The German cultivation company Gartenbau Drechsler grew a standard crop this year. They could because they still had a fixed energy contract. Next season, they may start the new, non-lit crop later. Grower Christoph Schmidt thinks insights provided by the model-based crop planning platform, ProJoules, can also help growers cultivate more efficiently.
This year, he used the platform for the first time in Abenberg. That coincides with his first year as a grower at the German company, which also has a cultivation site in Nuremberg. "I worked there part-time until last year," begins Christoph, "until I graduated. I studied information technology. That means a lot of computer work. In my new job, which I started last fall, I can nicely combine growing and computer work."
Drechsler built a five-hectare greenhouse on the Abenberg site in 2018. It consists of six sections in which they grow different types of tomatoes. At their other location, the growers cultivate cucumbers and eggplants too. "Abenberg had more space to build a new, modern greenhouse," Christoph says, explaining why his employer, Christian Drechsler, chose that spot. "He and I arrange cultivation and labor here together. I'm always onsite, while Christian is also at the location."
Dutch cultivation consultant Willem van Dijk told these German growers to take a look at the ProJoules platform. "We'd already used Excel sheets. Those were fine, but the ProJoules platform effortlessly shows you everything at a glance. The dashboard gives you a nice overview. Also, I no longer have to draw graphs; that helps tremendously."
Varying greenhouse climates
The growers cultivate various kinds of tomatoes on perlite: TOVs, cocktail, plum, and three colors of snack tomatoes for a color mix. "Four climate zones are set up for growing the larger tomatoes. Two are set up for growing snack tomatoes. The greenhouse climate's biggest difference is how much the day and night temperatures we use to grow snack tomatoes differ," Christoph continues.
Summer 2022 was quite extreme, with lots of sunshine, high temperatures, and very little rain. "Our rainwater reservoirs ran dry, and we had to get some of our water from other sources. That happened in 2018 too."
ProJoules has given the growers good insight into the amount of irradiation in joules. ProJoules' model focuses on how much light there is in the greenhouse at the plant level. "In the summer, the plants stress because there's so much light. By entering last year's data into ProJoules, we were far more aware of when that would happen. We then applied coating," says Schmidt.
The growers never used to coat the greenhouse. "We didn't know exactly when to apply it either." ProJoules has given the growers that insight. They coated the greenhouse between weeks 26 and 33. "Afterward, it was evident we were getting better production in the summer weeks than before." By the end of week 36, their volumes were three kilograms above 2021 production.
The growers also regularly suffered blossom end rot because of plant stress. "When there's a lot of sun in the summer, and thus a calcium deficiency, this is an often-recurring problem in the plum tomatoes." This year, there was almost no blossom end rot. "That's a big difference from other years," admits Christoph.
They are expecting the current crop to last until about week 40. Christoph hopes to exceed last year's production by four or five kilograms. Using the model, the grower has insight into what he can still harvest. "In snack tomatoes, too, we're heading for a record. There we have two kilograms more than our previous record."
The growers are anxious to see when they can plant the next season's crop. That's usually about two weeks before Christmas, but the energy crisis is making growers cautious. They have not yet decided on an exact start date. What is certain is that energy-efficient cultivation will enjoy the extra attention. "We can definitely use the ProJoules insights for that," says Christoph.
He is well pleased with the overviews the platform has already provided, as well as the communication. "It's a new platform, so improvements are still being made, making communication vital. The ProJoules team is always easy to reach. If I suggest ideas, they are open to them. That's nice."
Next season, Christoph plans to enter even more climate and water data to have a complete overview of the entire crop in the portal. He has always entered that data himself, in the current platform too. But that is not an issue for him. "Each variety takes me five to ten minutes a week. However, I find the time I put in is well worth it when I see what it means for our production and the insights I'm now getting," he concludes.