"It turns out to be more vigorous than expected" is a phrase many tomato growers might find familiar. Cultivation advisor Willem Valstar of StarGrow Consultancy often hears it, especially as growers begin cultivating new ToBRFV-resistant varieties. These varieties often behave slightly differently than their predecessors. But what exactly is different? Good generative and vegetative crop registration helps to clarify this. In the model-based crop planning platform ProJoules, growers can register these measurements.
"When I hear growers say things like, 'It's behaving differently than last year' or 'I feel the crop looks worse than before,' I always say, 'Let's look at the numbers.' With proper crop measurements, you're not just relying on feelings or thoughts."
The rise of new resistant tomato varieties was rapid due to urgent need. There wasn't always a lot of practical testing before growers started cultivating new varieties on a large scale. "This sometimes surprises you with how vigorous some new varieties are," observes Willem. "Although you also have very vigorous varieties that have actually become more balanced after the introduction of resistance. Such varieties have become more generative and productive.
Measuring and registering length growth weekly remains important.
Building data
Breeding companies provide growers with information about how a variety grows and behaves under certain cultivation conditions when delivering new varieties. In ProJoules, variety profiles are now automatically available for growers. However, the information from breeding companies is generally not as detailed as one might wish, states Willem. "You're often happy just to hear from the breeder that a variety is more vigorous. Exact plant parameters are not always available."
By doing crop registrations, growers can build up detailed data in systems like ProJoules. Growers are doing this, Willem sayss. "Both young and old, although you definitely see that feeling plays a lesser role among younger growers. They want the numbers."
No discussion
The cultivation advisor registers the plant measurements in Excel. There are also different systems where it is possible to do online registrations, including ProJoules. Growers also actively compare this data among themselves, according to the advisor's experience. "Field trips have really made a comeback since COVID. Maybe not as often as before, but it does happen, regularly online too."
Growers are increasingly sharing videos, but not everything is clearly visible in them. Willem estimates that seventy percent of problems can be solved by just looking at a video, but for the remainder thirty percent, you really want to see the crop in the greenhouse. "There you observe and measure, for example, that the heads are thicker and the leaves are longer in some resistant varieties. You can also see that with the naked eye, but the beauty of capturing it in numbers is that there can be no discussion later. If the ideal head thickness is 10 millimeters, then it's not 9.5 and not 10.5 either."
The stem diameter also provides a lot of insight into the vegetative and generative development of the plant.
Production per light unit
Last spring in The Netherlands was darker and wetter than usual, which proved to be a challenge for growers. "You could see that production went down." The question is then why is that. The first suspect is of course the reduced light availability. "There was a significant light deficit," says the advisor about the situatie in The Netherlands. "But if you convert that to production per light unit, then you'd notice that overall production stayed the same as last year. Of course, comparing the same varieties year after year it's easier. In fact, new varieties sometimes can be less productive."
As an explanation for the somewhat surprising conclusion after converting production to light unit, Willem indicates that the Dutch spring was also less warm. "Too warm is generally negative for production. Another advantage is that, because it was often cooler, you could also keep the CO2 in the greenhouse more easily."
Measuring leaf length provides information about the development of the plant.
Maintaining balance
Growers work with different systems, Willem sees. He himself calculates production per light unit himself - which is something that ProJouls can also calculate for growers, but not all systems can, Willem knows.
ProJoules is a model-based crop planning platform where growers can also add crop registrations. The crop planning platform is developed with a focus on Joules, or rather: the total sum of light energy in the greenhouse at plant level. The generative and vegetative crop measurements growers make can be linked to other cultivation data in ProJoules. This allows for a better comparison between vegetative and generative plant development. This contributes to a much faster development of a desired crop profile, where the grower and advisor together set upper and lower limits on growth, stem thickness, flowering height, and leaf length, among other things.
"On the one hand, as a grower, you need to ensure that the light requirement and cultivation speed are balanced, and on the other hand, the plant itself must also be balanced," explains the cultivation advisor. "Not too generative and not too vegetative." Both balances are equally important. "You can have the light requirement, cultivation speed, and temperature in balance, but if the plant is too generative or too vegetative, you will still not achieve your production goals in the long run."
The optimal setting is best achieved with a plant that is balanced.
Lessons on moisture
Anyone who concludes that the cultivation is not balanced at this point in the Dutch unlit cultivation season faces a significant challenge. "A little adjustment is possible, but completely straightening things out is not anymore, sadly."
Willem sees that lessons have been learned from last year, such as dealing with moisture in in as energy-efficient a way as possible ."Last year, there was a lot of moisture. You see this reflected in crop and climate registrations. However, this spring was very wet, and that caused problems here and there. In some companies, Phytophora and mildew crept in and things went completely wrong."
Energy-efficient cultivation one year is not the same as the next. The combination of a wet spring and energy-efficient cultivation has reached the lower limit. "You shouldn't go too low in the energy you put into your cultivation., it's just not really business savvy. You can't base a cultivation on such a thing. We now know how much moisture in the greenhouse we can roll with." Putting a hard number on it is difficult. "Some areas are more humid than others. Where one grower is happy with a moisture deficit of 1.5-2, another is happy with 1-1.5."
Dealing with moisture remains challenging, especially in tomatoes, the cultivation advisor says. "In tomatoes, you deal with a full crop faster than in, for example, bell peppers. If you keep cultivating too moist, you also have problems later in the year." Thing is, energy is necessary to get rid of moisture, and that's where dehumidification systems come into play, says Willem. "Using them may be quite energy consuming, yet you can easily get rid of humidity, thus allowing the crop to become generative. Just check your crop measurements."
Willem: "It'd be ideal to have camera systems taking over plant measurements in the future. Alas, we're not there yet. AI systems also still rely on manually entered, human data."
For more information:
ProJoules
[email protected]
www.projoules.com
StarGrow Consultancy
[email protected]
www.stargrowconsultancy.nl