Effects of coco fibre addition to perlite on growth and yield of cut Gerbera

The experiment was carried out in Naples during a 12-month period, in a heated glasshouse (set point 12 °C). The effects of the addition of an upper coco fibre layer to perlite on growth and productivity of cut gerbera grown in pot in an open hydroponic system were investigated. Plants of Gerbera jamesonii cultivar Leader were cultivated at the planting density of 5.5 plants per m2 and fertilized via a drip-system. EC and pH of nutrient solution were kept at 1.6 dS m-1 and 6.0 respectively and the number of pulses ranged from 1 (October-January) to 7 (July) per day (400 ml per pulse). The addition of the upper layer of coco fibre to the perlite raised the leaf water potentials (-0.74 vs -0.84 MPa) and the rates of net assimilation (13.7 vs 12.1 mol CO2 m-2 s-1) and transpiration (6.01 vs 5.19 mmol H2O m-2 s-1) of Gerbera plants compared to the perlite only, and higher differences were observed during the warmer months. The substrate significantly influenced the plant growth: plants on perlite +coco fibre had larger leaf area per plant compared to P, due to both the higher leaf number and the larger unitary leaf area, and produced more cut stems (53 vs 44.4 stems per plant), with no significant difference in stem quality between the two substrates. The cumulated water consumption was higher in plants grown with the addition of coco fibre compared to those grown on perlite (71.6 vs 58.9 L plant-1). Chemical analysis revealed a significant higher content of P and K in leaf tissues of plants grown with the addition of the organic medium.