is 50 l / m ³ Above, preferably 70 l / m ³ And a medium having a high cation exchange capacity of at least 20 cmol / kg, preferably at least 30 cmol / kg, and having a high physical and chemical buffering power, and the amount of culture solution to be supplied per plant is determined. , Integrated solar radiation 1MJ / m ² The amount of the culture solution discharged out of the culture system by adjusting the amount supplied per unit is adjusted to be 15% or less, preferably 10% or less, particularly preferably 5% or less of the supply amount. By controlling the liquid, the plant can be cultivated very efficiently and favorably. In the present invention, the supply amount of the culture solution supplied per plant is usually set to an integrated solar radiation amount of 1 MJ / m ² By making the volume per 40 ml to 200 ml, the waste liquid rate of the culture solution discharged out of the medium system can be adjusted to 15% or less, preferably 10% or less, particularly preferably 5% or less of the supplied amount. The waste liquid ratio as referred to in the present invention is the ratio of the amount of waste liquid to the amount of liquid supplied, and is expressed as an average during the plant cultivation period.
As a more specific effect of the present invention, the nutrient solution cultivation method minimizes the amount of waste liquid of the culture solution discharged outside the culture medium, and adjusts the amount of liquid supply based on the integrated amount of solar radiation. Liquid supply management corresponding to the amount of water absorption becomes possible. If the amount of liquid supply is minimized based on the integrated amount of solar radiation in this way, even if the water absorption of the plant fluctuates greatly due to weather fluctuations, supply the necessary water to the plant without excess or shortage. It is possible to avoid excessive damage to plants due to overdriving on cloudy days without causing harm caused by over-humidity. be able to. Further, it is possible to eliminate or extremely reduce the amount of waste liquid discharged outside the cultivation system or outside the culture medium. This makes it possible to minimize waste of the culture medium and adverse effects on the environment such as groundwater contamination, and to use expensive equipment required for the circulation system or culture medium necessary for recycling the culture medium. It is not necessary to change the composition.
In addition, since the supply amount of the culture solution is adjusted based on the integrated amount of solar radiation, it is practically adjusted in consideration of the relationship between the amount of water absorption of the plant and the amount of solar radiation. The same management can be performed without largely changing settings.
Furthermore, as described above, when a medium having a high physical and chemical buffering capacity having a specific amount of readily available water, an ineffective water and a cation exchange capacity is used, such a medium is used. When the culture solution is supplied to the medium, the effect that the pH value and the electric conductivity (EC) of the solution in the medium are not easily changed is obtained.
[0008]
In the present invention, in the nutrient solution cultivation method, the amount of nitrogen supplied per individual plant is increased by an integrated solar radiation of 1 MJ / m. ² It is desirable that the amount is 2 mg or more and 8 mg or less, preferably 4 mg or more and 6 mg or less. As a method for supplying nitrogen, a fertilizer containing nitrogen may be added to the culture solution, the fertilizer may be directly added to the medium, or a combination of these may be used. The nitrogen form may be any form of inorganic nitrogen such as an ammonia form or a nitrate form, and it is desirable that the nitrate form is contained in 60% or more of the whole. Further, the nitrogen form may be a form of organic nitrogen such as an organic fertilizer, a fertilizer-controlled fertilizer, or a slow-release fertilizer. Usually, inorganic nitrogen is used by adding it to a culture solution in the form of a nitrogen fertilizer such as potassium nitrate, calcium nitrate, and ammonium phosphate. Organic nitrogen is usually used by directly adding an organic fertilizer or the like to a medium.
The addition ratio of fertilizers other than nitrogen, such as phosphorus, potassium, calcium, and magnesium, is preferably the most suitable for the crop, but is not particularly limited. The specific amount of nitrogen, phosphorus, potassium, calcium, etc. absorbed by the crop can be calculated from the composition of absorbed concentration in terms of weight (Vegetable Research Institute Research Data No. 21, Showa 61.11), and the ratio of N: P: K: Ca: Mg Is 10: 6.5: 16: 12: 5 for tomatoes, 10: 5.3: 13: 15.4: 5.3 for cucumber, and strawberry for N if N is 10. Is 10: 7: 16.7: 11.4: 3.4. Therefore, each fertilizer may be added according to the amount of absorption.
In the case of the cultivation method of the present invention, the supply amount of the culture solution is controlled by the integrated solar radiation amount, so that it substantially corresponds to the water absorption amount of the plant, so that the inorganic nitrogen supply amount is also supplied. It is desirable that the concentration is always constant with respect to the amount. For example, as shown in the examples below, in the results of a cultivation test of tomato, the water absorption of the tomato shows an integrated solar radiation of 1 MJ / m. ² Since the volume of the culture solution is about 70 ml per day, the amount of the culture solution supplied is 1 MJ / m of integrated solar radiation. ² It is sufficient to add about 6 to 6 mg of inorganic nitrogen per about 70 ml of the supplied liquid.
When a culture solution is supplied according to the nutrient solution cultivation method of the present invention, water corresponding to the amount of water absorbed by the plant is supplied. Are expected to accumulate or run short. As an effect of the present invention, by supplying a fertilizer of inorganic nitrogen as set above, a fertilizer can be supplied to a plant without excess or deficiency. In addition, by using the above-mentioned specific medium, it is possible to suppress and adjust the rapid fluctuation of the fertilizer concentration and composition in the solution in the medium by the chemical buffering action, and to adjust the element failure of the plant, such as nitrogen. The occurrence of deficiency and excess nitrogen can be avoided.
[0009]
As described above, the medium used in the cultivation method of controlling the liquid supply based on the integrated solar radiation according to the present invention has an easily available water content of 150 liter / m2. ³ Above, preferably 180 l / m ³ Above and the ineffective moisture content is 50 l / m ³ Above, preferably 70 l / m ³ A medium having a high physical and chemical buffering capacity and having a cation exchange capacity of at least 20 cmol / kg, preferably at least 30 cmol / kg is used.
Such a medium is composed of at least one kind of non-organic materials such as water purification plant generated soil, zeolite, vermiculite, perlite, charcoal, and general soil, and organic materials such as bark compost, peat moss, crushed coconut husk, and rice husk. A mixture obtained by mixing at least one of them can be obtained by measuring the amount of readily available water, the amount of ineffective water, and the cation exchange capacity, and selecting those having the above specific values. .
Preferred examples of the non-organic material used in the culture medium of the present invention include a water purification plant generated soil. The soil generated from the water purification plant is preferably a purified water cake obtained by concentrating and dewatering the sedimentary mud (purified sludge) generated during the water purification process. It is desirable that the soil generated from the water purification plant be subjected to a precipitation treatment by adding polyaluminum chloride or aluminum sulfate as a coagulant, and dewatered by a limeless treatment. In addition, the water content of the water generated from the water purification plant is adjusted to 40% by weight or more and 60% by weight or less, desirably 50% by weight or more and 55% by weight or less, and 50% by volume or more and 90% by volume or more are passed through a sieve having an opening of 2 mm. %, And what passes through a sieve having a mesh size of 10 mm and remains on a sieve having a mesh size of 2 mm preferably has a composition of 10% by volume or more and 50% by volume or less.
[0010]
When the water purification plant generated soil is used as the non-organic material, the water purification plant generated soil has a high phosphate absorption coefficient due to the effect of aluminum compounds added during the water purification process. It is preferred to add in an amount. Small amounts of phosphate fertilizer cause phosphate deficiency. On the other hand, when the amount of phosphoric acid added is large, the salt concentration in the soil is increased to cause damage to the roots, and excessive amounts of calcium, magnesium, and the like, which are subcomponents of the phosphate fertilizer, impair the mineral balance in the medium. In addition, since the cultivation period of plants belonging to fruit vegetables is long, it is desirable to continuously supply a phosphoric acid component to the plants. However, when supplying a liquid fertilizer containing phosphate fertilizer, the phosphate fertilizer must be prepared without causing phosphate deficiency at the start of cultivation, without increasing the electric conductivity of the culture medium, and without excess calcium or magnesium. It is desirable to use fertilizer. It is desirable that the phosphoric acid component contained be 20% by weight or more of the whole, and that the soluble phosphoric acid be 50% by weight or more. Examples of the type of phosphate fertilizer include molten phosphorus, magnesia perphosphoric acid, molten phosphorus fertilizer, heavy burnt phosphorus, molten phosphorus, Linster (registered trademark), Dublin (registered trademark), humus phosphorus, and the like. . The amount of the phosphate fertilizer to be added to the culture medium is desirably 1500 mg to 4000 mg, preferably 2000 mg to 3000 mg, as the phosphoric acid component per liter of the obtained medium.
Granulated water can be used as the water purification plant generated soil used in the medium of the present invention. The granulation method may be either a rolling granulation method or an extrusion granulation method. The usable particle size is 10 mm or less, preferably 8 mm or less.
[0011]
There are mainly three types of zeolites used as inorganic materials, one of non-organic materials: analcyme, mordenite, and clinoptinolite. In particular, mordenite and clinoptinolite have high cation exchange capacities and exchangeable cations. It has a high content and has the property of selectively adsorbing ammonium ions. Furthermore, as an effect of improving physical properties, it has the effect of increasing the water retention of soil, especially the amount of readily available moisture, and the permeability.For soil with low water retention such as sandy soil, it has the function of increasing water retention, so it is used for agriculture. Widely used. The most preferred zeolite is clinoptilolite, which has excellent effects for agricultural use. In the present invention, by adding zeolite to the medium, of the above-mentioned effects of the inorganic material, the water retention of the medium, particularly the easily available water content and the water permeability, are improved. Medium with high fertilizing ability and high buffer capacity can be obtained.
[0012]
Vermiculite used as an inorganic material, which is one of the non-organic materials, may be any commercially available soil improving material. Vermiculite is fired vermiculite at a high temperature and is a porous, light material. Also, the cation exchange capacity is high. For this reason, by adding vermiculite to the medium, it is possible to obtain a medium having a particularly high effective moisture content and improved water retention, and particularly a medium having a high fertilizing power and a high buffering capacity.
[0013]
Perlite used as an inorganic material, which is one of the non-organic materials, is obtained by crushing perlite and obsidian and firing at a high temperature, and has a high porosity and a light weight. In the present invention, any commercially available soil improver that enhances water retention, that is, increases the amount of easily and ineffectively water, and enhances water permeability may be used. By adding perlite to the medium, it is possible to obtain a medium having particularly improved water permeability and a high gas phase rate.
[0014]
The carbide used as an inorganic material, which is one of the non-organic materials, may be any material as long as it is commercially available as a soil amendment material.However, carbonaceous materials such as wood chips, rice husk, and food sludge are used as carbonaceous materials. Preferably, charcoal obtained by carbonizing wood chips and charcoal obtained by carbonizing rice husk are particularly desirable. In the present invention, by adding charcoal to the medium, the water permeability of the medium is particularly improved, and a medium having a particularly high gas phase rate can be obtained. In addition, since trace components such as various minerals contained in charcoal can be supplied to plants, it is possible to obtain a medium in which chemical properties are maintained for a long time.
[0015]
The general soil used as one of the non-organic materials refers to all the surrounding soils such as forest soil (black soil, red soil, masa soil, etc.), paddy soil, and field soil. These general soils have different effects on the characteristics of effective water content depending on the type, and have an agglomerated structure, such as andosol, upland soil, and red soil, paddy soil, and forest soil with high clay content. Can be expected to have an effect of increasing the effective moisture content of the easily-acting moisture content and the ineffective moisture content. Other effects such as Kanuma soil and sandy loam soil cannot be expected to increase the effective water content, but can be expected to increase the gas phase rate and water permeability.
[0016]
Bark compost can be used as one of the organic materials. The bark compost is particularly preferably used in combination with the soil generated from the water purification plant. By using bark compost, the medium can be softened and softened, and not only can the volume weight be light and easy to handle, but also a medium having an appropriate water retention can be obtained. In addition, the microbial flora grown during composting has the effect of increasing the biological buffering power of the medium. When bark compost is used, the amount used is preferably 30% by volume or more and 50% by volume or less based on the culture medium, and more preferably 35% by volume or more and 45% by volume or less. Bark compost is a bark of hardwood or conifer that has been fermented and ripened for a long time by adding a nitrogen source such as chicken manure or urea.It has been designated as a soil improvement material by government ordinance, and any commercially available product can be used. it can. The particle size of the bark compost is preferably 12 mm or less, more preferably 10 mm or less. Further, it is desirable that the bark compost has a C / N ratio of 35 or less, a total nitrogen content of 1.0% or more and 1.4% or less, and an electric conductivity of 1.0 dS / m or less. By using bark compost, especially fertilizer components contained in bark compost are eluted and supplied to the medium over a long period of time, and chemical buffering capacity is increased due to the influence of inorganic components and humic acid contained. Good medium chemistry can be maintained during the cultivation period. In addition, because it contains abundant carbon sources such as humus necessary for the activity of microorganisms, the microflora is activated, and when harmful pathogens enter the plants, competition and antagonism prevent the spread of pathogens and The labor of disinfection can be saved unless a disease occurs. The bark compost is desirably manufactured by fermenting the bark of conifers. Since the decomposition of hardwood is slow, the physical properties can be maintained even when used for a long period of time.
[0017]
Peat moss can be used as one of the organic materials. Peat moss has been designated by a government ordinance as a soil improvement material for the purpose of improving water retention, and any commercially available material may be used. Peat moss is particularly preferably used in combination with the water purification plant generated soil. By using peat moss, a medium having particularly high water retention can be obtained. The particle size of peat moss is preferably 12 mm or less, more preferably 10 mm or less. When peat moss is used, the amount used is preferably 5% by volume or more and 25% by volume or less, more preferably 10% by volume or more and 20% by volume or less based on the medium.
[0018]
Crushed coconut husks can be used as one of the organic materials. The crushed coconut husk is obtained by cutting the tissues of the pulp and wood of the palm. As described in JP-B-63-52848, JP-B-6-23, JP-A-1-313934, etc., the crushed coconut husk is used alone or by adding charcoal, fertilizer, etc. to retain water. It is used as a plant cultivation medium having a good balance of water permeability and fertilizer retention, and is generally marketed as a soil conditioner mainly for the purpose of improving water retention and fertilizing power. Depending on the degree of cutting, the crushed coconut husks may be as fine as powdery to as small as 3 cm in diameter. The crushed coconut shell used in the present invention preferably has a particle size of 2 mm or more and 12 mm or less. A crushed coconut husk having a particle size of 2 mm or less has a remarkably high water retention and causes poor water permeability, which is not preferable. On the other hand, when the thickness is 12 mm or more, the physical properties in the culture medium become uneven, which is not preferable. By using the crushed coconut husk as an organic material of the medium, it is possible to obtain a medium having a high gas phase rate and an improved water permeability of the medium.
[0019]
Rice husks can be used as one of the organic materials. Rice husk refers to the fibrous material of edible parts obtained when threshing rice. Since it has a structure that does not easily break down, the use of the medium as an organic material of the medium makes it possible to obtain a medium having a particularly high gas phase rate and improved water permeability. It is desirable that the used rice hulls have not been subjected to processing such as pulverization and have a well-maintained shape.
[0020]
The culture medium for nutrient cultivation used in the present invention is a mixture of at least one of the above-mentioned non-organic materials and organic materials, each of which is a mixture obtained by mixing at least one of them. , Preferably, the pH value, the electrical conductivity (EC) and the pF value are further measured, and those having the specific values described above are selected.
As a preferable combination of the non-organic material and the organic material, for example, a combination using a water purification plant generated soil, bark compost and / or peat moss, and further, if necessary, crushed coconut husk and / or rice husk, or water purification Combination of the soil generated from the field, at least one selected from zeolite, vermiculite, perlite, charcoal and general soil, with bark compost and / or peat moss, and optionally with crushed coconut husk and / or rice hull, etc. Can be In any case, it is preferable to use the soil generated from the water purification plant as one of the non-organic materials.
[0021]
The culture medium used in the present invention may contain an antagonistic microorganism having antagonistic properties to plant pathogenic bacteria. The microorganism is not particularly limited as long as it has antagonism to plant pathogenic bacteria, and any of bacteria, actinomycetes, fungi, and the like can be used. These microorganisms may be those obtained by cryopreservation or freeze-thaw of living cells as well as living cells. Further, two or more kinds of different kinds may be used simultaneously. The microorganisms may be spores obtained by individual culture, as well as those obtained by liquid culture. Examples of such antagonistic antibacterial agents include those described in Japanese Patent Publication No. 3-61424 and Japanese Patent Publication No. 3-61425. More specifically, Bacillus licheniformis, Thermoactinomyces sp, and Penicillium sp. Penicillium sp., Which have an antagonistic property against the soil-borne phytopathogenic fungus Fusarium spp. Aspergillus Terreus and Trichoderma Viride, which are antagonistic to the phytopathogenic bacterium Corticium rolfsii, and the like.
[0022]
When these bacteria are actually added, a culture solution of the bacteria may be added to the medium and mixed. The amount of antibacterial antibacterial added is 1m for nutriculture medium. ³ In general, the culture volume is 5 to 30 liters. When the bark compost is used as an organic material of the culture medium, the antibacterial antimicrobial may be added during the accumulation of the bark compost. In this case, the resulting culture medium for nutrient cultivation has a high microbial buffering power due to the addition of bark compost, and furthermore, by adding an antibacterial agent, even if blight germs are generated, it is controlled by the antagonism of the microorganisms. It is effective for In addition, as long as no disease occurs, the next crop can be planted without sterilization even after cultivation.
[0023]
In addition to the medium materials described above, a soil improving material that is generally used may be added mainly to adjust physical properties. The soil conditioner may be any material designated by a Cabinet Order for the purpose of improving physical properties, or any material commonly used as a raw material for a culture medium.
[0024]
In order to carry out the nutrient solution cultivation method of the present invention, for example, the culture medium is drained, the medium of the present invention is packed in a waterproof sheet bag, or a waterproof sheet having a length direction of about 100 to 120 cm. The cultivation is carried out by forming a cultivation bed including the medium of the present invention. The waterproof sheet is made of a material that does not allow water to pass through the roots, and may be a polyolefin (polyethylene, polypropylene) film, a fluorine-based film, a synthetic resin film, a root-proof sheet, a biodegradable plastic film, or the like. Alternatively, a fixed cultivation floor having a wide open upper end may be formed of plastic, steel, concrete, wood, or the like, and a culture medium may be filled in the fixed cultivation floor to form a cultivation floor.
The culture solution may be water or a solution obtained by adding a fertilizer component such as the above-mentioned inorganic nitrogen to water. Alternatively, a culture solution used for normal plant cultivation may be used. The culture solution is supplied to the culture medium by installing an irrigation tube of a drip or watering method in the installed cultivation bed and performing irrigation.
In the present invention, since the culture solution is supplied to the culture medium in accordance with the integrated solar radiation, the solar radiation sensor is usually set at an appropriate place where plant cultivation is performed, and the solar radiation is measured. The measured values are integrated by a counter, and when the set integrated value is reached, an irrigation tube or the like is set so that the supply of the culture solution starts. The supplied culture solution is measured by a flow meter, and set so as to supply a set constant culture solution to the medium. Commercially available products may be used for various measuring meters, devices, and the like used for controlling the liquid supply. In the present invention, by these liquid supply control, preferably, for a certain amount of solar radiation, the amount of water supplied to the plant after the growth stage is not influenced by the amount of growth, for plants after the growth stage, the culture liquid to be supplied per plant Change the amount of liquid supply to 1 MJ / m ² The amount of waste liquid of the culture solution discharged out of the medium system by adjusting the supply amount per unit is adjusted to 15% or less, preferably 10% or less, particularly preferably 5% or less of the supply amount. In the present invention, the supply amount of the culture solution to be supplied per one plant is usually controlled by the above-described supply control device, and the integrated solar radiation amount is 1 MJ / m. ² By setting the volume per culture to 40 ml to 200 ml, the waste liquid rate of the culture solution discharged out of the medium system can be adjusted to 15% or less, preferably 10% or less, particularly preferably 5% or less of the supplied amount.
In addition, for example, an appropriate amount of fertilizer containing inorganic nitrogen is added to the culture solution, and the amount of inorganic nitrogen supplied per plant is similarly increased to an integrated solar radiation of 1 MJ / m2. ² It can be set to be 2 mg or more per mg.
In plant cultivation, when a culture solution is supplied to a culture medium, the pH value of the solution in the culture medium is in the range of 5.0 to 7.5, particularly in the range of 5.5 to 7.0, The degree (EC) (dS / m) is preferably set to be in the range of 0.8 to 2.5 dS / m, particularly 1.5 to 2.0 dS / m. Furthermore, when the pF value is usually in the range of 1.5 to 3.2, and particularly when the yield is to be prioritized over the quality, the pF value is preferably from 1.5 to 2.4. For example, in the case of tomatoes, when it is desired to take those having a sugar content of 6.5 or more, it is preferable to set the range so as to be in the range of 2.4 to 3.2. In the present invention, as described above, since a medium having a high physical and chemical buffering power having a specific amount of readily available water, an ineffective water, and a cation exchange capacity is used, such settings are compared. It can be done easily.
[0025]
【Example】
The present invention will be described in more detail based on the following examples, but the present invention is not limited to these examples.
Example 1
The following tests were conducted to determine the proper culture medium characteristics in the liquid supply management based on the solar radiation proportional method based on the accumulated solar radiation.
(1) Test method
The test plant is a tomato 'House Momotaro', the seedlings that cotyledons are developed, potted in a No. 3 pot packed with horticultural culture soil, and when 6 to 7 true leaves are developed, planted in a cultivation bag, Pinching was performed except for the upper two leaves of the 4-stage fruit cluster. As for the liquid supply management method, a sufficient liquid supply was performed by a timer method from the planting to the second week to promote root survival. After that, in all treatment areas, as shown in Table 1, the integrated solar radiation amount was 1 MJ / m ² The amount of the culture solution supplied per unit was adjusted so that the average waste liquid rate during the cultivation period of the culture solution from the medium was 10% or less of the supply amount. The culture solution used was a garden test formulation, and the concentration was adjusted to 1/2 times the standard (specific composition was N: 8, P: 2, K: 8, Ca: 4, Mg : 2me / l). As shown in Table 1, the test medium had a composition in which the mixing ratio of peat moss and water purification plant generated soil was changed in order to change the water retention characteristics. The peat moss uses the adjusted peat. The soil generated from the water treatment plant is generated from the water treatment plant, and for about three months, the compost made by sedimentation and cutting is adjusted with a sieve with an opening of 8 mm, and the phosphate fertilizer is further purified. 2000 mg of phosphoric acid was added per liter of generated soil. In addition, tests using rock wool, rice husk charcoal, and peat moss as the medium were performed in the same manner. Each treatment medium was packed in a plastic film bag for 10 liters, shaped so that the height of the bag was about 15 cm, and placed on a foamed styrene bed. The styrofoam cultivation bed was designed to collect waste liquid from the bag. For planting, two plants were planted per bag.
Investigation items were determined as the water-retaining properties of the test medium, such as the amount of readily available water and the amount of ineffective water, and the pH and electric conductivity (EC) of the medium at the end of cultivation were measured. Plant surveys measured growth and yield.
[0026]
[Table 1]

[0027]
(2) Test results
Table 2 shows the effective water content and cation exchange capacity (CEC) of the medium. As the proportion of soil generated from the water treatment plant increased, the amount of readily available moisture gradually decreased, and the amount of ineffective moisture increased. The CEC increased with an increase in the mixing ratio of the soil generated from the water treatment plant, and was 10 cmol / kg or less for rock wool, rice grain charcoal, and peat moss.
[0028]
[Table 2]

[0029]
Table 3 shows the pH and EC of the medium at the end of cultivation. The pH was as high as 8.5 or more in the 10 and 20% by volume sections, and 5 to 7 in the 30 to 80% by volume section. Rock wool and charcoal were as high as 8 or more, and peat moss was as low as 5 or less. Regarding EC, 10 and 20% by volume were significantly higher than those of other zones, and decreased as the mixing ratio of water purification plant generated soil was increased. And peat moss showed a high value of 3-5.
[0030]
[Table 3]

[0031]
Table 4 shows the above-ground live weight and yield. The live weight of the leaves and stems increased as the mixing ratio of the water purification plant generated soil increased from the 10% by volume section, and 500 g or more in the 30 to 60% by volume section. The yield was remarkably higher in the 40, 50, and 60% by volume groups than in the 10, 20, 30, 70, and 80% by volume groups, showing around 3000 g per plant, whereas in rock wool, rice husk charcoal and peat moss, 2000 g. Before and after.
[0032]
[Table 4]

[0033]
From the above, the integrated solar radiation 1MJ / m ² When the nutrient solution is cultivated by controlling the supply amount of the culture solution per unit so as to control the liquid supply so that the waste liquid rate is 10% or less, the medium used has an easily available water content of 150 l / m 2. ³ As described above, the ineffective moisture content is 50 liters / m. ³ As described above, it has been found that the cation exchange capacity (CEC) is desirably 20 cmol / kg or more.
[0034]
Example 2
In this example, an appropriate cation exchange capacity was examined as a culture medium used in a cultivation method in which liquid supply was controlled by a solar radiation proportional method.
(1) Test method
The test plant used was tomato 'House Momotaro', and the cultivation method was the same as in Example 1. As for the liquid supply management method, as in Example 1, sufficient liquid supply was performed by the timer method from the planting until the second week, and roots were encouraged. After that, it was transplanted to each treatment section shown in Table 5, and as shown in Table 6, the integrated solar radiation amount was 1 MJ / m ² The amount of the culture solution supplied per unit was adjusted so that the average waste liquid rate during the cultivation period of the culture solution from the medium was 10% or less of the supply amount. The culture solution used was a garden test formulation, and the concentration was adjusted to 1/2 times the standard (specific composition was N: 8, P: 2, K: 8, Ca: 4, Mg : 2me / l). The test medium was prepared by mixing red soil with 20% by volume of adjusted peat moss, and the effective water content was 185 liters / m. ³ With ineffective moisture content of 80 l / m ³ Met. As shown in Table 5, in the treatment group, 7 types of media having different cation exchange capacities were prepared by adding 2 g of zeolite per liter of the media to the prepared media.
The survey items were the cation exchange capacity of the test medium, the amount of ineffective water and the amount of readily available water, the pH and EC of the solution in the medium during the cultivation period, and the yield and the occurrence of malformed fruit for plants.
[0035]
[Table 5]

[0036]
[Table 6]

[0037]
(2) Test results
The obtained results are shown in Tables 7, 8 and 9.
As can be seen from Table 7, the pH of the solution in the culture medium during the cultivation period increased with the passage of time in the 2 and 4 g sections, and became 8.0 or more two months after planting, and the added amount of zeolite was 6 g or more. In the section No., the value was 6.0 to 7.0.
[0038]
[Table 7]

[0039]
As can be seen from Table 8, the EC of the solution in the medium in 2 g and 4 g groups showed a sharp increase with time after planting and became 3.5 dS / m or more after 2 months. On the other hand, in the section where the amount of zeolite added was 6 g or more, 1.0 to 2.0 dS / m was exhibited.
[0040]
[Table 8]

[0041]
As can be seen from Table 9, the yield was lower in the 2 g and 4 g sections than in the other sections, significantly higher in the section where the amount of zeolite added was 6 g or more, and was higher than 3000 g in the section where the amount of zeolite added was greater than 10 g. The percentage of malformed fruits with respect to the total harvested number was higher in the sections 2 and 4 g than in the other sections, and markedly decreased to 10% or less in the section where the amount of zeolite added was 6 g or more.
[0042]
[Table 9]

[0043]
From the above, when the liquid supply is controlled so that the waste liquid rate is 10% or less based on the integrated solar radiation, the CEC of the medium to be used should be 20 cmol / kg or more, preferably 30 cmol / kg or more. Turned out to be desirable.
[0044]
Example 3
In this example, when the liquid supply was managed based on the integrated amount of solar radiation, the effect of the difference in the waste liquid rate on the yield and quality of tomato was investigated.
(1) Test method
The test plant is a tomato 'House Momotaro', the seedlings that cotyledons are developed, potted in a No. 3 pot packed with horticultural culture soil, and when 6 to 7 true leaves are developed, planted in a cultivation bag, Pinching was performed except for the upper two leaves of the 4-stage fruit cluster. As a liquid supply management method, an insolation proportional method based on the integrated amount of insolation and a timer method as a comparative example were adopted. In the solar radiation proportional method, in order to change the waste liquid ratio with respect to the supply amount of the culture liquid discharged from the culture medium, as shown in Table 10, the integrated solar radiation amount was 1 MJ / m. ³ The liquid supply amount per unit was set to 12 levels of 20 to 240 ml, and the timer system was set so that 20% of the liquid supply amount was drained. The same culture solution as in Example 1 was used. The medium to be used is a mixture of peat moss: bark compost: water purification plant generated soil mixed at a volume ratio of 3: 3: 4. Adjustment of peat moss and water purification plant generated soil is performed according to Example 1, and bark compost is used. Used was a conifer aged as a raw material and passed through an 8 mm sieve. The prepared medium had an easily accessible water content of 152 l / m2. ³ With ineffective water content of 82 l / m ³ , CEC was 22 cmol / kg. From the planting to two weeks after the planting, only water was supplied, and thereafter, a culture solution having a concentration 1/2 times that of the garden test formulation was supplied (specific compositions were N: 8, P: 2, and K: 8, Ca: 4, Mg: 2me / l).
The survey items were the water state in the medium during the cultivation period and the waste liquid ratio with respect to the amount of liquid supplied, and the water state in the medium was measured using a ceramic soil moisture meter. For plants, Brix sugar content and incidence of physiological disorders were used as indicators of yield and quality.
[0045]
[Table 10]

[0046]
(2) Test results
The obtained results are shown in Tables 11, 12 and 13.
As can be seen from Table 11, the waste liquid rate is 0 in the 80 ml section, and in the section where the liquid supply amount is larger than the 100 ml section, it gradually increases with the increase in the liquid supply amount. It showed 25 to 35% or more.
[0047]
[Table 11]

[0048]
As can be seen from Table 12, the EC of the solution in the culture medium showed 8 or more in the 20 to 60 ml section, and gradually decreased as the amount of liquid supplied increased. The pF value was 3 to 3.5 in the 20 to 60 ml section, gradually decreased as the supply amount increased, and became saturated with the supply amount in the 220 and 240 ml sections and 1.5 or less in the timer method.
[0049]
[Table 12]

[0050]
Table 13 shows the yield and quality of tomato. The yield increased with an increase in the liquid supply amount up to the 200 ml section, decreased in the section with a larger liquid supply amount, and was lower in the sections below 40 ml and above 220 ml section as compared with the timer method. The Brix sugar content decreased as the amount of liquid supplied increased, and was 6.0 or more in the 200 ml or less section, but rapidly decreased to 5 or less in the 220 and 240 ml sections. Regarding the physiological disorders, the butt rot fruit tended to occur when the liquid supply amount was small, and gradually decreased with an increase in the liquid supply amount, and the occurrence rate was 0% in 140 ml or more. On the contrary, the cracking rate was high in the section where the amount of liquid supplied was large, and was 0 in the section of 160 ml or less, but increased as the amount of liquid supplied increased in the section of 180 ml or more, and sharply increased in the section of 220 ml or more.
[0051]
[Table 13]

[0052]
From the above, when the liquid supply is controlled based on the accumulated solar radiation, the yield and quality of tomatoes are greatly affected by the liquid supply amount, and when the liquid supply amount is 40 ml or less, the plants receive extreme water stress and the sugar content increases. However, ass rot fruit was frequent and the yield decreased. On the other hand, when the amount of liquid supplied was extremely large, the inside of the medium was in a humid condition, and cracking occurred frequently. From this, when tomato is cultivated by liquid supply control based on the integrated amount of solar radiation, the amount of culture solution supplied per strain (one individual) is calculated as the daily insolation of 1 MJ / m2. ² It has been found that it is desirable to set the waste liquid rate to 15% or less by setting the waste liquid rate to 60 ml or more per 200 ml.
[0053]
Example 4
In the present embodiment, an appropriate nitrogen supply amount when the liquid supply was controlled by the solar radiation proportional method was examined.
(1) Test method
The test plants used were solanaceae tomato, cucumber cucumber, and rosaceae strawberry. The test medium used was a mixture of peat moss, bark compost, and soil from a water purification plant in a volume ratio of 3: 3: 4. The adjustment of the individual materials was in accordance with Example 1. The effective water content of the test medium is 168 l / m. ³ , 90 l / m ³ , CEC was 20 cmol / kg. The cultivation method was the same as in Examples 1 and 2 for tomato. The cucumber used was Hogi 'Sharp 301' as the test variety, and 'Yuyu Ikki' was used as the rootstock, and the arbor was 16-node pinching of the main branch, 1-node pinching of the primary side branch, leaving the secondary side branch and beyond. Strawberries were planted in early September and harvested from January to May, using 'Onmine' as a test variety.
The culture solution was based on the garden test formulation. Further, as shown in Table 14, the amount of added nitrogen in the culture solution was varied in each treatment group. The amount of added nitrogen is adjusted by adjusting the amount of potassium nitrate and calcium nitrate. Other fertilizer compositions (P: K: Ca: Mg composition of tomato: 2: 4: 3: 2me / l, cucumber: 3 (6: 7: 4 me / l, in the case of strawberry, 1: 5: 3: 2: 1 me / l) was adjusted so as to be equal in each processing section.
The survey items were the supply amount and waste liquid rate during the cultivation period, the yield of tomato, cucumber and strawberry, nitrogen deficiency and excess, and EC of the medium solution during the cultivation period.
[0054]
[Table 14]

[0055]
(2) Test results
The obtained results are shown in Tables 15, 16 and 17.
As can be seen from Table 15, the EC of the solution in the culture medium at the time of harvest increased with an increase in the amount of added nitrogen, regardless of the type of the test plant. Nitrogen was added at 2 mg for tomato and 4 mg or less for cucumber, which was 0.5 dS / m or less, which was below the appropriate range. In the high-concentration range, the tomato content was 7 mg or more, the cucumber content was 9 mg or more, and the strawberry content was 7 mg or more, which was 3.0 dS / m or more.
[0056]
[Table 15]

[0057]
As can be seen from Table 16, tomatoes increased from the 1 mg section with an increase in the amount of added nitrogen, and rapidly decreased with an increase in the addition amount from the 6 mg section, and the yield was higher than that of the timer method in the range of 4 mg to 6 mg. It was below. Cucumber increased from the 1 mg section with an increase in the amount of nitrogen added, gradually decreased at the peak of the 8 mg section, and the yield was higher than that of the timer method in the range of 4 mg to 8 mg. Strawberries increased from the 1 mg section with an increase in the amount of nitrogen added, gradually decreased at the 4 mg section, and the yield was higher in the 2 mg to 5 mg section compared to the timer method.
[0058]
[Table 16]

[0059]
Table 17 shows the results of visual judgment of nitrogen deficiency and excess disease of the test plants. Deficiency was defined as deficiency in which yellowing of the lower leaves was observed, and deficiency was defined as a decrease in yield due to excessive vegetative growth under nitrogen-rich nutrition. As a result, deficiency was observed at 3 mg or less for tomato, 2 mg or less for cucumber, and 1 mg or less for strawberry. Excessive illness was observed at 8 mg or more for tomato, 9 mg or more for cucumber, and 7 mg or more for strawberry.
[0060]
[Table 17]

[0061]
From the above, the amount of inorganic nitrogen in the culture solution per one strain (one individual) was calculated as the integrated solar radiation amount of 1 MJ / m ² It has been found that it is preferable to control the liquid supply at a rate of 2 mg or more and 8 mg or less, and it is particularly preferable to control the liquid supply at 4 mg or more and 6 mg or less.
[0062]
【The invention's effect】
As is clear from the above results, according to the present invention, the medium has an easily available water content of 150 liter / m 2. ³ As described above, the ineffective moisture content is 50 liters / m. ³ Using a medium having a high cation exchange capacity of at least 20 cmol / kg and having a high physical and chemical buffering capacity, the amount of culture solution supplied per plant is determined by the integrated solar radiation amount of 1 MJ / m. ² The plant is extremely efficiently and satisfactorily controlled by adjusting the supply amount per unit so that the waste liquid ratio of the culture solution discharged out of the medium system is adjusted to 15% or less of the supply amount and controlling the supply. Can be cultivated. By the nutrient solution cultivation method, the amount of waste liquid of the culture solution discharged out of the culture medium is suppressed as much as possible, and it is possible to manage the liquid supply corresponding to the water absorption of the plant to adjust the amount of liquid supply based on the integrated amount of solar radiation. Become. Furthermore, in the nutrient solution cultivation method, the amount of inorganic nitrogen supplied per plant is calculated by integrating the amount of solar radiation to 1 MJ / m 2. ² When the amount is 2 mg or more and 8 mg or less per day, the fertilizer can be supplied to the plant without excess or deficiency, and for example, occurrence of nitrogen deficiency, excess nitrogen, and the like can be avoided.

Claims

In a nutrient solution cultivation method in which plants are cultivated on a solid medium isolated from the ground and the liquid supply is managed in a solar radiation proportional method based on the integrated solar radiation,
As a solid medium, use is made of a solid medium having an effective water content of 150 l / m ³ or more, an ineffective water content of 50 l / m ³ or more, and a cation exchange capacity of 20 cmol / kg or more,
The amount of culture solution supplied per individual plant is adjusted by the amount supplied per 1 MJ / m ^{2 of} integrated solar radiation, and the waste liquid rate of the culture solution discharged outside the culture system is 15% of the supplied amount. Control the liquid supply so that
A method for cultivating a plant with nutrient solution.

The amount of the culture solution supplied per plant is set to 40 ml to 200 ml per 1 MJ / m ^{2 of} integrated solar radiation, and the waste liquid rate of the culture solution discharged outside the culture system is set to 15% or less of the supply amount. The method for hydroponics according to claim 1.

The method for hydroponics according to claim 1 or 2, wherein the amount of nitrogen supplied per plant is ² mg or more and 8 mg or less per 1 MJ / m2 of integrated solar radiation.

As a solid medium, at least one non-organic material selected from water purification plant generated soil, zeolite, vermiculite, perlite, carbide and general soil, and at least one organic material selected from bark compost, peat moss, crushed coconut husk and rice husk The method for hydroponics according to any one of claims 1 to 3, wherein a mixture of materials is used.

The method according to any one of claims 1 to 4, wherein the plant is a tomato, eggplant, cucumber or strawberry.