JP3992939B2 - Irrigation control device for rooftop and aboveground greening system - Google Patents

Description

【００２６】
により誘電率Ｋａが求められる。上式において、ｒ₁ とｒ₂ は信号電極と遮断電極の半径であり、Ｆは形状因子である。求められた土壌の比誘電率Ｋａから次式：
θ=-5.3 ×10^-2+2.92 ×10^-2Ka-5.5×10^-4Ka²+4.3 ×10^-6Ka³
の経験式によって、体積含水率θ（ｍ³ ・ｍ^-3）を求めめることができる。
なお、電圧定在波の振幅は、土壌水分が多くなる（比誘電率が大きくなる）と小さくなる特性をもつ。この場合、その土壌の含水量を別に重量法などにより測定しておき、ＡＤＲ法などで測定を行ってその出力信号値（例えば出力電圧）を求め、前記の土壌の含水量を変化させて測定を繰り返せば、土壌の含水量からの体積含水率と出力電圧との較正された関係線を得ることができ、現場でのＡＤＲ法による測定で土壌の正確な体積含水率を得る手段が得られる。
このようにして、ＡＤＲ法などの誘電率に基づく方法により土壌の体積含水率を求めることができる。ＡＤＲ法におけるセンサーの出力電圧と体積含水率θとの関係を図２に示す。両者に相関関係があることが分かる。
【００２７】
上記したように、誘電率に基づく方法、特にＡＤＲ法によれば、簡単かつ容易に土壌の体積含水率を求めることができ、しかもＡＤＲ法では、ある直径の円筒上部分の土壌の平均誘電率の測定に基づいているので、センサーのプローブが土壌の粒子に密着していなくてもよく、軽石粒子などのような粒子の粗い土壌についても体積含水率を測定できるという利点がある。なお、上記並びに下記においては、ＡＤＲ計によって電圧を出力させてこれに基づいて体積含水率を求める方法を説明しているが、本発明方法においては、ＡＤＲ計による他の出力信号値に基づいて体積含水率を求めてもよいし、或いはＴＤＲ計やＦＤＲ計のような他の形式のセンサーの出力信号値に基づいて体積含水率を求めてもよい。
【００２８】
しかしながら、このような測定で得られる土壌の体積含水率、つまり含水量は、土壌の結合水などの植物に利用できない水の量も含んでいるので、植物に利用し得る水の量と良く対応しているｐＦ値とは異なっている。
本発明においては、このようにしてＡＤＲ法などにより得られる土壌の体積含水率の測定結果を、土壌のｐＦ値に換算することによって、土壌のｐＦ値を求める。
【００２９】
土壌試料のマトリクスポテンシャル（ｐＦ値）と体積水分率とは、その土性に依存して特有の相関関係があり、これを水分保持曲線と呼ぶ。土壌試料の水分保持曲線、即ちマトリクスポテンシャルと体積水分率との相関関係を測定する方法としては、砂柱法、吸引法、加圧板法、加圧膜法などが知られている。これらの方法のうち、砂柱法を除く他の方法はいずれも、所定の圧力を土壌試料にかけて平衡状態に達した際の土の重量を測定することにより、そのマトリクスポテンシャルに対応する体積含水率を求め、これを種々の圧力において行うことにより、その土壌試料についての水分保持曲線を得るというものである。また、砂柱法は、土壌試料に圧力をかける代わりに、砂柱上に載置された土壌試料に所定の位置ポテンシャルを与えることによって、同様の測定を行うものである。
【００３０】
本発明においては、このように、土壌の体積含水率とｐＦ値との間に土性に依存する相関関係が存在することに着目し、測定対象の土壌について予め水分保持曲線（相関線）を求めておき、上記のＡＤＲ法などの方法によって求められた土壌の体積含水率の値から、相関線によりその土壌のｐＦ値を求める。なお、相関線は、表としたときには換算表に基づいてもよいし、可能であれば近似式としてもよい。相関線によって土壌の体積含水率の値から土壌のｐＦ値を求める手段としては、例えば、予め求めた相関線を組み込んだ演算装置にＡＤＲ計の出力信号を入力して土壌のｐＦ値に対応する信号を出力するというプログラムを組み込んだマイコンなどの演算装置を利用する手段を用いることが好ましいい。
【００３１】
以下において、土壌について、体積含水率とｐＦ値との相関を調べて関係線を作り、誘電率に基づいてその土壌の体積含水率を求め、作成された関係線に基づいて、求められた体積含水率から土壌のｐＦ値を求める本発明に係る手法について説明する。
まず、体積含水率とｐＦ値との関係線（水分保持曲線）を作るための基礎データとなる。土壌の種々の体積含水率に対応するｐＦ値を、当該技術において公知の方法により求める。ｐＦ値の測定は正確性が必要であるから、室内で行う測定法を採用する。公知の室内で行うｐＦ値測定法としては、砂柱法、加圧板法、吸引法、加圧膜法、蒸気圧法を挙げることができる。この中で、砂柱法はｐＦ値が０．５〜１．４の範囲、加圧板法はｐＦ値が１．６〜２．７の範囲の測定に適しているといわれている。また、ｐＦ値の測定方法として「遠心法」という方法も提案されているが、この方法はまだ十分に実用化されていない。したがって、ｐＦ＝１．７〜２．７の易効水の範囲内に土壌の含水量を保つという本発明の目的に合致する方法としては、加圧板法が最も適しているということができる。しかしながら、砂柱法などの他の方法も本発明において用いることができる。
【００３２】
例えば、加圧板法により土壌のｐＦ値を測定する場合には、次のように行う。
まず、図４を用いて加圧板法の技術内容について簡単に説明する。加圧板装置１０は加圧チャンバー１２と加圧板１３で構成されており、加圧板１３は素焼板１４の下側にスクリーン１５をはさみ、それをゴム膜１６で覆う構造になっている。加圧チャンバー１２には圧力ゲージ１８が設けられていて、チャンバー内の空気圧が読み取られる。
水で飽和した素焼板１４の上に土壌試料１１を載せ、加圧装置連通管１７から空気圧を加えると、その空気圧と平衡するマトリックスポテンシャルより大きいポテンシャルで保持されている土壌水は素焼板１４を通して排水される。土壌水は金属製排水孔１９から耐圧チューブ２０、排水口２１を通り、ピンチコック２２を有する排水チューブ２３から排水ビン２４に入る。加圧チャンバー１２の減圧のために排気バルブ２５を設ける。空気圧を段階的に変えることにより、各マトリックスポテンシャルに対応した水分保持量を測定できる。サンプルの土壌は、その空気圧の大きさ毎に、加圧板ごと取り出して計量する。この測定された土壌試料の重量と乾燥状態の土壌試料の重量との差を算出することによって、含水量が求められる。ここで求められた含水量は、そのときの空気圧に対応するもの、すなわちその時の水分ポテンシャルに対応するものであるから、あるｐＦ値に対応する含水量が求められる。また、土壌の嵩比重に基づいて、体積含水率も求められることになる。
この操作を、空気圧を段階的に変えて繰り返して行うことにより、種々のｐＦ値とそれに対応する体積含水率との対比表が作成される。表の値を、横軸がｐＦ値、縦軸が体積含水率のグラフにプロットすると、水分保持曲線が得られる。
【００３３】
また、同様に土壌のｐＦ値を測定する方法である砂柱法の原理を図５を参照して説明する。
図５は、砂柱法装置５１の概要を示す図である。通常、２５０μｍ以下のふるいを通過した細砂や３００〜１８０μｍに粒径を調整した石英砂が用いられる。事前に水洗いした砂５２をカラムに充填し、コック６０を開放して給水口５９から水道水５８を流入させて、砂を水で飽和させる。なお、カラムの底部には支持台６１及びブラススクリーン６２が配置されて、砂柱を保持するようになっている。そして、周囲をたたくなどして振動を与え、粒子配列を安定させる。砂柱上面からの蒸発を防ぐために、ポリエチレンシート又は蓋５３をかぶせておく。彩土円筒５４にも蓋をつけておくと更に効果的である。土壌試料（彩土円筒）５４を砂柱５２の上に載置し、可動式の排水口５５の高さを砂柱上端に固定して、土壌試料５４へ水を飽和させる。次に、可動排水口５５を所定の位置まで下げ、コック５６を開放して余剰水５７を排水することによって、砂柱中の自由水面の水位を下げ、これにより土壌試料からの脱水を行わせる。水位Ｌは水位計６３によって読取る。脱水が完了したらその時の土壌試料の質量を測定して、体積含水率を求める。この時点での、土壌試料のマトリクスポテンシャル（ｃｍ）は、土壌試料の厚さを１とすると、−（Ｌ＋１／２）で示される。これにより、所定のｐＦ値における土壌試料の体積含水率が求められる。
【００３４】
この操作を、水位Ｌを段階的に変えて繰り返して行うことにより、種々のｐＦ値とそれに対応する体積含水率との対比表が作成される。表の値を、横軸がｐＦ値、縦軸が体積含水率のグラフにプロットすると、水分保持曲線が得られる。
【００３５】
一方、同じ土壌について、体積含水率の分かったサンプルに関して例えばＡＤＲ計でその出力信号値、例えば出力電圧を測定して、出力電圧と土壌の体積含水率との較正された換算表を作成する。この結果を、横軸が出力電圧、縦軸が体積含水率のグラフにプロットすると、図３のような関係線が得られる。
【００３６】
このように予め関係線を作成しておき、一般圃場の現場で例えばＡＤＲ計を用いて土壌の含水量を測定すると、第１の工程として、ＡＤＲ計の出力電圧から、予め作成された出力電圧と体積含水率との関係線に基づいて土壌の体積含水率が求められ、次に第２の工程として、求められた土壌の体積含水率から、予め作成された水分保持曲線（体積含水率とｐＦ値との関係線）に基づいて土壌のｐＦ値を求めることができる。
前記した２つの関係線を演算装置へ入れておけば、電子回路を用いてＡＤＲ計の出力電圧の信号からその土壌のｐＦ値を演算してその数値をディスプレイに表示することができ、測定作業が極めて簡便となる。
あるいはさらに、その演算で得た土壌のｐＦ値の信号を灌水装置の制御回路に送り、灌水装置の給水装置を作動させるようにすることもできる。
【００３７】
本発明の方法によれば、従来用いられていたテンシオメータ法に比べて、遙かに簡便に土壌のｐＦ値を直接且つ連続的に測定することができ、この測定結果を利用して灌水制御を行うことができる。また、テンシオメータ法では、軽石等のような多孔質表面を持つ粗い粒子からなる培地についてはｐＦ値の測定を行うことができなかったが、本発明方法によれば、ＡＤＲ法などのような多孔質培地にも適用可能な方法によって体積含水率の測定を行うことにより、ｐＦ値を求めることができる。
【００３８】
なお、本発明においてｐＦ値と体積含水率との相関（水分保持曲線）を測定する方法として使用される加圧板法や砂柱法などによっては、特殊な土壌や培地、特に多孔質表面を有する粒子からなる土壌（培地）を測定することができない。これは、例えば培地として粒径が１〜５．６ｍｍの軽石を使用した場合、加圧板法では、粒子間に圧力をかけても含有水が連続していないために正確なｐＦ値を測定することができないからである。即ち、軽石粒子培地などでは含有水が連続して存在していないために、毛管現象の毛管水がつながらないので正しいｐＦ値を測定することができない。また、砂柱法では、軽石培地の場合、水の液絡がないので、正確なｐＦ値を測定することができない。そこで、本発明方法によって、多孔質表面を有する粒子からなる土壌についてｐＦ値の測定を行う場合には、更なる工夫が必要となる。以下、この点について詳しく説明する。
【００３９】
本発明者らは、加圧板法や砂柱法によって、軽石培地のｐＦ値を測定することができないかどうかを検討したところ、粗い培地粒子のみの試料ではｐＦ値の正確な測定はできないが、粗い培地粒子に細かい培地粒子を混合したものについてはそのｐＦ値を測定できることが分かった。そして、粗い培地粒子の土壌試料と、当該培地試料を粉砕して作成した培地微粒子試料とを用意し、更に、粗い培地粒子の土壌試料と培地微粒子試料とを混合して分散させた混合土壌試料を用意し、この培地微粒子試料と混合土壌試料とについてｐＦ値の測定を行い、得られた結果を以下に説明する「減算処理」にかけることにより、粗い培地粒子の土壌試料のｐＦ値を求めることができることを見出した。以下において、この方法に関して詳細に説明する。
【００４０】
まず、粗い培地、例えば粒径１〜５．６ｍｍの軽石粗粒子からなる培地を用意する。次に、この粗粒子培地を粉砕して微粒子とした培地微粒子を調製する。また、上記の軽石粗粒子と培地微粒子とを混合して分散させた混合土壌試料を調製する。この場合、軽石粗粒子と培地微粒子とは、等重量ずつ混合することが好ましいが、必ずしも等重量である必要はない。但し、その場合には混合重量比を確認する。
【００４１】
このようにして得られた培地微粒子試料と混合土壌試料について、加圧板法などの方法によってｐＦ値と体積含水率との関係、即ち水分保持曲線を求める。この方法について以下に説明する。以下の説明においては、便宜上、軽石粗粒子培地試料を試料Ｂ、軽石粗粒子から調製した培地微粒子試料を試料Ａ、試料Ａと試料Ｂとを混合して得られた混合土壌試料を試料Ｃと呼び、加圧板法によるｐＦ値測定を例として挙げる。
【００４２】
培地微粉末からなる試料Ａは加圧板法によりｐＦ値を測定することができるが、軽石粗粒子試料Ｂは加圧法によりｐＦ値を測定することができない。しかしながら、混合土壌試料ＣについてはｐＦ値を測定することができる。これは、粗い粒子の間隙に細かい微粒子が入り込むことにより、ブロースルーが起きないためであると考えられる。したがって、混合土壌試料の調製に用いる培地微粒子試料の粒径は、微粒子が粗粒子の間隙に入り込むようなものであることが望ましい。更には、微粒子が多孔質粗粒子の孔に入り込まない程度の大きさである必要がある。これは、微粒子が多孔質粗粒子の孔に入り込んでしまうと、挙動が変化してしまい、正確なｐＦ値を計測することができなくなってしまうからである。一般に微粒子試料の粒径は、５０〜２００μｍ程度であることが好ましいが、この数値に限定されるものではない。
【００４３】
上述のように、粗粒子試料ＢについてはｐＦ値の測定を行うことができないが、微粒子試料Ａ及び混合土壌試料ＣについてはｐＦ値の測定を行うことができる。そこで、混合土壌試料Ｃについての測定結果と微粒子試料Ａについての測定結果から、試料Ｂについての測定結果を以下に説明する「減算処理」によって求める。
混合土壌試料Ｃ及び微粒子試料Ａについて、加圧板法により、ｐＦ値と体積含水率との関係、即ち水分保持曲線を測定する。これらの測定は、各試料の含水状態を変えて幾通りにも測定する。
【００４４】
あるｐＦ値における混合土壌試料Ｃの体積含水率をｘ_c （ｖ／ｖ％）、所定容量の混合土壌試料の含水量をｃ（ｇ）とすると、その混合土壌試料のうち微粒子が保持する水の量［ｃ_a （ｇ）］は、同じ容量の培地微粒子試料ＡがそのｐＦ値において有する含水量［ａ（ｇ）］に、混合土壌試料中の培地微粒子の重量割合を乗じた値となる。即ち、上記所定容量の混合土壌試料中の培地微粒子の重量をｚ_ca（ｇ）、同容量の培地微粒子試料の重量をｚ_a （ｇ）とすると、ｃ_a ＝ａ×（ｚ_ca／ｚ_a ）となる。次に、混合土壌試料Ｃの含水量［ｃ（ｇ）］から混合土壌試料中の培地微粒子が保持する水の量［ｃ_a （ｇ）］を減じれば、混合土壌試料Ｃ中の粗粒子が保持する水の量［ｃ_b （ｇ）］が求められる。即ち、ｃ_b ＝ｃ−ｃ_a となる。そして、この水の量を、混合試料における粗い培地の割合で割ると、粗粒子培地試料Ｂの含水量を算出することができる。即ち、同容量の粗粒子培地試料Ｂの重量をｚ_b （ｇ）、粗粒子培地試料Ｂの含水量をｂ（ｇ）とすると、ｂ＝ｃ×（ｚ_b ／ｚ_cb）となる。これにより得られた粗粒子培地試料の含水量ｂ（ｇ）から、粗粒子培地試料ｂの体積含水率（ｖ／ｖ％）を求めることができる。
【００４５】
上述の測定においては試料はすべて重量で測定されている。なお、混合試料中の粗い培地粒子がその周囲を培地微粒子により囲まれることによって粗い培地粒子の表面での水分ポテンシャルが減少する。しかしながら、粗い培地粒子が多孔質であるため、培地微粒子によって囲まれる表面積が粗い培地粒子が全体として有する表面積に比して僅かなものであるため（１／１００以下）、無視することができる程度のものである。
このようにして求められた粗粒子培地試料の体積含水率は、そのｐＦ値に対応していると考えることができる。そして、このような測定／計算を、種々の圧力において繰り返せば、粗粒子培地の体積含水率とｐＦ値との相関関係（水分保持曲線）を作成することができる。
【００４６】
また、同様に、砂柱法についても、粗粒子試料については水の液絡が遮断されるために正確なｐＦ値の測定ができないが、粗粒子を粉砕して得られる微粒子試料及び粗粒子試料にこの微粒子試料を混合して得られる混合土壌試料については、正確なｐＦ値の測定を行うことができることが分かった。これは、粗粒子の間隙に微粒子が入り込んで水の液絡が形成されるためであると考えられる。したがって、砂柱法によっても、上述のような手順をとることによって、軽石などのような粗い粒子の土壌についても、ｐＨ値と体積含水率との関係、即ち水分保持曲線を求めることができる。
このようにして求められた水分保持曲線と、上述の方法で得られたＡＤＲ計の出力電圧値と体積含水率と較正された相関関係とを用いて、ＡＤＲ計で土壌の測定を行うことにより、その体積含水率を経てｐＦ値を求めることができる。
【００４７】
即ち、本発明によって土壌のｐＦ値の測定する方法は、以下のような構成をとる。
（１）測定対象の粗粒子土壌の粉砕して微粒子試料を成形し、また、粗粒子土壌試料と微粒子試料と混合した混合土壌試料を形成し、同容量の粗粒子土壌試料、微粒子試料及び混合土壌試料を用意して、その重量を計測する。次に、微粒子試料及び混合土壌試料について、加圧板法や砂柱法などの方法によって、ｐＦ値と体積含水率との関係である水分保持曲線を求める。次に得られた結果から、上述した「減算処理」によって粗粒子土壌についての水分保持曲線を求める；
（２）土壌について、ＡＤＲ法などのような電気パルス式土壌誘電率測定法によって、土壌における出力信号値（ＡＤＲ法の場合には出力電圧）を計測して、出力電圧と体積含水率との関係から、土壌の体積含水率を求める。なお、測定対象の土壌に関する出力信号値と体積含水率との関係（較正値）は、予め求めておく；
（３）上記（２）工程で求められた体積含水率から、上記（１）工程で作成された水分保持曲線に基づいて、土壌のｐＦ値を求める；
という手順によって土壌のｐＦ値を測定する。
【００４８】
本発明にしたがって、上記に説明したように土壌の水分量を測定する方法によってｐＦ値を求め、得られたｐＦ値によって灌水を制御することによって、最適条件下で作物の栽培を行うことができる。即ち、上記のように土壌のｐＦ値を一定時間毎に測定し、測定されたｐＦ値と目標とするｐＦ値とを比較して、作物の栽培に最適の条件であるｐＦ１．７〜２．７の域を出ないように灌水又は培養液の供給量を制御することができる。これは、例えば、目標ｐＦを、２．０と設定し、これより高いｐＦ値が測定されたら灌水又は培養液の供給を行い、これより低いｐＦ値が測定されたら灌水又は培養液の供給を停止するという方法によって行うことができる。
【００４９】
本発明は、かかるｐＦ値の測定に基づいて灌水制御を行うための装置を建造物の屋上や地上部分の緑化システムに適用した灌水制御装置を提供する。
即ち、本発明は、培地として粒状軽石を用いた緑化システムの自動灌水制御装置であって、点滴式培養液かけ流し装置と；培養液流路弁を有する点滴装置の送出水量制御手段と；培地の体積含水率を測定する体積含水率測定器と；栽培培地について予め求められたｐＦ値と体積含水率との相関関係が取り込まれており、体積含水率測定器によって測定された培地の体積含水率からｐＦ値への換算を演算処理して、体積含水率測定器の出力結果に基づいて培地のｐＦ値の信号を出力する演算装置と；該演算装置から出力されたｐＦ値信号に基づいて点滴装置への送出水量を抑制する点滴装置制御手段；とを有することを特徴とする自動灌水制御装置を提供する。
【００５０】
更に、本発明の他の好ましい自動灌水制御装置であって、点滴式培養液かけ流し装置と；培養液流路弁を有する点滴装置の送出水量制御手段と；培地の含水率を電気的に検知するセンサとしてのＡＤＲ法、ＴＤＲ法又はＦＤＲ法センサと；栽培培地について予め求められたｐＦ値と体積含水率との相関及び前記センサの検知出力信号と体積含水率との相関関係が取り込まれており、前記センサの検知出力信号から培知の体積含水率への換算及び培地の体積含水率からｐＦ値への換算を演算処理して、前記センサ計の検知出力信号に基づいて培地のｐＦ値の信号を出力する演算装置と；該演算装置から出力されたｐＦ値信号に基づいて点滴装置への送出水量を制御する点滴装置制御手段；とを有することを特徴とする緑化システム用自動灌水制御装置を提供する。
【００５１】
即ち、上記のような灌水制御を行う方法を実施するための装置として、例えば、点滴式培養液かけ流し装置と、培地に挿入されるプローブを有するＡＤＲ計と、該ＡＤＲ計の出力電圧に追従して点滴装置への送出水量を制御する手段とを有するように構成して、固形培地耕式養液栽培装置を構成して、ＡＤＲ計の出力電圧についての追従をタイマーにより一定時間間隔毎に行うようにした固形培地耕式自動灌水制御養液栽培装置を構成することができる。なお、ＡＤＲ計の出力電圧に追従して点滴装置への送出水量を制御することは、好ましくは、対象の栽培培地について予め求められたｐＦ値と体積含水率との相関及びＡＤＲ計出力電圧と体積含水率との相関関係を演算装置に予め取り込んでおき、ＡＤＲ計の出力電圧から培地の体積含水率への換算及び培地の体積含水率からｐＦ値への換算を演算装置によって演算処理して、ＡＤＲ計の出力電圧に基づいて培地のｐＦ値の信号が出力されるように構成し、この出力ｐＦ値信号に基づいて点滴装置への送出量を制御する点滴装置制御手段を設けることによって行うことができる。ｐＦ値の測定値に基づいて培養液流路弁の開閉度を調整する周期については、どの程度の厳密さで制御が求められているかどうかに依存し、これは栽培する作物の種類などによっても異なるが、一般に、１０分〜２時間、好ましくは１０分〜３０分毎に、ｐＦ値の測定に基づいて灌水又は培養液供給の制御を行うことが好ましい。
【００５２】
なお、上記の測定では体積含水率を求める方法としてＡＤＲ法を使用したが、誘電率に基づいて体積含水率を測定できる計器であればＴＤＲ計、ＦＤＲ計などのその他の測定計器を用いることができることは上述した通りである。また、土壌の体積含水率を測定する方法は、誘電率に基づく計測方法でなくとも、土壌の体積含水率を圃場で直接測定することのできる方法であれば、本発明において用いることができる。
本発明装置によってｐＦ値を測定できる培地は、屋上緑化システムを主対象とするために、土壌の流亡防止が最重要視され、必然的に粗大な粒子の軽石が挙げられ、中でも軽石としてはシラス軽石培地について精度よく測定することができる。
なおここで「シラス軽石」については、例えば、上記の「土の環境圏」、３０〜３２頁にその定義と共に説明がなされている。これによれば、「シラス」とは、「後期更新世の大規模なカルデラ火山から噴出した火砕軽石流堆積物の非溶結部またはその２次堆積物」の総称であり、我が国においては、南九州のものがよく知られている。また、これ以外にも、屈斜路湖、十勝岳、支笏湖、洞爺湖、十和田湖、阿蘇山などのカルデラ火山周辺に同様のシラスが分布するが、国土庁の土地分類基本調査等の表層地質図では軽石流堆積物として図示されている。
【００５３】
本発明に係る自動灌水制御装置によって自動灌水制御養液栽培を行うことのできる植物としては、建造物の屋上や地上部分であることを考慮すると、各種園芸用の樹木が適するが、栽培をする作物や草花類でもよい。栽培できる作物の例としては、果菜類、例えば、トマト、ミニトマト、キュウリ、ナス、ピーマン、パプリカ、ジャンボシシトウ、オクラ、インゲン、エンドウ、ニガウリ、ヘチマ、スイカ、メロンなど；葉菜類、例えば、サラダナ、ホウレンソウ、コマツナ、ミョウガ、モロヘイア、エンサイ、チンゲンサイ、リーフレタス、コリアンダー、アロエ、ミツバ、ミニセロリ、パセリ、シュンギク、ラディシュなど；果実類、例えば、パインアップル、パッションフルーツ、パパイア、イチゴなど；花卉類、例えばカーネーション、キク、バラ、サボテン、テッポーユリ、トルコキキョウ、クルクス、ラン、パンジーなど；を挙げることができる。
【００５４】
【実施例】
以下実施例により本発明を具体的に説明する。ただし本発明はこの実施例のみに限定されるものではない。
実施例１（ＡＤＲ法による体積含水率の測定）
粒径が１〜５．６ｍｍの範囲にある鹿児島県産出のシラス軽石培地を用いて、その含水状態を変化させてＡＤＲ法により測定を行ってその出力電圧を計り、出力電圧と軽石培地の体積含水率との関係を調べた。その関係を、横軸がＡＤＲ計の出力電圧、縦軸が体積含水率のグラフにプロットすると、図３に示すグラフが得られた。
【００５５】
実施例２（体積含水率からｐＦ値の算出）
１．試料の調製
粒径が１〜５．６ｍｍの範囲にある鹿児島県産出のシラス軽石試料と、前記軽石を粉砕して粒径が凡そ５０〜２００μｍの範囲にある軽石微粒子試料とをそれぞれ用意した。軽石試料と軽石微粒子試料とを１００ミリリットルずつ秤量した。その重量は軽石試料が５３ｇであり、軽石微粒子試料が７９．４ｇであった。次に、軽石試料と軽石微粒子試料とをほぼ等重量ずつ混合することによって、混合土壌試料を調製した。混合土壌試料１００ミリリットルの重量は７２．５ｇであり、その内訳は、軽石試料が３５．２ｇ、軽石微粒子試料が３７．３ｇであった。
【００５６】
２．混合土壌試料等のｐＦ値及び体積含水率の測定
混合土壌試料について、加圧板法により種々のｐＦ値に対応する体積含水率を測定した。また、軽石微粒子試料についても、同様に加圧板法により種々のｐＦ値に対応する体積含水率を測定した。これらの測定は、各試料の含水状態を変えて幾通りにも測定した。なお、ｐＦ値の測定に加圧板法を使用したのは、加圧板法で測定できるｐＦ値の範囲が実際の好適な栽培条件のｐＦ値範囲に良く入るためである。
３．混合結果によると、第１表に示すように、混合試料Ｍの体積含水率が４４．８（ｖ／ｖ％）のとき、ｐＦ値は１．６であった。また、このｐＦ値において、軽石微粒子試料Ｐの体積含水率は５３．３（ｖ／ｖ％）であった。
この混合試料Ｍの含水量（ｇ）から、混合試料の軽石微粒子分の含水量を減ずることにより、混合試料中の軽石分の含水量を求め、それから軽石試料の体積含水率を算出する。
【００５７】
１００ミリリットルの混合試料Ｍの含水量〔Ａ３〕は、その体積含水率〔Ａ２〕から４４．８ｇであることが分かる。このうち、混合試料１００ミリリットル中の軽石微粒子成分（３７．３ｇ）が保持する含水量〔Ａ４〕は、［５３．３×（３７．３／７９．４）］＝２５．１ｇと計算される。
そうすると、混合試料Ｍ中の軽石成分が保持する含水量〔Ａ５〕は、（〔Ａ３〕−〔Ａ４〕）＝（４４．８−２５．１）＝１９．７ｇとなる。
これは、３５．２ｇの軽石試料が保持する含水量であるから、これを容積１００ミリリットルを軽石全部で満たした場合（軽石重量は５３ｇである）に換算すると、［１９．７×（５３／３５．２）］＝２９．７ｇとなる。
この含水量は、容積１００ミリリットルの軽石試料に含まれるものであるから、その軽石試料の体積含水率は２９．７（ｖ／ｖ％）ということになる。したがって、この軽石試料は、ｐＦ１．６において２９．７（ｖ／ｖ％）の体積含水率を有すると考えることができる。
【００５８】
同様の作業を幾つかのｐＦ値について行い、ｐＦ値と体積灌水率との相関関係を求めた。得られた結果を第１表に示す。第１表には、上記の試料について、ｐＦ１１．６；１．８；２；２．２；２．５及び２．７における結果を示すものであるが、軽石微粒子試料及び土壌試料について、それぞれｐＦ０．４〜２．８の範囲について測定して得られた結果をグラフとして示した図６（ａ）及び（ｂ）であり、この結果から算出された軽石試料の水分保持曲線のグラフを図６（ｃ）として示す。
図６（ｃ）のグラフで示される軽石試料のｐＦ値と体積含水率との関係をみると、本実施例の場合には、ｐＦ値１．６〜２．０の間ではグラフが平らなため十分には使えないが、ｐＦ値２．０〜２．７の間ではｐＦ値と体積含水率との間に一定の相関関係が認められ、これを基にして培地の灌水制御に使用することができる。
実施例２で得られた水分保持曲線を用いて、実施例１で得られたＡＤＲ法による体積含水率の値を換算することによって、その培地のｐＦ値を容易に算出することができる。
【００５９】
【表１】

【００６０】
実施例３（ＡＤＲ法による灌水制御）
粒径が１〜５．６ｍｍの範囲にある鹿児島県産出のシラス軽石培地を用いて、サラダナの栽培を行った。培養液としては園芸試験所標準処方の培養液（「園試処方」と略称されているもので、成分濃度Ｎ：１６ｍｅｑ／リットル（以下同じ）、Ｐ：４、Ｋ：８、Ｃａ：８、Ｍｇ：４）を用いた。まず、セルトレーにそれぞれサラダナの種子を１粒播種して育苗した。育苗２１日後に葉菜用栽培ベッドに、栽培密度４２株／ｍ² で定植した。栽培面積は４ｍ² であった。灌水は、育苗、定植栽培共に、図１に示すような自動制御によって行った。即ち、ＡＤＲセンサ３６で培地の誘電率を測定し、上記実施例１及び２で得られた相関関係をインプットした演算・制御装置３８によって誘電率定値から換算されたｐＦ値に基づき信号３７、３９を送り、灌水の制御を行った。具体的には、設定ｐＦ値を２．０に定め、測定されたｐＦ値がこの値を上回ったら、演算・制御装置３８によって電源盤４８を操作してポンプ３３及び電磁弁３４を作動させ、培養液タンク３２から培養液を点滴チューブ３５に供給して栽培ベッド３１に滴下させて灌水を行い、ｐＦ値が２．０になったら灌水を停止するという自動灌水制御を行った。定植３５日後に収穫とたところ、収穫量は３２０３ｇ／ｍ² であった。また、定植から収穫までの培養液の使用量は８４．６リットル／ｍ² であった。
【００６１】
比較例１（タイマーによる灌水制御）
実施例３と同様の方法で、実施例３の試験と並行してサラダナの栽培を行った。但し、灌水はタイマーにより午前９時及び午後３時の２回行い、それぞれ、栽培ベッドから余剰の培養液が排出されるまで灌水を継続した。収穫は２６９４ｇ／ｍ² 、定植から収穫までの培養液の使用量は１４８．６リットル／ｍ² であった。また、収穫時近くには栽培ベッドの表面に苔様のものが発生していたことがみとめられた。これは、実際の生育に必要な量よりも多い量の培養液が供給されていたことを示すものである。
実施例３と比較例１とを比較すると、本発明に係る灌水制御方法を用いた栽培方法によれば、従来のタイマーによる灌水制御方法と比較して、より少ない培養液量でより高い収穫量を得ることができた。即ち、本発明方法によれば、作物が実際に必要としている量の培養液を正確に制御して供給することが可能になるので、排液等となる余分な供給を防ぐことができる。
【００６２】
実施例４
高さ２０ｍのビルの屋上に縦１００００ｍｍ、横５０００ｍｍ、高さ４００ｍｍ、中の広さが４５ｍ² の四角い枠を設け、その底に防水シートを敷き、この中に粒径が１〜５．６の粒状軽石（シラス）を厚さ２００ｍｍに入れ、直径が約７００ｍｍ、高さ約７００ｍｍのさつきを５０株、縦方向に５列（１０株）になるように植えた。中に入れた粒状軽石の重量は搬入時４０５０ｋｇであった。それに、給水管から培養液を送る点滴掛け流し方式の点滴装置を設置した。ＡＤＲ法で粒状軽石の含水率を測定して、そのｐＦ値を算出して、それに基づいて灌水を行う自動灌水制御装置を設置して前記点滴装置に接続し、前記点滴装置から自動的に灌水を行った。
【００６３】
【発明の効果】
本発明によれば、屋上及び地上緑化用緑化システムにおいて、培地として粒状軽石を用い、かつ粒状軽石のｐＦ値に基づいて、自動灌水制御を行う緑化システム用自動灌水制御装置を使用することにより、建造物に対して重量の負担が小さくてすみ、かつ灌水において水（培養液）の量だけでなく、ｐＦ値という水（培養液）の質までコントロールすることができる。ｐＦ値は連続的電気的に計測できるので、逐次ｐＦ値を読みに行ってきめ細かく灌水することができる。このことにより、肥料及び水の使用量を半減させることができる。しかも、水（培養液）の廃液も出ないシステムになる。このため、屋上の屋根のような培地を支持する支持部の痛みも少なく、建造物の寿命を縮めるようなことがない。
【００６４】
屋上及び地上緑化用培地は、温室の培地と違い、夏暑く、冬は地上より更に低温となり、過酷な環境下におかれるが、各条件に適するように培地の体積含水率を設定して、植物の生育に支障がないようにすることができる。大量に雨が降った場合でも、培地の透水性がよいため、培地に過剰の水が満ち溢れることがなく、屋根に大きな重量が急に掛かることがない。しかもこのような雨が降った場合は、土壌に含まれている肥料成分が流れ出して、環境を汚染することがあるが、この粒状軽石培地はもともとＣＥＣが低いので、流れ出す肥料成分が少ない。このように、ＡＤＲ法等のセンサでのｐＦ値に基づく自動灌水制御装置は、あらゆる環境条件下で、素早く追従して灌水を行うので、極めて優れた効果を奏する。
【図面の簡単な説明】
【図１】本発明の実施例において用いた灌水自動制御栽培装置の概略を示す図である。
【図２】ＡＤＲ法による測定計の概要説明図である。（ａ）は正面図、（ｂ）は平面図である。
【図３】実施例１において行ったＡＤＲ法によるシラス軽石土壌の測定におけるセンサーの出力電圧と体積含水率θとの関係を表すグラフである。
【図４】ｐＦ値と体積含水率との相関関係（水分保持曲線）の測定に使用される加圧板法の概要説明図である。
【図５】水分保持曲線の測定に使用される砂柱法の概要説明図である。
【図６】培地の体積含水率とｐＦ値との関係を表わすグラフであり、（ａ）は粉末試験試料についてのグラフ、（ｂ）は混合試料についてのグラフ、（ｃ）は軽石試料についてのグラフである。
【符号の説明】
１ 土壌水分センサー
２ 本体部
３ センサー部
４ 接続部
５ 信号ロッド
６ シールドロッド
１０ 加圧板装置
１１ 土壌試料
１２ チャンバー
１３ 加圧板
１４ 素焼板
１５ スクリーン
１６ ゴム膜
１７ 加圧装置連通管
１８ 圧力ゲージ
１９ 金属排水孔
２０ 耐圧チューブ
２１ 排水口
２２ ピンチコック
２３ 排水チューブ
２４ 排水ビン
３１ 栽培ベッド
３２ 培養液タンク
３３ ポンプ
３４ 電磁弁
３５ 点滴チューブ
３６ ＡＤＲセンサ
３７、３９ 信号
３８ 演算・制御装置
４０ 電源盤
５１ 砂柱法装置
５２ 水洗いした砂
５３ ポリエチレンシート又は蓋
５４ 採土円筒
５５ 排水口
５６ コック
５７ 余剰水
５８ 水道水
５９ 給水口
６０ コック
６１ 支持台
６２ ブラススクリーン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a irrigation control device with pF value for rooftops of buildings and aboveground greening systems, and in particular, to measure soil moisture in order to facilitate soil management and save water, resources and labor. Further, the present invention relates to a method for determining the pF value of soil by converting this into a pF value, and an irrigation control method for controlling the supply of water or a culture solution to the soil based on the measured pF value, and an apparatus therefor. In addition, the soil here is to support the underground parts such as plant roots and rhizomes, and is composed of coarse particles, for example, coarse particles having a porous surface used in solution cultivation or the like. Means a solid medium such as pumice particles.
[0002]
[Prior art]
Over the past hundred years, the average temperature in Tokyo has risen by 2.9 ° C. In order to stop the “heat island phenomenon” in the city center, the Tokyo Metropolitan Government revised its Nature Conservation Ordinance, and for the first time in Japan decided to require “renewal rooftop greening” for newly renovated buildings. This obliges 20% of the available rooftop space to be planted with trees, turf and flowers.
Conventionally, there are examples of building soil on the roof of a building, which is a building, and planting trees, and in large buildings, making gardens on the roof etc., but planting trees with soil on top of them is very heavy. Because it causes water leakage from the roof, it damages the building, so it is limited to small buildings owned by individuals, and limited to sales-related things when making a garden. For that reason, there was not much special technology for “green rooftop”.
Recently, not only buildings, but also large-scale structures such as artificial ground have been created, and buildings have been built on them. In this case, not only rooftop greening but also soil on the ground part of the building There is a need to form a greening area in a concrete part that has no, but it is at a level where soil is simply put in that part.
[0003]
In the cultivation of crops in the soil, the water content of the soil has a large effect on the growth of the crops.Therefore, drainage is better on land with high water content, and water is irrigated on land with low water content. We devise such as irrigation when there is little time.
For this reason, it is necessary to know the water content in the soil accurately in order to make the crop grow well.
[0004]
Hydroponic cultivation is roughly classified into three types, hydroponics, spray plowing, and solid medium cultivation. Among them, drip pouring is often used in the cultivation method of solid medium cultivation. In this drip pouring method, automatic watering by a timer or the like is generally the mainstream, but optimum watering is not necessarily performed. This is because the amount of culture medium absorbed by the cultivated crop depends on the amount of solar radiation, the temperature and humidity of the greenhouse, and the like. For example, if the amount of solar radiation is large, the temperature of the greenhouse is high, and the humidity is low, the amount of transpiration from the cultivated crop becomes extremely large. On the other hand, the amount of transpiration from cultivated crops decreases on rainy days. Further, the amount of the culture solution absorbed greatly depends on the growth process of the cultivated crop, and when the cultivated crop grows, the amount of the culture solution absorbed becomes very large. It is also known that fruits and the like can be obtained with high sugar content when grown to a certain extent and cultivated with a reduced supply of water. However, automatic irrigation with a timer or the like cannot follow the environmental conditions and the growth process of such cultivated crops, and in order to be able to follow faithfully, the number of irrigation times, the irrigation start time, and the irrigation time must be set. , I have to reset it every day.
[0005]
Even if it is automatic irrigation by a timer or the like, it is useless, and it is doubtful whether optimum irrigation is performed. For these reasons, in automatic irrigation with a timer, etc., the water is often irrigated excessively so that crop wiping does not occur. Problems such as an increase in the amount of liquid and water) could not be avoided.
[0006]
By the way, looking at the relationship between the moisture content in the soil and the cultivation of the crops, not all the water in the soil can be used for the crops, for example, the combined water in the soil cannot be used for the growth of the crops. Considering the change in the moisture content of the soil due to changes in the weather, when heavy rain falls, the soil becomes full of water, but then the water is gradually sucked down and the moisture content of the soil decreases. The state where the soil is full of water is the same state as hydroponics, and the air permeability is poor, so it is not necessarily suitable for outdoor cultivation. Next, when the water content of the soil decreases, the roots cannot absorb water when the water content drops below a certain limit. Will enter. In this state, even if water is subsequently supplied, root wilt is not recovered. Therefore, it is necessary to keep the water content of the soil above this level with this state as the lower limit.
Since the water content of such a soil is determined by the potential of water contained in the soil, it is considered that it is not appropriate to simply represent the water content of the soil related to the cultivation of crops by the water content of the soil. Therefore, a method for expressing the water content based on the water potential of the soil is preferable.
[0007]
By the way, there is a “pF value” as one of the factors representing the moisture state of the soil. The pF value is R.I. K. Proposed in 1935 by Schofield, an index value for the matrix potential of the soil water potential. The matrix potential is a decrease in chemical potential based on the interaction with water soil particles such as capillary force, intermolecular force, and Coulomb force. In short, the matrix potential indicates the strength of the force with which soil particles attract water molecules. The common logarithm of the absolute value of the matrix potential expressed in units of water column (cm) is called “pF value”. The potential φ of the soil water expressed in units of water column (cm) and the pF value have a relationship of pF = log (−10.2φ).
[0008]
The pF value is a quantity representing the quality of water contained in the soil (which is a culture solution in hydroponics). When the pF value is near 0, the soil is filled with water. Water remaining in the soil after 24 hours of rainfall and irrigation (field water volume) is about pF1.7, and from this point to the initial wilting point (pF3.8) at which the crop begins to wilted is called effective water. However, the growth of crops begins to be disturbed when the amount of water is higher than the initial wilting point. This is a state in which the capillary connection of the crop root is cut off and the movement of water from the crop root is stopped. This is called the capillary communication cut point and is about pF2.7. Therefore, in general, when cultivating crops, the pF value is considered to be suitable between pF1.7 and pF2.7. For these reasons, water between pH 1.7 and pF2.7 is called easy water, and it is necessary to maintain this easy water state of pF1.7 to pF2.7 for the cultivation of crops in the soil. It is. In addition, about pF value and the water potential of soil, for example, "Soil environment analysis method", supervised by the Japan Soil Fertilizer Society, edited by Soil Environment Analysis Method Editorial Committee, published by Hirotomo, 1997, 1st printing, 48- 51 pages; "Environment of soil", supervised by Shinno Iwata, published by Fuji Techno System, 1997, pp. 72-76; "Methods and application of soil diagnosis", written by Shunroro Fujiwara et al. Published by Fishing Village Culture Association, 1996, pp. 72-77; “Latest Soil Science”, edited by Kazuyoshi Hisuma, published by Asakura Shoten, 1997, pp. 101-107;
[0009]
In cultivating crops on soil, it is desirable to perform operations such as irrigation based on this pF value.
As a method for measuring the pF value, a tensiometer method is known as a measurement method that can be directly performed on soil in the field.
As a measurement method that can be used effectively in irrigation control in actual cultivation, it is necessary to be able to measure the water capacity of the soil as it is in the field. Therefore, in general farms, the tensiometer method is used to manage optimum irrigation as a method for easily measuring the pF value of soil. In the tensiometer method, a tensiometer composed of an unglazed cup (probe) and a hard transparent vinyl chloride tube is embedded in the soil, the tensiometer is filled with water, and the soil moisture and water in the tube are passed through the unglazed cup (probe) wall. It is made to be continuous, and the soil matrix potential and the pressure in the pipe are in an equilibrium state, and the pressure in the pipe is read as the matrix potential of the soil. Details of the “tensiometer method” are described in, for example, the above-mentioned “soil environment analysis method”, pages 59 to 62.
[0010]
However, since the tensiometer method used in the past requires replenishment of moisture in the apparatus on the spot, the management of the sensor (tensiometer) is difficult, and the pF of soil can be obtained with simpler means or with a simple apparatus. It is desirable to be able to measure values. Also, depending on the quality of the soil, it may not be suitable for using the tensiometer method.
That is, this tensiometer method cannot be used in a solid medium of coarse particles having a porous surface such as soil composed of coarse particles, for example, pumice particles used in hydroponics and the like.
This is because, since the medium is coarse, the medium particles do not adhere to the entire surface of the probe of the tensiometer, and therefore the water of the medium particles does not adhere to the surface of the probe, so that accurate measurement cannot be performed. Therefore, in the past, it was considered that irrigation control using a pF value was desirable even in solid medium cultivation of coarse particles, but it was actually impossible to perform irrigation control using the pF value as an index.
[0011]
At present, there is no alternative to the tensiometer method as a method that can directly measure the pF value in soil.
By the way, as a method for examining the water retention capacity of soil, among the methods that have recently been attracting attention, a method of measuring the soil dielectric constant and determining the volumetric moisture content of the soil from now on has attracted attention. A TDR (Time Domain Reflexometry) method for obtaining the dielectric constant of soil and a FDR (Frequency Domain Reflexometry) method for obtaining the dielectric constant of soil from the characteristics in the frequency domain of electric pulses have been put into practical use. In addition, an ADR (Amplitude Domain Reflectometry) method based on impedance measurement has been proposed as a method for measuring the volumetric water content of soil more easily and inexpensively. For these methods, see “Soil Environmental Analysis”, pages 62-64; Topp, G. et al. C. et. al. (1980): Electromagnetic determination of soil water content: Measurements in coaxial transmission lines. Water Resources Research, 16, 574-582; Horino, Haruhiko & Maruyama, R. (1993): TDR measurement of soil moisture using a 3-wire probe, Proceedings of the Agricultural Civil Society of Japan, 168, 119-120; Kitahira et al. (1996): Measurement of soil moisture by FDR method, Proceedings of Agricultural Civil Engineering Society, pp. 182, 31-38; Makoto Nakajima et al. (1997): Measurement of soil water content using ADR method To page 23; In particular, when using the ADR method, the measurement is very simple, the correlation is high, the measurement apparatus is simple in structure, easy to maintain, easy to handle, and can be continuously measured, so-called maintenance-free. It is. However, these methods determine the volumetric water content of the soil and cannot directly determine the pF value of the soil.
[0012]
[Problems to be solved by the invention]
By the way, in order to prevent the urban heat island phenomenon, in order to plant the trees on the rooftops to green the rooftops of all the buildings to be built, the rooftops of the buildings are waterproofed and the soil is put there as before. Planting trees can be very problematic. Especially in high-rise buildings, a lot of weight-reducing materials are used to reduce the weight on the pillars, but if heavy soil is placed on the roof, it will cause problems in the strength of the building, and it will also be earthquake resistant. Will cause problems.
In addition, not only in buildings but also in large buildings, because the surrounding soil is removed, the surroundings are often made of concrete ground. It is necessary to green the part, but because the bottom is a concrete part, there are problems of waterproofing and weight, etc., and it is not easy to green.
[0013]
In other words, when holding the soil for planting plants on the rooftop or ground part of the building in order to green the rooftop or ground part of the building, there is a problem that the weight of the soil places a burden on the building, and When supplying water or a culture solution to survive a plant planted in the soil, if there is too much water or heavy rain, water leaks to the foundation of the building under the soil. There are problems that cause problems, and that the weight of the soil further increases and the burden on the above-mentioned building becomes more serious. To prevent this, the strength of the building is further increased, or the building is built. There is a need to further strengthen the waterproof structure of the rooftop of things.
In addition, the rooftop of the building is more sunny than the ground, has a large heat capacity throughout the building, and is windy, so that the soil is in a condition suitable for plant growth, and the soil does not fly. It was difficult to set supply conditions.
[0014]
The present invention eliminates the above-mentioned problems in order to green the rooftop and ground part of a building, and when the culture medium for planting plants on the rooftop and ground part of the building is held, the culture medium is the building. The weight that puts a burden on the medium is low, and the amount of water and culture solution supplied to survive the plants planted on the culture medium that is held is low, causing the problem of water leakage to the foundation of the building under the culture medium. In addition, there is almost no need to increase the strength of the building so that the weight of the culture medium is further increased by supplying water or the like and the burden on the building is not increased. An object of the present invention is to provide an irrigation control device for a greening system so that the waterproof structure of the roof portion of the roof is not complicated.
[0015]
In addition, the present invention provides means for enabling the irrigation control device of the greening system to measure the pF value of the medium using a method for examining the water retention capacity of the soil without using the conventional tensiometer method. It is intended to do.
Another object of the present invention is to provide a method and apparatus for measuring the pF value of a medium immediately and continuously using a method for examining the water retention capacity of soil and controlling irrigation using the measured value. It is what.
[0016]
Furthermore, the present invention provides means that can measure the pF value of the soil even when the pF value of the soil cannot be directly measured by the tensiometer method or the like, in particular, means that can measure the soil continuously. It is an object of the present invention to provide a method and apparatus for controlling irrigation.
The present invention further provides a water retention measurement method that is simple and easy to measure in the case of soil that cannot use a tensiometer, especially porous large-diameter particles such as pumice, in hydroponics in solid medium cultivation. An object of the present invention is to provide a method and an apparatus for measuring the amount of water in soil that enables irrigation control using a pF value. Furthermore, an object of the present invention is to provide an irrigation control device for a greening system such as a rooftop using a technique that enables irrigation control based on a pF value in cultivation in solid medium cultivation.
[0017]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above-mentioned object, the present inventor adopted a light granular pumice medium as a medium in order to reduce the weight to the building as much as possible, and comparatively by the above ADR method or the like. Focusing on the fact that there is a correlation depending on the type of soil, that is, soil properties, between the volumetric water content of the soil and the pF value that can be easily measured, the volumetric water content and the pF for the medium to be measured in advance. After determining the correlation with the value, by measuring the volumetric water content of the medium, the pF value is determined from this, and by controlling irrigation with this value, there is no effect on plant growth, and the granular pumice medium It has been found that the amount of water that is held and supplied to it can be very small, thereby minimizing the weight of water on the building, and the present invention has been completed. In the following, the term “culture solution” includes the case of only water.
[0018]
  That is, this invention solved the said subject by the following means.
(1) On the roof of the building and on the groundUsing granular pumiceHold the medium,An infusion apparatus for supplying culture medium to the culture medium, a measurement apparatus for measuring the volumetric water content of the culture medium, an arithmetic device for calculating the pF value of granular pumice based on the output of the measurement apparatus, A control unit for controlling the amount of liquid delivered to the drip device based on the pF value of the granular pumice from the arithmetic unit;In planting planting system,The correlation between the pF value and the volumetric water content of the cultivation medium incorporated in the arithmetic device is
(A) A coarse soil sample to be measured is pulverized to prepare a fine particle sample;
(B) preparing a mixed soil sample by mixing a coarse soil sample with a fine particle sample at a predetermined weight ratio;
(C) For the mixed soil sample and the fine particle sample, obtain the correlation between the volumetric water content and the pF value;
(D) obtaining a correlation between the volume moisture content and the pF value for the coarse soil sample based on the correlation value between the volume moisture content and the pF value obtained for the mixed soil sample and the fine particle sample;
Is obtained in advanceAn automatic irrigation control device for a greening system.
(2) The measuring apparatus for measuring the volumetric water content of the granular pumice medium has an ADR method, a TDR method, or an FDR method as a sensor that electrically continuously detects the moisture content of the granular pumice medium. To(1)The automatic irrigation control apparatus for greening systems as described.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
In this invention, although granular pumice is used as a culture medium for greening, the range of the particle size is preferably 1 to 5.6 mm.
Further, the granular pumice preferably has a saturated water permeability coefficient of 0.3 to 0.8 cm / sec, an air permeability coefficient of 15 to 40 cm / sec for dry and wet samples, and an ion exchange capacity of 3.0. The thing of -4.0 meq / 100g is preferable.
When using granular pumice as the culture medium, the water retention of the culture medium is good, so when stacked on the roof, there is no problem with the growth of trees even if it is thin compared to normal soil. For example, in the case of a pine tree with a tree height of 3 m In the latter case, it is sufficient if the thickness is 40 cm, and for satsuki and azaleas, the thickness is 20 cm.²A weight of 90 kg per hit is enough to hang on the rooftop.
Furthermore, granular pumice has good water permeability, so even if it rains, most of the water is drained, and in the case of granular pumice with a thickness of 20 cm, the granular pumice layer after 1 hour weighs 1 m.²It is enough to increase about 10kg per hit.
[0020]
Next, means for obtaining the pF value of granular pumice from the measurement result of the volumetric water content of the granular pumice medium used in the irrigation control device of the present invention and controlling the amount of water delivered by the drip device based on the pF value will be described in detail.
The method according to the present invention is based on the concept of measuring the volumetric moisture content of the soil and determining the volumetric moisture content in the pF value of the soil.
The water retention capacity of soil can be expressed by various factors, such as volume water content and pF value. As a method of measuring the volumetric moisture content, there can be mentioned a gravimetric method in which a soil sample is collected and its moisture weight is measured. However, in order to directly measure the volumetric moisture content of the soil in the field, a sample is taken. This method cannot be used because continuous measurement is not possible.
As a means for directly measuring the volumetric water content of the soil at the field site, there is a method that has recently attracted particular attention as a method for obtaining the volumetric water content of the soil by measuring the dielectric constant of the soil by an electric pulse method. Since this method measures a certain area of the soil, there is little fluctuation in the measured value, and the measurement work is simple and excellent. In addition, measurement can be performed very quickly, continuous measurement is easy, and the correlation between the electrical output signal and the volumetric water content is high. However, what can be measured by this electric pulse method is the volumetric water content of the soil, and no means has been developed for determining the pF value, which is an indicator of the amount of water available to plants.
[0021]
The TDR method is a representative method of the electric pulse method, and its measurement principle is that the relative permittivity of water is 81, the relative permittivity of soil solid substance is about 4, and the relative permittivity of air is 1 The volume moisture content of soil is measured by utilizing the fact that an empirical correlation is established between the apparent relative dielectric constant and the amount of water. A specific measuring means inserts two or three parallel electrodes into the soil, applies a microwave thereto, and measures the propagation time of the interference reflected wave. When the length of the electrode is L and the propagation time of the reflected wave is t, the propagation speed V of the microwave is given by V = 2L / t. Theoretically, the relative dielectric constant Ka is inversely proportional to the square of the microwave propagation velocity V, so Ka = (C / V)²The relative dielectric constant can be obtained by Here, C is the speed of light in vacuum.
As a similar method, there is an FDR method for obtaining the dielectric constant of soil from the characteristics of interference reflected waves in the frequency domain. These methods can measure the volumetric water content of soil and can be used in the method of the present invention.
However, these methods have a drawback of requiring an expensive oscilloscope or the like for measuring the propagation speed of the pulse.
[0022]
Recently, the ADR method has been developed as a method which has performance comparable to these methods and can be measured more easily. This ADR method is a method for measuring the volumetric water content of soil simply and inexpensively by simple impedance measurement. Therefore, it is a more preferred method for use in the present invention.
The ADR method uses the principle that the relative permittivity Ka of the soil is greatly influenced by the volumetric water content (θ), and thus obtains θ from the Ka-θ relationship. The ADR method is the same as the method, but the ADR method measures the impedance (Z) of the transmission line when a high-frequency electric pulse travels back and forth through the probe in the soil as a means for measuring the relative permittivity Ka to determine Ka. It is different in point to ask.
FIG. 2 is a schematic diagram of the soil moisture sensor 1 based on the ADR method. (A) is the front view, (b) is a top view. This sensor probe incorporates a 100 MHz sinusoidal oscillator, a coaxial transmission line area and a measurement electronic circuit in the main body 2, and the sensor 3 is composed of four parallel stainless steel rods. As shown in FIG. 6B, the sensor rod 3 has a signal rod 5 at the center and a shield rod 6 that forms an electrical barrier around the signal rod. This sensor part behaves as an additional area of the transmission line and has a Z that depends approximately on the dielectric constant of the soil in the range of 26.5 mm in diameter surrounded by the shield rod 6.
[0023]
The signal of the oscillator propagates along the transmission line through the sensor probe, and when the Z of the sensor unit 3 is different from Z in the coaxial transmission line of the main body, a signal of a certain magnitude is transmitted between the signal rod and the transmission line. It is reflected from the connection part 4 and returns. The ratio of the signal that is reflected and returned is called the reflection coefficient ρ.
The reflection coefficient is interfered with the incident signal that is the cause of the voltage standing wave generated by the interference between the incident wave and the reflected wave, that is, the amplitude of the voltage along the length of the transmission line.
And the initial peak voltage v of the transmission line₀And the peak voltage v at the connection_jIs designed to have a certain relationship, the difference in amplitude is expressed by a relational expression that is a function of the impedance of the transmission line and the impedance of the probe in the soil matrix.
[0024]
By measuring this difference in amplitude, the relative impedance of the sensor section is evaluated and the following equation:
[0025]
[Formula 1]

[0026]
Thus, the dielectric constant Ka is obtained. Where r₁And r₂Is the radius of the signal and blocking electrodes and F is the form factor. From the calculated relative permittivity Ka of the soil, the following formula:
θ = -5.3 × 10^-2+2.92 × 10^-2Ka-5.5 × 10^-FourKa²+4.3 × 10^-6Ka^Three
From the empirical formula, the volumetric water content θ (m^Three・ M^-3).
Note that the amplitude of the voltage standing wave has a characteristic of decreasing as the soil moisture increases (relative permittivity increases). In this case, the moisture content of the soil is separately measured by the gravimetric method, etc., measured by the ADR method, etc., to obtain the output signal value (for example, output voltage), and measured by changing the moisture content of the soil. Can be used to obtain a calibrated relationship line between the volumetric water content from the soil water content and the output voltage, and a means for obtaining an accurate volumetric water content of the soil by on-site ADR measurement. .
Thus, the volumetric water content of the soil can be determined by a method based on a dielectric constant such as the ADR method. FIG. 2 shows the relationship between the output voltage of the sensor and the volumetric water content θ in the ADR method. It can be seen that there is a correlation between them.
[0027]
As described above, according to the dielectric constant-based method, particularly the ADR method, the volumetric water content of the soil can be easily and easily obtained. In addition, in the ADR method, the average dielectric constant of the soil on the upper part of a cylinder having a certain diameter is obtained. Therefore, the sensor probe does not have to be in close contact with the soil particles, and there is an advantage that the volumetric water content can be measured even in soils with coarse particles such as pumice particles. In the above and the following description, a method of outputting a voltage by an ADR meter and obtaining a volume moisture content based on the voltage is described. However, in the method of the present invention, based on other output signal values by the ADR meter. The volumetric moisture content may be obtained, or the volumetric moisture content may be obtained based on the output signal value of another type of sensor such as a TDR meter or an FDR meter.
[0028]
However, the volumetric water content of the soil obtained by such measurements, that is, the water content, includes the amount of water that cannot be used for plants, such as soil bound water, so it corresponds well with the amount of water that can be used for plants. The pF value is different.
In the present invention, the pF value of the soil is obtained by converting the measurement result of the volumetric water content of the soil thus obtained by the ADR method or the like into the pF value of the soil.
[0029]
The matrix potential (pF value) of the soil sample and the volume moisture content have a specific correlation depending on the soil properties, and this is called a moisture retention curve. As a method for measuring a moisture retention curve of a soil sample, that is, a correlation between a matrix potential and a volume moisture content, a sand column method, a suction method, a pressure plate method, a pressure membrane method, and the like are known. Among these methods, except for the sand column method, the volumetric water content corresponding to the matrix potential is determined by measuring the weight of the soil when reaching the equilibrium state by applying a predetermined pressure to the soil sample. Is obtained at various pressures to obtain moisture retention curves for the soil sample. The sand column method performs the same measurement by giving a predetermined position potential to the soil sample placed on the sand column instead of applying pressure to the soil sample.
[0030]
In the present invention, paying attention to the fact that there is a correlation depending on soil properties between the volumetric moisture content of the soil and the pF value in this way, a moisture retention curve (correlation line) is previously set for the soil to be measured. The pF value of the soil is obtained from the value of the volumetric water content of the soil obtained by a method such as the ADR method as described above using a correlation line. When the correlation line is a table, it may be based on a conversion table, or an approximate expression if possible. As a means for obtaining the pF value of the soil from the value of the volumetric moisture content of the soil using the correlation line, for example, the output signal of the ADR meter is input to an arithmetic device incorporating the correlation line obtained in advance to correspond to the pF value of the soil. It is preferable to use means using an arithmetic unit such as a microcomputer incorporating a program for outputting a signal.
[0031]
In the following, regarding the soil, the correlation between the volume moisture content and the pF value is examined to create a relationship line, the volume moisture content of the soil is determined based on the dielectric constant, and the volume determined based on the created relationship line The method according to the present invention for determining the pF value of soil from the moisture content will be described.
First, it becomes basic data for creating a relationship line (moisture retention curve) between the volumetric water content and the pF value. PF values corresponding to various volumetric water contents of the soil are determined by methods known in the art. Since the pF value needs to be accurate, a measurement method performed indoors is adopted. Examples of the pF value measurement method performed in a known room include a sand column method, a pressure plate method, a suction method, a pressure film method, and a vapor pressure method. Among these, it is said that the sand column method is suitable for measurement in the range of pF value of 0.5 to 1.4, and the pressure plate method is suitable for measurement of pF value in the range of 1.6 to 2.7. Further, although a method called “centrifugation” has been proposed as a method for measuring the pF value, this method has not yet been put into practical use. Therefore, it can be said that the pressure plate method is most suitable as a method that meets the object of the present invention to keep the water content of the soil within the range of easy water of pF = 1.7 to 2.7. However, other methods such as a sand column method can also be used in the present invention.
[0032]
For example, when the pF value of soil is measured by the pressure plate method, it is performed as follows.
First, the technical contents of the pressure plate method will be briefly described with reference to FIG. The pressure plate apparatus 10 includes a pressure chamber 12 and a pressure plate 13, and the pressure plate 13 has a structure in which a screen 15 is sandwiched under the unglazed plate 14 and covered with a rubber film 16. A pressure gauge 18 is provided in the pressurizing chamber 12, and the air pressure in the chamber is read.
When the soil sample 11 is placed on the clay-sintered plate 14 saturated with water and air pressure is applied from the pressurizer communication pipe 17, the soil water held at a potential higher than the matrix potential balanced with the air pressure passes through the clay-sintered plate 14. Drained. The soil water passes from the metal drain hole 19 through the pressure-resistant tube 20 and the drain port 21, and enters the drain bin 24 through the drain tube 23 having the pinch cock 22. An exhaust valve 25 is provided for decompressing the pressurizing chamber 12. By changing the air pressure stepwise, the water retention amount corresponding to each matrix potential can be measured. The sample soil is taken out and weighed together with the pressure plate for each air pressure. The water content is determined by calculating the difference between the measured weight of the soil sample and the weight of the dry soil sample. Since the water content obtained here corresponds to the air pressure at that time, that is, the water potential at that time, the water content corresponding to a certain pF value is obtained. Moreover, based on the bulk specific gravity of soil, a volumetric water content will also be calculated | required.
By repeating this operation by changing the air pressure stepwise, a comparison table of various pF values and corresponding volumetric water contents is created. When the values in the table are plotted on a graph with the pF value on the horizontal axis and the volumetric water content on the vertical axis, a moisture retention curve is obtained.
[0033]
Similarly, the principle of the sand column method, which is a method for measuring the pF value of soil, will be described with reference to FIG.
FIG. 5 is a diagram showing an outline of the sand column method apparatus 51. Usually, fine sand that has passed through a sieve of 250 μm or less or quartz sand whose particle size is adjusted to 300 to 180 μm is used. The column is filled with sand 52 washed with water in advance, the cock 60 is opened, and tap water 58 is introduced from the water supply port 59 to saturate the sand with water. A support base 61 and a brass screen 62 are disposed at the bottom of the column so as to hold a sand column. Then, the particle arrangement is stabilized by applying vibrations by hitting the periphery. In order to prevent evaporation from the top surface of the sand column, a polyethylene sheet or a lid 53 is put on. It is more effective to put a lid on the colored clay cylinder 54 as well. A soil sample (colored clay cylinder) 54 is placed on the sand column 52, and the height of the movable drainage port 55 is fixed to the upper end of the sand column to saturate the soil sample 54 with water. Next, the movable drain port 55 is lowered to a predetermined position, and the cock 56 is opened to drain the excess water 57, thereby lowering the water level of the free water surface in the sand column, thereby dehydrating the soil sample. . The water level L is read by the water level gauge 63. When dehydration is completed, the mass of the soil sample at that time is measured to determine the volumetric water content. The matrix potential (cm) of the soil sample at this point is represented by-(L + 1/2), where the thickness of the soil sample is 1. Thereby, the volume moisture content of the soil sample in a predetermined pF value is calculated | required.
[0034]
By repeating this operation by changing the water level L stepwise, a comparison table between various pF values and the corresponding volumetric water content is created. When the values in the table are plotted on a graph with the pF value on the horizontal axis and the volumetric water content on the vertical axis, a moisture retention curve is obtained.
[0035]
On the other hand, with respect to the same soil, the output signal value, for example, the output voltage, is measured with, for example, an ADR meter for the sample whose volume moisture content is known, and a calibrated conversion table between the output voltage and the volume moisture content of the soil is created. When this result is plotted on a graph with the output voltage on the horizontal axis and the volumetric water content on the vertical axis, a relational line as shown in FIG. 3 is obtained.
[0036]
Thus, if a relation line is created in advance and the moisture content of the soil is measured using, for example, an ADR meter at the field of a general farm, as a first step, an output voltage created in advance from the output voltage of the ADR meter. The volumetric moisture content of the soil is determined based on the relationship line between the volumetric moisture content and the volumetric moisture content. Next, as a second step, the moisture retention curve (volumetric moisture content and The pF value of the soil can be determined based on the relationship line with the pF value.
If the two relational lines described above are put into the arithmetic unit, the pF value of the soil can be calculated from the output voltage signal of the ADR meter using an electronic circuit, and the numerical value can be displayed on the display. Becomes extremely simple.
Alternatively, the pF value signal of the soil obtained by the calculation can be sent to the control circuit of the irrigation apparatus, and the water supply apparatus of the irrigation apparatus can be operated.
[0037]
According to the method of the present invention, it is possible to directly and continuously measure the pF value of soil much more easily than the conventionally used tensiometer method, and irrigation control can be performed using this measurement result. It can be carried out. Further, in the tensiometer method, the pF value could not be measured for a medium composed of coarse particles having a porous surface such as pumice, but according to the method of the present invention, a porous material such as the ADR method can be used. The pF value can be determined by measuring the volumetric water content by a method applicable to a quality medium.
[0038]
In the present invention, depending on the pressure plate method or the sand column method used as a method for measuring the correlation (moisture retention curve) between the pF value and the volumetric water content, a special soil or medium, particularly a porous surface is used. The soil (medium) consisting of particles cannot be measured. For example, when pumice with a particle size of 1 to 5.6 mm is used as a medium, the pressure plate method measures the accurate pF value because the contained water is not continuous even when pressure is applied between the particles. Because you can't. That is, since the contained water does not exist continuously in the pumice particle culture medium or the like, the capillary water of capillary action is not connected, so that a correct pF value cannot be measured. Further, in the sand column method, in the case of a pumice medium, there is no water junction, so an accurate pF value cannot be measured. Therefore, when the method of the present invention is used to measure the pF value for soil composed of particles having a porous surface, further ingenuity is required. Hereinafter, this point will be described in detail.
[0039]
When the present inventors examined whether the pF value of a pumice medium could not be measured by the pressure plate method or the sand column method, the pF value could not be accurately measured with a sample containing only coarse medium particles. It was found that the pF value can be measured for a mixture of coarse medium particles and fine medium particles. Then, a soil sample of coarse medium particles and a medium fine particle sample prepared by pulverizing the medium sample are prepared, and further, a mixed soil sample in which the coarse medium particle soil sample and the medium fine particle sample are mixed and dispersed. PF value of the medium fine particle sample and the mixed soil sample is measured, and the obtained result is subjected to a “subtraction process” described below to obtain the pF value of the soil sample of coarse medium particles. I found that I can do it. In the following, this method will be described in detail.
[0040]
First, a coarse medium, for example, a medium composed of pumice coarse particles having a particle diameter of 1 to 5.6 mm is prepared. Next, medium fine particles are prepared by pulverizing the coarse particle medium. Moreover, the mixed soil sample which mixed and disperse | distributed said pumice coarse particle and culture medium fine particle is prepared. In this case, the pumice coarse particles and the medium fine particles are preferably mixed in equal weights, but are not necessarily equal in weight. However, in that case, the mixing weight ratio is confirmed.
[0041]
With respect to the medium fine particle sample and the mixed soil sample thus obtained, the relationship between the pF value and the volumetric water content, that is, the moisture retention curve is obtained by a method such as a pressure plate method. This method will be described below. In the following description, for convenience, a pumice coarse particle medium sample is sample B, a medium fine particle sample prepared from pumice coarse particles is sample A, and a mixed soil sample obtained by mixing sample A and sample B is sample C. An example is pF value measurement by a pressure plate method.
[0042]
Sample A composed of medium fine powder can measure the pF value by the pressure plate method, but pumice coarse particle sample B cannot measure the pF value by the pressure method. However, the pF value can be measured for the mixed soil sample C. This is presumably because blow-through does not occur when fine particles enter the gaps between the coarse particles. Therefore, it is desirable that the particle size of the medium fine particle sample used for preparing the mixed soil sample is such that the fine particles enter the gaps between the coarse particles. Furthermore, the size needs to be such that the fine particles do not enter the pores of the porous coarse particles. This is because if the fine particles enter the pores of the porous coarse particles, the behavior changes, and an accurate pF value cannot be measured. In general, the particle size of the fine particle sample is preferably about 50 to 200 μm, but is not limited to this value.
[0043]
As described above, the pF value cannot be measured for the coarse particle sample B, but the pF value can be measured for the fine particle sample A and the mixed soil sample C. Therefore, the measurement result for the sample B is obtained from the measurement result for the mixed soil sample C and the measurement result for the fine particle sample A by “subtraction processing” described below.
For the mixed soil sample C and the fine particle sample A, the relationship between the pF value and the volumetric water content, that is, the moisture retention curve is measured by the pressure plate method. These measurements are made in various ways by changing the water content of each sample.
[0044]
Let x be the volumetric water content of mixed soil sample C at a certain pF value._c(V / v%), where the water content of a predetermined volume of the mixed soil sample is c (g), the amount of water retained by the fine particles in the mixed soil sample [c_a(G)] is a value obtained by multiplying the moisture content [a (g)] that the medium fine particle sample A of the same volume has in its pF value by the weight ratio of the medium fine particles in the mixed soil sample. That is, the weight of the medium fine particles in the predetermined volume of the mixed soil sample is z_ca(G) The weight of the medium microparticle sample of the same volume is z_a(G) c_a= A x (z_ca/ Z_a) Next, from the water content [c (g)] of the mixed soil sample C, the amount of water [c_aIf (g)] is reduced, the amount of water retained by the coarse particles in the mixed soil sample C [c_b(G)] is required. C_b= C-c_aIt becomes. Then, when the amount of water is divided by the ratio of the coarse medium in the mixed sample, the water content of the coarse particle medium sample B can be calculated. That is, the weight of coarse particle culture medium sample B of the same volume is z_b(G) When the water content of the coarse particle medium sample B is b (g), b = c × (z_b/ Z_cb) The volumetric water content (v / v%) of the coarse particle culture medium sample b can be obtained from the water content b (g) of the coarse particle culture medium sample thus obtained.
[0045]
In the above measurement, all samples are measured by weight. It should be noted that the moisture potential on the surface of the coarse medium particles is reduced by surrounding the coarse medium particles in the mixed sample with medium fine particles. However, since the coarse medium particles are porous, the surface area surrounded by the medium fine particles is very small compared to the surface area of the coarse medium particles as a whole (1/100 or less), and can be ignored. belongs to.
It can be considered that the volumetric water content of the coarse particle culture medium sample thus obtained corresponds to the pF value. If such measurement / calculation is repeated at various pressures, a correlation (moisture retention curve) between the volumetric water content of the coarse particle culture medium and the pF value can be created.
[0046]
Similarly, in the sand column method, since the liquid junction of water is blocked for the coarse particle sample, an accurate pF value cannot be measured. However, a fine particle sample and a coarse particle sample obtained by pulverizing the coarse particles It was found that an accurate pF value can be measured for a mixed soil sample obtained by mixing the fine particle sample. This is presumably because fine particles enter the gaps between the coarse particles to form a liquid junction. Therefore, the relationship between the pH value and the volumetric water content, that is, the moisture retention curve can be obtained for the coarse particle soil such as pumice by the sand column method as well.
By measuring the soil with the ADR meter, using the moisture retention curve thus obtained, the output voltage value of the ADR meter obtained by the above method, the volume moisture content, and the calibrated correlation, The pF value can be obtained through the volumetric water content.
[0047]
That is, the method for measuring the pF value of soil according to the present invention has the following configuration.
(1) A coarse particle soil to be measured is pulverized to form a fine particle sample, and a mixed soil sample is formed by mixing the coarse particle soil sample and the fine particle sample. Prepare a soil sample and measure its weight. Next, with respect to the fine particle sample and the mixed soil sample, a moisture retention curve which is a relationship between the pF value and the volumetric water content is obtained by a method such as a pressure plate method or a sand column method. Next, from the results obtained, the moisture retention curve for the coarse-grained soil is determined by the “subtraction process” described above;
(2) For the soil, the output signal value (output voltage in the case of the ADR method) in the soil is measured by an electric pulse type soil permittivity measurement method such as the ADR method, and the output voltage and the volumetric water content are calculated. From the relationship, determine the volumetric water content of the soil. In addition, the relationship (calibration value) between the output signal value and the volumetric water content related to the soil to be measured is obtained in advance;
(3) From the volumetric water content obtained in the step (2), the pF value of the soil is obtained based on the moisture retention curve created in the step (1);
The pF value of the soil is measured by the following procedure.
[0048]
According to the present invention, as described above, the pF value is obtained by the method of measuring the moisture content of the soil, and the cultivating of the crop can be performed under the optimum condition by controlling the irrigation by the obtained pF value. . That is, the pF value of the soil is measured at regular intervals as described above, and the measured pF value is compared with the target pF value, and pF 1.7-2. The supply amount of irrigation or culture solution can be controlled so as not to leave the range of 7. For example, the target pF is set to 2.0, and if a higher pF value is measured, the irrigation or culture solution is supplied. If the lower pF value is measured, the irrigation or the culture solution is supplied. This can be done by stopping.
[0049]
This invention provides the irrigation control apparatus which applied the apparatus for performing irrigation control based on the measurement of this pF value to the greening system of the rooftop of a building, or the ground part.
That is, the present invention is an automatic irrigation control device for a greening system using granular pumice as a culture medium, a drip-type culture fluid pouring device; a delivery water amount control means of a drip device having a culture fluid flow path valve; A volumetric water content measuring device for measuring the volumetric water content of the medium; a correlation between the pF value and the volumetric water content determined in advance for the cultivation medium is incorporated, and the volumetric water content of the medium measured by the volumetric water content measuring device A computing device that computes the conversion from the rate to the pF value and outputs a signal of the pF value of the culture medium based on the output result of the volume moisture content measuring device; based on the pF value signal output from the computing device An automatic irrigation control device comprising: an infusion device control means for suppressing the amount of water delivered to the infusion device.
[0050]
Furthermore, another preferred automatic irrigation control device of the present invention, which is a drip-type culture solution pouring device; a delivery water amount control means of the drip device having a culture solution flow path valve; and electrically detecting the water content of the medium ADR method, TDR method or FDR method sensor as a sensor to perform; correlation between pF value and volume moisture content determined in advance for the culture medium and correlation between detection output signal of the sensor and volume moisture content are incorporated Then, the conversion from the detection output signal of the sensor to the volumetric water content of the culture and the conversion from the volumetric water content of the culture medium to the pF value are processed, and the pF value of the culture medium is calculated based on the detection output signal of the sensor meter. And an infusion device control means for controlling the amount of water delivered to the infusion device based on the pF value signal output from the computation device; To provide a device.
[0051]
That is, as an apparatus for carrying out the method for performing irrigation control as described above, for example, a drip-type culture solution pouring device, an ADR meter having a probe inserted into a medium, and the output voltage of the ADR meter are tracked. And a means for controlling the amount of water delivered to the drip device, to form a solid culture medium culture solution culture device, and to follow the output voltage of the ADR meter at regular time intervals by a timer The solid culture medium type automatic irrigation control nutrient solution cultivating apparatus can be configured. It should be noted that controlling the amount of water delivered to the infusion device following the output voltage of the ADR meter is preferably a correlation between the pF value obtained in advance for the target culture medium and the volumetric water content, and the ADR meter output voltage. The correlation with the volumetric water content is taken into the calculation device in advance, and the calculation device converts the conversion from the output voltage of the ADR meter to the volumetric water content of the culture medium and the conversion from the volumetric water content of the culture medium to the pF value. The apparatus is configured to output a pF value signal of the culture medium based on the output voltage of the ADR meter, and by providing an infusion device control means for controlling the delivery amount to the infusion device based on the output pF value signal. be able to. The period for adjusting the degree of opening and closing of the culture fluid flow path valve based on the measured value of the pF value depends on the degree of strict control required, and this depends on the type of crop to be cultivated. In general, it is preferable to control irrigation or culture solution supply based on the measurement of the pF value every 10 minutes to 2 hours, preferably every 10 minutes to 30 minutes.
[0052]
In the above measurement, the ADR method was used as a method for obtaining the volumetric water content. However, other measuring instruments such as a TDR meter and an FDR meter can be used as long as the meter can measure the volumetric water content based on the dielectric constant. What can be done is as described above. Further, the method for measuring the volumetric water content of the soil can be used in the present invention as long as it is a method capable of directly measuring the volumetric water content of the soil in the field, without being a measurement method based on the dielectric constant.
Since the culture medium that can measure the pF value by the apparatus of the present invention is mainly used for rooftop greening systems, prevention of soil runoff is regarded as the most important, and pumice with coarse particles is inevitably mentioned. Pumice medium can be measured accurately.
Here, “Shirasu Pumice” is described together with its definition in, for example, “Soil Environmental Zone” on pages 30 to 32 above. According to this, “Shirasu” is a general term for “the unwelded part of pyroclastic pumice flow deposits or its secondary deposits erupted from a large caldera volcano in the late Pleistocene”. The ones in South Kyushu are well known. In addition, similar shirasu are distributed around caldera volcanoes such as Lake Kussharo, Mt. Tokachi, Lake Shikotsu, Lake Toya, Lake Towada, and Mt. Aso. Is shown as pumice flow deposits.
[0053]
As a plant capable of performing automatic irrigation control hydroponic cultivation with the automatic irrigation control device according to the present invention, considering various types of horticultural trees, it is suitable for cultivation, considering that it is a rooftop or a ground part of a building. It may be a crop or a flower. Examples of crops that can be cultivated include fruit and vegetables such as tomatoes, cherry tomatoes, cucumbers, eggplants, peppers, paprika, jumbo citrus, okra, green beans, peas, bitter gourd, loofah, watermelon, melon, etc .; leaf vegetables such as salad na Spinach, Komatsuna, Myouga, Morohea, Ensai, Chingensai, Leaf lettuce, coriander, aloe, honey bee, mini celery, parsley, garlic, radish, etc .; fruits, such as pineapple, passion fruit, papaya, strawberry; Carnation, chrysanthemum, roses, cactus, teppo lily, turkeys, crux, orchids, pansies, etc.
[0054]
【Example】
The present invention will be specifically described below with reference to examples. However, the present invention is not limited to this example.
Example 1 (Measurement of volumetric water content by ADR method)
Using a Shirasu pumice medium produced in Kagoshima Prefecture with a particle size in the range of 1 to 5.6 mm, changing its water content and measuring by the ADR method, measuring its output voltage, the output voltage and the volume of the pumice medium The relationship with water content was investigated. When the relationship is plotted on a graph in which the horizontal axis is the output voltage of the ADR meter and the vertical axis is the volumetric water content, the graph shown in FIG. 3 is obtained.
[0055]
Example 2 (calculation of pF value from volumetric water content)
1. Sample preparation
A shirasu pumice sample produced in Kagoshima Prefecture with a particle size in the range of 1 to 5.6 mm and a pumice fine particle sample with a particle size in the range of about 50 to 200 μm were prepared by pulverizing the pumice. The pumice sample and the pumice fine particle sample were weighed 100 ml each. The weight was 53 g for the pumice sample and 79.4 g for the pumice fine particle sample. Next, a mixed soil sample was prepared by mixing the pumice sample and the pumice fine particle sample at substantially equal weights. The weight of the mixed soil sample 100 ml was 72.5 g, and the breakdown was 35.2 g for the pumice sample and 37.3 g for the pumice fine particle sample.
[0056]
2. Measurement of pF value and volumetric water content of mixed soil samples
About the mixed soil sample, the volumetric water content corresponding to various pF values was measured by the pressure plate method. Moreover, the volumetric water content corresponding to various pF values was similarly measured about the pumice fine particle sample by the pressure plate method. These measurements were made in various ways by changing the water content of each sample. The reason why the pressure plate method was used for the measurement of the pF value is that the range of pF values that can be measured by the pressure plate method is well within the pF value range of actual suitable cultivation conditions.
3. According to the mixing result, as shown in Table 1, when the volume water content of the mixed sample M was 44.8 (v / v%), the pF value was 1.6. Moreover, in this pF value, the volumetric water content of the pumice fine particle sample P was 53.3 (v / v%).
From the water content (g) of the mixed sample M, the water content of the pumice fine particles in the mixed sample is reduced to obtain the water content of the pumice in the mixed sample, and then the volumetric water content of the pumice sample is calculated.
[0057]
It can be seen that the water content [A3] of the mixed sample M of 100 ml is 44.8 g from its volume water content [A2]. Of these, the water content [A4] retained by the pumice fine particle component (37.3 g) in 100 ml of the mixed sample is calculated as [53.3 × (37.3 / 79.4)] = 25.1 g. .
Then, the water content [A5] retained by the pumice component in the mixed sample M is ([A3]-[A4]) = (44.8-25.1) = 19.7 g.
Since this is the water content retained by the 35.2 g pumice sample, when converted to a case where the volume of 100 ml is filled with all pumice (the pumice weight is 53 g), [19.7 × (53 / 35.2)] = 29.7 g.
Since this water content is contained in the pumice sample having a volume of 100 ml, the volume water content of the pumice sample is 29.7 (v / v%). Therefore, this pumice sample can be considered to have a volumetric water content of 29.7 (v / v%) at pF 1.6.
[0058]
The same operation was performed for several pF values, and the correlation between the pF value and the volume irrigation rate was determined. The results obtained are shown in Table 1. Table 1 shows the results at pF 11.6; 1.8; 2; 2.2; 2.5 and 2.7 for the above samples, and for the pumice particulate sample and the soil sample, respectively. FIGS. 6A and 6B are graphs showing the results obtained by measuring in the range of pF 0.4 to 2.8. The graph of the moisture retention curve of the pumice sample calculated from the results is shown in FIG. Shown as 6 (c).
Looking at the relationship between the pF value and the volumetric water content of the pumice sample shown in the graph of FIG. 6 (c), in the present example, the graph is flat between the pF values of 1.6 to 2.0. Therefore, a certain correlation is observed between the pF value and the volumetric water content between the pF values of 2.0 and 2.7, and the medium is used for irrigation control of the medium based on this correlation. be able to.
By using the moisture retention curve obtained in Example 2 and converting the volumetric water content value obtained by the ADR method obtained in Example 1, the pF value of the medium can be easily calculated.
[0059]
[Table 1]

[0060]
Example 3 (irrigation control by ADR method)
Saladana was cultivated using a Shirasu pumice medium produced in Kagoshima Prefecture having a particle size in the range of 1 to 5.6 mm. As a culture solution, a culture solution of a garden garden laboratory standard formulation (which is abbreviated as “garden trial formulation”, component concentration N: 16 meq / liter (hereinafter the same), P: 4, K: 8, Ca: 8, Mg: 4) was used. First, one seed of Sorana seed was sown on each cell tray and nurtured. Cultivation density 42 strains / m on leafy vegetable cultivation bed 21 days after raising seedlings²Planted in The cultivation area is 4m²Met. Irrigation was performed by automatic control as shown in FIG. That is, the dielectric constant of the culture medium is measured by the ADR sensor 36, and the signals 37, 39 are based on the pF value converted from the constant dielectric constant by the arithmetic / control device 38 to which the correlation obtained in the first and second embodiments is input. To control irrigation. Specifically, the set pF value is set to 2.0, and when the measured pF value exceeds this value, the operation panel 38 is operated by the operation / control device 38 to operate the pump 33 and the solenoid valve 34, The culture solution was supplied from the culture solution tank 32 to the drip tube 35 and dropped onto the cultivation bed 31 to perform irrigation. When the pF value reached 2.0, the irrigation was stopped. When harvested 35 days after planting, the yield was 3203 g / m.²Met. The amount of culture solution used from planting to harvesting is 84.6 liters / m.²Met.
[0061]
Comparative example 1 (watering control by timer)
In the same manner as in Example 3, Salana was cultivated in parallel with the test in Example 3. However, irrigation was performed twice at 9 am and 3 pm with a timer, and irrigation was continued until the excess culture solution was discharged from the cultivation bed, respectively. Harvest is 2694 g / m²The amount of medium used from planting to harvesting is 148.6 liters / m²Met. In addition, it was found that moss-like material was generated on the surface of the cultivation bed near the time of harvest. This indicates that a larger amount of culture solution than that required for actual growth was supplied.
When Example 3 and Comparative Example 1 are compared, according to the cultivation method using the irrigation control method according to the present invention, compared with the conventional irrigation control method using a timer, a higher yield is obtained with a smaller amount of culture solution. Could get. That is, according to the method of the present invention, it is possible to accurately control and supply the amount of culture solution actually required by the crop, and therefore, it is possible to prevent an excessive supply of drainage or the like.
[0062]
Example 4
On the roof of a building with a height of 20m, it is 10000mm long, 5000mm wide, 400mm high, and 45m wide.²A rectangular sheet is provided, a waterproof sheet is laid on the bottom, and granular pumice (shirasu) with a particle size of 1 to 5.6 is placed in a thickness of 200 mm, and the surface is about 700 mm in diameter and about 700 mm in height. 50 plants were planted in 5 rows (10 strains) in the vertical direction. The weight of the granular pumice put in was 4050 kg at the time of carrying in. In addition, a drip-flow drip apparatus for sending the culture solution from the water supply pipe was installed. An ADR method is used to measure the moisture content of granular pumice, calculate its pF value, and install an automatic irrigation control device that performs irrigation based on the pF value, connect to the infusion device, and automatically irrigate from the infusion device Went.
[0063]
【The invention's effect】
  According to the present invention, in the greening system for rooftop and above-ground greening, by using granular pumice as a medium and using an automatic irrigation control device for a greening system that performs automatic irrigation control based on the pF value of granular pumice, The weight of the building can be reduced, and not only the amount of water (culture solution) but also the quality of water (culture solution) as pF value can be controlled in irrigation. Since the pF value can be measured continuously and electrically, go to read the pF value sequentiallyTextureCan be finely irrigated. As a result, the amount of fertilizer and water used can be halved. In addition, the system does not generate waste water (culture medium). For this reason, there is little pain of the support part which supports culture media like a roof of a roof, and it does not shorten the lifetime of a building.
[0064]
  The medium for rooftop and aboveground greening, unlike the medium in the greenhouse, is hot in the summer, and is colder than the ground in the winter, and is placed in a harsh environment, but the volumetric water content of the medium is set to suit each condition, The plant can be prevented from growing.In large amountsEven when it rains, the medium has good water permeability, so that the medium is not filled with excess water, and a heavy weight is not suddenly applied to the roof. Moreover, when such rain falls, fertilizer components contained in the soil may flow out and pollute the environment. However, since this granular pumice medium originally has a low CEC, there are few fertilizer components flowing out. As described above, the automatic irrigation control device based on the pF value of a sensor such as the ADR method performs irrigation quickly following all environmental conditions, and thus has an extremely excellent effect.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of an automatic irrigation cultivation apparatus used in an example of the present invention.
FIG. 2 is a schematic explanatory diagram of a measuring instrument based on the ADR method. (A) is a front view, (b) is a plan view.
3 is a graph showing the relationship between the sensor output voltage and the volumetric water content θ in the measurement of Shirasu pumice soil by the ADR method performed in Example 1. FIG.
FIG. 4 is a schematic explanatory diagram of a pressure plate method used for measurement of correlation (moisture retention curve) between pF value and volumetric moisture content.
FIG. 5 is a schematic explanatory diagram of a sand column method used for measurement of moisture retention curves.
FIG. 6 is a graph showing the relationship between the volumetric water content of the medium and the pF value, where (a) is a graph for a powder test sample, (b) is a graph for a mixed sample, and (c) is a graph for a pumice sample. It is a graph.
[Explanation of symbols]
1 Soil moisture sensor
2 Body
3 Sensor part
4 connections
5 Signal rod
6 Shield rod
10 Pressure plate device
11 Soil samples
12 chambers
13 Pressure plate
14 Unglazed plate
15 screens
16 Rubber film
17 Pressurizer communication pipe
18 Pressure gauge
19 Metal drainage hole
20 Pressure-resistant tube
21 Drainage port
22 pinch cock
23 Drain tube
24 Drainage bottle
31 cultivation bed
32 Medium tank
33 Pump
34 Solenoid valve
35 drip tube
36 ADR sensor
37, 39 signals
38 Computing and control devices
40 Power panel
51 Sand column method equipment
52 Sand washed with water
53 Polyethylene sheet or lid
54 Mining cylinder
55 Drain outlet
56 cock
57 Surplus water
58 tap water
59 Water inlet
60 cock
61 Support stand
62 Brass screen

Claims (2)

A drip-flow type drip device that holds a medium using granular pumice on the roof and the ground of a building and supplies a culture solution to the medium, a measuring device that measures the volumetric water content of the medium, and the measuring device A planting device for calculating a pF value of granular pumice based on the output, and a means for controlling the amount of liquid delivered to the infusion device based on the pF value of the granular pumice from the computing device, and planting a plant in the medium In the system, the correlation between the pF value and the volumetric water content of the cultivation medium incorporated in the arithmetic device is
(A) A coarse soil sample to be measured is pulverized to prepare a fine particle sample;
(B) preparing a mixed soil sample by mixing a coarse soil sample with a fine particle sample at a predetermined weight ratio;
(C) For the mixed soil sample and the fine particle sample, obtain the correlation between the volumetric water content and the pF value;
(D) obtaining a correlation between the volume moisture content and the pF value for the coarse soil sample based on the correlation value between the volume moisture content and the pF value obtained for the mixed soil sample and the fine particle sample;
An automatic irrigation control device for a greening system, characterized in that it is obtained in advance .   The measuring apparatus for measuring the volumetric water content of the granular pumice medium has an ADR method, a TDR method, or an FDR method as a sensor for electrically continuously detecting the moisture content of the granular pumice medium. Item 2. An automatic irrigation control device for a greening system according to item 1.

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