An important development in the field of strawberry cultivation is the shift from uncovered to covered cultivation. This development has been going on for years, but it seems to be pushed more and more. It is expected that the number of greenhouse strawberries will double in ten years’ time. In the meantime, growers aim to get their product to market earlier every time, which is the cause of the big energy challenge, says Bart Jongenelen of Delphy in a blog on Dutch greenhouse energy resource ‘Kas als Energiebron’.
“The sector is facing a big challenge in terms of distribution and pricing. It is normal to use the so-called ‘continuous cultivation,’ causing the production to arrive all at once. With a fresh planting (plant date at the end of December – beginning of January) the goal is to get to the market sooner than when using continuous cultivation. To realize this goal, crops are forced by using high temperatures during the winter months. Energy-wise, this will become a fun challenge in the future.”
“We chose to use a cultivation strategy in which we start with a fresh planting with the Sonsation variety, followed by an ever-bearing crop in the period of June-November/December for the 2019 project. The production periods of this strategy are different in comparison to the traditional continuous cultivation, so there is no need to use supplementary lighting.”
Equipment of the greenhouse
The choice was made to use two energy screens so that it is possible to have maximum isolation in the winter period (Luxous 1147 from below and Luxous 1547D from above). The heating surface has also been expanded, and they are working with a maximum temperature of 45 ⁰C for both the bottom net and the crop heating pipes. These are all essential adjustments to ensure a longer peak consumption, but most important is the adjustments made to the cultivation strategy.
It is normal to operate with a big difference between day and night in strawberry cultivation. After relatively high temperatures during the day, temperatures decline rapidly to around 8 or 10 ⁰C. At the beginning of the trial, a small difference between day and night was used, and the cooling and heating occurred more slowly. As the crops grew, the day and night difference increased as well. The base heating temperatures are lower compared to the reality, but this is compensated by the high amount of light influences during both the day and night. This way the amount of light at any given hour on a bright day is higher than on a cloudy day.
Starting production later
So far, this strategy seems to be working with regards to energy usage. The combined gas usage in the 13th week reached 4 m3 per m2, with a peak consumption of 0.6 m3 per m2 per week at most. This is only half of what is typically used. The only downside is the belated production start. The harvest in the NGG department started over a week later than in the normal greenhouse. The temperature use in both greenhouses is reasonably similar. The delay is caused by the lower amount of lighting in the NGG greenhouse. Due to the intensive use of screens during the day, light also gets screened out. The right balance needs to be found here as well.
The above-mentioned project 'Greenhouse Strawberry Future Proof' is financed by the ‘Kas als Energiebron’ program, the innovation and action program of Greenhouse Horticulture Netherlands and the Ministry of Agriculture, Nature and Food Quality. A diversity of other parties also contribute to this project in terms of funding or in another way, among which are Flevoberry, Ludvig Svensson, Nivola, and BVB Substrates.
Source: Kas als Energiebron