“Fine-tuning your irrigation strategy based on data produces impressive results”
As a highly innovative company, BASF Vegetable Seeds is keen to explore how automation can benefit all areas of its operations. Since 2019, the company has been applying data-driven growing and the Plant Empowerment principles in a tomato greenhouse at one of its facilities in the Dutch town of ’s-Gravenzande. The aim is to balance the key inputs in order to optimize plant health and maximize production. Frans Goud, a crop technician at BASF, explains how his partnership with stonewool specialist Saint-Gobain Cultilene to fine-tune the irrigation strategy has produced eye-opening results.
At BASF Vegetable Seeds they are very open to the idea of autonomous growing and the use of data to optimize results, according to Frans Goud. “People are subjective and tend to make decisions based on their gut instinct. But even experienced growers can misinterpret a situation. Data enables you to make objective decisions and reduces the chance of mistakes. Besides that, automatic controls help to stabilize the production and give you greater peace of mind, while automation reduces the amount of manual work and frees up more time for a grower to spend on other things,” he says. “If we can use automation to make the production process as predictable as possible, as an extra service to our clients we can supply all our seed varieties with precise instructions for how to get the best out of that particular variety. We already do that for lettuces, and we’re now keen to do the same for tomatoes.” Therefore, in 2019, BASF started a two-year greenhouse trial to grow its main tomato variety, Provine, on 500m2 in line with the Plant Empowerment principles.
To overcome a couple of technical issues in the first year, the team decided to install a new hybrid lighting system of 65% LEDs and 35% HPS from Hortilux for the second year – and the switch to hybrid lighting called for a different approach to the irrigation strategy. “We were very happy with the substrate products we were using from stonewool specialist Saint-Gobain Cultilene: OptimaXX slabs and RootmaXX cubes. To collect all the data, we installed ten sensors, which is quite a lot for just 500m2, but this gives us very good averages of all the values,” explains Goud. “And besides supplying the substrate, Saint-Gobain Cultilene also provided a lot of support and advice on how we could get the best out of the substrates by looking at the climate as a whole, especially in view of the new lighting system. The most eye-opening advice was to how to treat the substrates at the beginning of the season to get the plants off to a more generative start. After all, to maximize the kilos, you need to produce fruits, not leaves!”
Remy Maat, Application Manager at Saint-Gobain Cultilene, helped Goud to focus on achieving the right amount of dryback in the slab at the beginning. “He suggested to go for 30% dryback in the slab in the first couple of weeks of the season to encourage the roots to search for the available water, whereas I would have been inclined to stop at 20%. So I tried it, and he was right; this approach resulted in a very even spread of the roots throughout the entire substrate,” recalls Goud. “What I particularly like about the Saint-Gobain Cultilene products is that they don’t seem to have layers, like substrates from some other suppliers do, so the entire volume of stonewool is optimally utilized from top to bottom, all season long. As a result, the pH and EC remain very stable.”
Once the second season was underway, Maat also advised Goud on the ideal frequency and duration of waterings in combination with the lighting strategy. “In the second year, we used the lights at 300µmol HPS for 18 hours a day. Rather than starting at around midnight, we started a couple of hours later to minimize the number of hours that the bumblebees would be exposed to artificial light only. Around two hours after turning the lights on, we initiated dryback until we reached 9-10%. Then we started watering generously and frequently in order to achieve drain after around three hours,” he explains. “But another thing I learned from Saint-Gobain Cultilene was to interrupt the watering an hour before sunrise until an hour after sunrise. At the start of the day, something happens in the natural light spectrum that activates the root pressure, so there’s a higher risk of giving too much water. This can make the plant too vegetative, causing the fruits to split and reducing the flower quality.”
The hybrid lighting system and data-driven approach also meant that BASF worked with a different irrigation strategy at the end of the day. “Without artificial lighting, we would normally stop watering two or three hours before sunset. Now, we could use the data to see how much water the plant needed, when to stop, and if any extra waterings were needed in order to achieve at least 10-15% dryback overnight. This is important in order to keep sufficient oxygen in the substrate,” continues Goud.
Strong and healthy roots
All the sensors enabled Goud to monitor the plants’ need for water and also to anticipate the likelihood of water stress. “It gets harder for the plant to transport water to the head towards the end of the season and the roots struggle to keep up when evaporation is high. Late last summer, for example, our plants were around 16m tall with an average of 46 trusses per plant! The data gave us good insight into the conditions and helped us to continue to provide sufficient water on time to minimize water stress,” he comments. “Besides the productive nature of the plants, another sign of their strong and healthy roots is that we had hardly any issues with mildew or whitefly throughout the season.”
New trial with cherry tomatoes
BASF’s aim in the second year of the Provine trial was to achieve a minimum of 100kg/m2. “That would be a realistic production level based on the manual technique, so we wanted to at least match this by following the Plant Empowerment principles,” says Goud. “During the cycle, we realized that we were well on track to achieve that, and by the end of August 2021 we discovered that we’d produced 121kg/m2 – so over 20% more than expected.” Based on the success of this project and the lessons learned, BASF is now fine-tuning its approach in a similar trial with cherry tomatoes, which started in October 2021. “In the case of cherry tomatoes, what matters most is the taste – that’s what people are prepared to pay for,” he states. “The flavour is dictated by the Brix value and this requires a higher EC, but working with a very high EC can reduce your annual production level by as much as 6kg/m2. So we’re keen to see how focusing on the data will enable us to push the production level to the max while achieving the desired flavour.”
Besides receiving irrigation-related support from Saint-Gobain Cultilene and working with Hortilux on the lighting system, Goud also has regular contact with other Plant Empowerment Implementation partners – namely Hoogendoorn Growth Management for greenhouse climate control, Koppert Biological Systems for nutrition, pollination and pest management, the LetsGrow data platform and Ludvig Svensson for the screening strategy. He describes it as an optimal partnership: “We exchange opinions, make suggestions, discuss ideas and challenge each other’s standpoints based on an atmosphere of trust and respect for each other’s specific area of expertise. Ultimately, we all share the same goal – pushing the boundaries without losing sight of what’s best for the plant. And we all agree that it’s OK to make mistakes, as long as we learn something useful from them.”
For the full 100%
“Above all, what I learned from last season is that steering your irrigation strategy in line with the temperature and evaporation data enables you to avoid giving too much water unnecessarily. Besides improving production, this also has numerous efficiency benefits in terms of reducing your water consumption, energy consumption and waste of fertilizers, for example,” says Goud. “People are often sceptical about new ideas and may be afraid of taking risks in a commercial operation. I regularly hear that growers are doing 90% of what is suggested in the Plant Empowerment book – but it’s often that final 10% that will make all the difference. In our small-scale trials, I’ve had the freedom to try things out in a real-life setup and I’ve been impressed by the results. So I hope that this will give other growers the confidence to go for the full 100%, even if it goes against their own instincts,” he concludes.