For the second year in a row, Cultivators organized, with the support of GreenTech Americas in Mexico to help lead the conversation around hydroponic leafy greens in Latin America. Together with partners and speakers from across the value…
Published on 08/03/2022
Gartenbau Van den Broek (Paul, Marcel & Jolanda van den Broek) have been growing tomatoes in Germany for over 10 years now. Since 2021, they have started cultivating aubergine (eggplant) on 1.25 ha. Of course, with many years of experience in tomatoes, they have a strong foundation to realise high production in aubergines. However, they requested support with the basics of aubergine growing. And as Cultivators, we are partners in growing businesses and experienced in aubergines.
Van den Broek received positive news from an eggplant grower nearby about Tom Moerenhout of Cultivators. In an initial discussion between Tom and Paul, it became clear that success in aubergine cultivation depends on fine details. A difference of half a degree Celsius can significantly impact critical moments during the growing period. As a result, Paul decided to work closely with Tom, who has over 20 years of experience in aubergine cultivation. Together, they managed to achieve an exceptional first year of growing.
The growers built the greenhouse a few years ago using diffuse glass (20% haze) with a double AR coating. This is an uncommon feature in aubergine cultivation in Western Europe. They also installed a double screen system and equipped the aubergine compartment with Hinova Ventilation Jets. Both are welcoming tools for eggplant cultivation, as it is a crop that thrives in tropical conditions.
For example, in tomatoes, they have only one screen installed, but tomatoes require a lower pre-night temperature. In an aubergine, you need more energy to keep a pre-night temperature of 17-18 degrees Celsius. During the night, you will increase the temperature to reach 20-21 degrees by morning. The 24-hour temperatures are higher as well as working with a higher RH, which is different to their tomato crops.
Climate is not the only difference between a tomato and an aubergine. One of the key challenges is harvesting the fruits. According to Tom’s experience, most people require nearly a year to complete this task correctly at a sufficient pace. You need to ‘read’ the fruits on aspects as type of fruit, age and quality to identify the proper harvesting moment. Tomatoes are much easier, as you pick them when they turn red. Also, harvesting eggplants at height (on trolleys) is different from harvesting tomatoes, as you lower the crop so you can harvest on the ground.
Another aspect is the density of the crop itself, with large leaves and numerous side branches that carry fruits. This last aspect brings us to one of our key learning and goals for the coming season. Learning how to optimally top/pinch side branches, as we noticed last year, is that keeping 3 or 4 flowers is excessive. To maintain sufficient growth speed in plants and fruits, we need to manage pinching more closely. A max of 2 per side branch to improve crop balance and easier harvesting. Overall, Paul was surprised by the number of fruits that can be obtained from just one aubergine plant over one crop season. The harvesting scheme and strategy are also different from those of other vegetable crops. The demand in Germany is for smaller fruits; therefore, there is a need to harvest three times per week all year round.
Van den Broek is growing Tracey of Rijk Zwaan as the main variety with Maxifort (de Ruiter) as rootstock. Holland Plant propagated the pinched plants in the Netherlands and planted them on 10 cm high GT Master NG2.0 slabs from Grodan on xx December 2021.
A system with four stems per plant and a density of approximately five stems/m2. In aubergine, it is important to maintain uniformity at the top of the plant by topping heads. For new eggplant growers and the labour force, it is something they need to learn. Tom trained the team and explained that crop registration plays a crucial role in maintaining balance in the crop, aligning it with the predicted light levels.
Not expected by Paul were the challenges with pests & diseases compared to tomatoes. Aubergine is more vulnerable to pests like thrips, spider mites, and aphids, as well as new bugs and beetles. Another point of attention, according to Paul, was the time required to change the crop, since the amount of plant residue is much higher, requiring more labour. Additionally, for the staff, it was not the best period to work in the greenhouse under such dusty conditions.
Paul concludes we still have a lot to learn about growing aubergines. Using the extra light that deepens into the canopy due to scattering is crucial. And of course, the first season, you ‘play safe’ as we were worried the crop could not handle the summer, therefore we were sometimes too vegetative. The start of the current season has already been better than last year, as we have managed to develop a strong, balanced crop so far. Together with Tom as a consultant, we will work on further improvements in generative steering and gain more experience in what we achieve with diffuse glass in this crop.
Both Paul and Tom were pleasantly surprised by the crop’s performance under diffuse glass last season. With a much better start this season, both hope to reach this year the goal of 65 kg/m². With a greater focus on pieces (rather than kilos), this would be a serious achievement. Of course, a drier summer with good light levels would help to reach this goal. Anyway, ending the first aubergine growing season with about 62-63 kg/m² is a performance that van den Broek and Tom are proud of.
