Nutrient and Water Uptake, Growth and Yield of Substrate Cultured Strawberry cv. Nyoho with Solar-Mediated Fertigation Control

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.