WUR: Electric substrate heating bears more strawberry fruit

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 4^oC above the temperature of the unheated control, respectively. The average realized substrate temperature was ultimately approximately 1.5 and 3^oC 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 +4^oC 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 4^oC 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 4^oC treatment, had a significant positive effect on the number of harvested fruit. This means that significantly more flowers were induced by the 4^oC 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.

Source: Wageningen University & Research