Nutritional management of gerbera (Gerbera jamesonii) grown in a closed soilless culture system

Gerbera plants were planted in 4 litre pots filled with pumice and supplied via a fully automated installation with nutrient solution prepared by replenishing the drain solution with nutrients and water. The addition of nutrients and water to the drain solution was based on real time measurements of its volume and electrical conductivity. This data was utilized by a computer controlled system to automatically calculate and add to the drain solution as many nutrients and water as needed to achieve a target electrical conductivity in the supply solution. In each watering application, the entire volume of drain solution collected after the previous watering application was reused. Replenishment of the drain solution with nutrients was based on addition of concentrated fertilizer solutions. The nutrient ratios in the concentrates were so arranged that, after diluting them at a particular ratio with tap water without addition of drain solution, a reference nutrient solution having a composition recommended as optimal for the supply solution could be obtained. However, since the drain solution was recycled. the actual nutrient concentrations in the supply solution could not be identical to those of the reference nutrient solution. After about 9 months of nutrient solution recycling according to the above method, nutrient solution samples were collected from all watering applications of one day and from both the supply solution and the drainage. The results indicated that the K/Ca, Mg/Ca and P/(SO42- +NO3-) ratios in the reference nutrient solution should be higher than the values suggested for the supply solution.