日射比例給液制御によってビート栽培したイチゴ’女峰’の生育，収量と養水分吸収

Nutrient and water uptake, growth and yield of strawberry (Fagaria × ananassa Duch. cv. Nyoho) grown in peat-based substrate with contralled fertigation corresponding to solar radiation (SR) were composed with that of time-scheduled fertigation (TS). Amount of nutrient solution for each treatment was changed seasonally to keep the amount of drainage as 30-50ml/plant/day. The amount of each fertigation (y, ml/plant; 4 times a day) was automatically controlled with the following equation in SR; y= (24x + 17.5) c, where x: comulative solar radiation after the previous fertigation (kW ・hr/m2) and c:0.7-2.0 (factor changed seasonally according to the aomunt of drainage), while the amount was set as 24.6 -77.6ml/plant (4 times a day) in TS. There was little difference between the two fertigation systems in growth, yield and the amount of absorbed nutrients. However, nutrients and water were absorbed more efficiently and nutrients were discharged with drainage less in SR than in TS. Relationship between water consumption and solar radiation varied seasonally, in which the slope of the regression was larger in April and May compared to before March. EC value of the drainage increased to 1.5 times or more of applied solution when the amount of drainage was small, but the EC and concentration of nutrients in the drainage varied little when discharge rate (amount of drainage / supplied solution) was larger than 15% or drainage was more than 30ml/plant/day. When strawberries are grown with substrate, optimum value of the discharge rate may be 15 to 20%. To maintain this value, the factors of a controlling device for solar-mediated fertigation should be changed in a timely manner depending on the seasonal changes in evapotranspiration rate affected by leaf area of plants and/or environmental conditions in a greenhouse.

ピートモスを主体とする培地で養液栽培したイチゴ‘女峰’の生育，収量と養水分吸収について，液量30～50ml/株/日を目標として毎回の給液量を一定の値（24.6～77.6ml/株）に設定し，点滴給液した固定区を対照とし，給液量（ｙ：ml/株）を前回の給液からの積算日射量（ｘ：kW・hr/㎡）に基づいて変動させて点滴給液する［ｙ＝(24ｘ＋17.5)ｃ，ｃ：0.7～2.0］日射比例制御区（比例区）との比較を行った．生育，収量については処理区間にほとんど差が認められず，養分の総吸収量にも大きな差は認められなかった．しかし，対照区と比較して比例区では，養水分の利用効率が高く，排液とともに排出される養分が少なかったことから，日射比例給液制御によって環境に対する負荷を小さくできることが明らかになった．イチゴの蒸発散速度と日射量との間の関係は季節によって異なり，葉面積が大きくなる４月以降は回帰式の傾きが大きくなった．また，排液が少ない場合には排液のECが施与した培養液の1.5倍以上と著しく高くなったが，排液率（給液量/液量）が15%，あるいは排液量が30ml/株/日以上の場合には，排液のECと排液中養分濃度が安定した値を示した．これらのことから，イチゴを固形培地で養液栽培する場合には，葉面積やハウス内環境条件の季節的な変動による蒸発散速度の変化に合わせて，排液率が15～20%となるように日射比例給液制御の設定値を変更することが望ましいと考えられた．