In a strawberry experiment, more fruit were harvested when using substrate heating than without heating. The test in Bleiswijk was carried out by Wageningen University & Research, BU Glastuinbouw with an everbearer strawberry variety from ABZ Seeds in a January planting with assimilation lighting. The electric heating experiment was commissioned by Warmgras B.V., who also supplied the heating equipment.
Three different treatments were included in the experiment: a control without heating and two heated treatments with electrical heating of the substrates. The target temperature of the two heated treatments was 2 and 4oC above the temperature of the unheated control, respectively. The average realized substrate temperature was ultimately approximately 1.5 and 3oC higher than in the control, respectively. Because the electrical heating did not always work optimally, causing a difference in theoretical and actual electricity consumption of almost 50%. Over the entire period, the energy consumption of the +4oC treatment was 19.3 kWh/m2.
Over the entire harvest period, there was a tendency that root heating positively affected the number of fruits. Compared with the unheated control, the number of fruits increased by 5% and 15% in the 2 and 4oC treatment, respectively. At the highest substrate temperature, this seemed to decrease the fruit weight.
From the end of April to mid-June, substrate heating, especially in the 4oC treatment, had a significant positive effect on the number of harvested fruit. This means that significantly more flowers were induced by the 4oC treatment. There was also a tendency that total harvested weight increased in this period. Substrate heating did not negatively affect the internal and external fruit quality.