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irrigation

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In Next Generation Growing, everything revolves around the needs of the plant. In the past, much of the way growers controlled the climate was based on green fingers and experience. But with the latest developments in greenhouse technology, the indoor climate has become a more complex factor. This also makes the relationship between conditions outside the greenhouse, the growing climate on the inside and the impact on plant growth less straightforward. The combination of plant monitoring and an advanced control system helps the Dutch company Van de Berg Roses to better match their irrigation to the needs of the plant.

Hoogendoorn Growth Management researcher Jan Voogt differentiates between three plant balances: the assimilate balance, the energy balance and the water balance. All three need to be in balance to achieve optimum growth. If you only factor in the energy from the sun and not the rest, then you’re not doing your job properly, he believes. He recognised that growers who work with lighting didn’t like the fact that they couldn’t input the energy they added from the lighting into the climate computer. And the same was true of the other factors that play a role in the energy balance.

In response to this, Hoogendoorn developed a new monitoring and control system: PlantVoice. This software module focuses on all three balances and takes the plant’s activity into account. Other factors apart from sunlight can be entered in this system, and irrigation is primarily determined on the basis of the energy flows. “The more factors you include, the more accurately you can fine-tune the amount of water to match the energy supply to the plant. That also gives you more control over the root environment and less unnecessary return water,” Voogt says.

First users

Van de Berg Roses has a 12 hectare rose nursery in Delfgauw, as well as sites in Naivasha in Kenya and Kunming in China. Maurice de Ruijt, cultivation manager at the company’s Dutch site, has been using PlantVoice for the past eighteen months. “We were pretty much the first users,” he says. “We used to irrigate based on our outdoor sensors which measured the amount of sunlight. We use a lot of artificial light here, so that wasn’t particularly helpful. We told them that we wanted to irrigate based on the PAR sum. The new module is a much more reliable measure of conditions in the greenhouse.”

PAR sum

De Ruijt had already been indirectly watering based on the PAR sum via the LetsGrow system, which had given him quite a bit of experience in this method of irrigation. He uses the measured PAR sum to determine when to start irrigating. Since he started using the new software module, he has started irrigating at the point when he measures a radiation sum of 10 mol/m2 after the last cycle. He knows from experience that the slab will have dried out by around ten percent by then. This point is reached between 2 and 6 am. He doesn’t want to start any earlier or later.

De Ruijt: “The start time can vary by a couple of hours. There could be various reasons for these variations. We can switch our lighting system on in three stages: 33, 66 and 100 percent. Sometimes we use 66 percent for a while.” What’s more, the outdoor conditions can vary after they have stopped irrigating. “Like if it’s a cloudy day but the cloud cover breaks up after you finish watering, and then you have an hour or two of sunshine.”

He waters around eight to ten times a day, stopping at 3 pm. De Ruijt still decides how often to water based on the PAR sum. For the time being he isn’t using any other factors such as the energy given off by the heating pipes to decide when to start watering, as that is more complicated and the amount of energy is negligible.

Results

Also important, of course, is what this method of climate control can deliver. “We can see that the plants have nice white roots. The crop is healthy and we’re getting better yields.” De Ruijt won’t reveal any more than that. Using the module to control irrigation is a big step in itself, but the company has also made other changes to its irrigation regime. And this, too, is part of a greater whole. “It’s a great tool to work with. It was tricky to find the right settings to begin with, but now that we’re used to it, it works really well.”

More reliable trials

Bram van Haaster, trial manager at Wageningen University & Research in Bleiswijk, the Netherlands, has been using the new module since the summer. He looks after the vegetable, flower and pot plant crops in the trial greenhouses. For the research it’s important to keep the climatic conditions around the plant as stable as possible and to only allow the factors being studied to vary.

He used to control irrigation based on outdoor radiation, the amount of drain water and instinct. That was tricky because the percentage of drain water fluctuated. Now he keeps an eye on the energy balance using sensors and data from the climate computer. He measures the amount of radiation in the greenhouse with a PAR sensor above the crop. He can input into the computer how much energy he is adding via the pipes and whether or not he is screening. In this case, energy input from the heating pipes is left out of the equation as it is a constant, low factor. “If the heating were to fluctuate, we would need to take that into account,” Voogt adds.

As a control, he uses an IR sensor that measures the plant temperature. Any rise in the plant temperature is a sign that the plant is not transpiring enough. In that case, he needs to adjust the irrigation or reduce solar radiation levels.

First experience

Van Haaster gained his first experience with this system in the summer, in a pot plant trial in which various substrates were tested alongside each other. Now a tomato trial under LEDs is underway, comparing various varieties and studying the effect of adding, or not adding, extra steering light in the form of long-wave red radiation. The light is on between midnight and 6 pm. The trial manager has been aiming for a stable drain percentage in both trials.

At this time of year, van Haaster mainly uses the PAR sensor to measure the light from the LEDs. “The outdoor light is around ten percent at best at this time of year. The increase in joules is easy to track on the computer,” he says.

On the screen he points out a neat, constant line representing the amount of drain water. Since he started using the module, the drain percentage has been stable. “If you don’t have to do much adjusting afterwards, that means you have got the settings right,” he says. “The root zone is nice and stable, both in terms of water content and EC. That’s good for the research, but it also benefits growers. You become more aware of your plants’ needs so you can get more out of them.”

Summary

With recent developments in greenhouse technology, the indoor climate has become more complex and more factors are influencing the plant’s energy balance. And that in turn impacts on the water balance. A software module is the answer. PAR sensors inside the greenhouse measure the amount of radiation in the greenhouse, and other energy factors such as the heat from the heating pipes, the screening factors of screens or coatings, diffusion and ventilation factors can be added in. Altogether they produce a better picture of the plant’s energy balance and therefore its water requirement.

Text and images: Marleen Arkesteijn.

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Higher lighting capacity, new diffuse glass types and intensive screening are developments that are having a major impact on irrigation strategies. Plants themselves can do a good job of telling us how well they are doing, as long as we start with the right combination of measurements. A short refresher course can give that little push to get even better results.

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The increase in scale that has been taking place over the past ten years calls for a different way of watering. Including on the technical side – after all, how do you make sure all the plants in those long rows are getting enough water? Can you even get it all the way round? Systems are being designed for pressure loss and pumping capacities are being ramped up. What’s more, growers are opting for drip hoses with a smaller diameter. And all with the aim of getting the water and the nutrient solution to the plants faster.

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Most growers in the Netherlands start increasing the dosage of irrigation water in April, which can cause serious problems in the watering system. That’s precisely what happened at the Varekamp-De Zeeuw tomato nursery in De Lier (Westland), where in 2016 they found themselves faced with blocked drippers. The damage to the crop was considerable, with plants starting to wilt. So they set out in search of the cause and a solution.

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With a little more effort you can improve even more. This is the approach behind new trials aimed at optimizing water and fertiliser use with the specific aim of reducing fertiliser emission to the environment. It sounds rather demanding until you realise that the quality of the end product can also improve, while maintaining or even increasing yield. Excess drain as an insurance policy for the cultivation is an out-dated idea.

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Agro-Invest’s new 20 ha greenhouse, located in the Kaluga region of Russia, has successfully completed its first growing season. This is the first stage in a project which will ultimately comprise a total of 100 hectares of greenhouse on 238 hectares of land. The Kaluga region is a special economic zone, located around 300 km from Moscow. The local government is committed to improving the diversification of the region’s economy with the cultivation of tomatoes, cucumbers and leafy vegetables. This greenhouse complex will make a tangible contribution to the region’s goal of becoming self-sufficient in the production of vegetables in the longer term.

Mr. Evgeniy Gorlach joined Agro-Invest in July 2014 to coordinate the greenhouse construction project in the Kaluga region. At first there was nothing but an empty field. Now, less than 18 months later, the company has completed its first growing season and started the second season of cucumbers and tomatoes in the new greenhouse complex, which was built in record time: just one construction season.
The greenhouse comprises 10 ha for the production of tomatoes (four varieties: one beef tomato variety, one truss tomato variety and two varieties of cherry tomatoes), 8 ha of cucumbers and a 2 ha propagation area for young plants and seedlings, plus a packing area/irrigation room and an energy building.

Specific expertise

Headquartered in Moscow, Agro-Invest operates numerous farms in Russia and its business activities include land, crops, livestock farming, equipment, technology and logistics. In his role as Technical Director, Gorlach was tasked with coordinating the project together with Dutch company Dalsem – a company specialised in the development and realisation of complete high-tech greenhouse projects – and the Russian sub-contractors.
The first point of contact for him and everyone else on the project site was Dalsem’s Maurits Zomer as Project Supervisor. “He virtually moved to Russia to work on the project – I think he spent just three weeks back in the Netherlands during the whole year,” recalls the Technical Director. “Although I’d worked on many similar projects in the past, I had no specific experience in greenhouse construction. We benefited tremendously from the expertise of Zomer and his colleagues in terms of greenhouse building and quality control of sub-contractors.”

Complete solution

In addition to the greenhouse framework, the Dutch high-tech specialist provided Agro-Invest with a complete solution for the greenhouse facility, including all machinery and equipment for the installation of the cold storage and the loading and discharge section. The growing area is fully equipped with a heating/climate control system, high-pressure fogging, roof sprinkler system, substrate irrigation, substrate cultivation, CO2 dosing, overhead (1,000W) and intermediate (250W) lights and screens. The propagation areas are equipped with aluminium rolling benches and ebb and flood irrigation.
Power is generated by four Rolls Royce Gensets of 9,285 MW each, two of which are equipped with selective catalytic reactors for the production of CO2. Additionally there are four hot-water boilers with a capacity of 11.6 MW each. The water management system also includes rainwater collection, reuse of drainage water and purification of well water.

Tight coordination

“One of our biggest challenges on this project was to complete everything on time,” comments Gorlach. “We had a very tight schedule so we worked in parallel with the project institute, which meant we made a start on the construction work for greenhouse as soon as we obtained the drawings from Dalsem. This created quite a stressful situation because we ran into various problems, such as due to the soil and a lake which meant that we had to recalculate the foundations as we went along. Later on in the project, we were particularly under pressure to get the pipework for heating finished and the water circulation system in place so that the pipes wouldn’t freeze when the first snow arrived – which is usually late November – so work started on the boiler room before all the sandwich panels were finished. We wasted no time; for example, the small irrigation room was finished on a Monday, and the tomato seeds were planted in the cubes on Tuesday – the very next day,” he recalls.
“And we even conducted ‘real-life testing’. We were testing the systems when seeds were already on the table.” This tight coordination was the key to fast completion of the project, which took less than eight months for the construction part. “No one else in Russia has ever achieved that so quickly,” states Gorlach. “It’s thanks to such terrific collaboration between all of us, including our sub-contractors, that the preparation and building work ran relatively smoothly and was completed in time for the growing season as planned. I’m also grateful for the tremendous help we received from the people at our sister companies within the holding.”

Multiple language options

The climate management system plays an important role in the control of all processes in the facility. “From an efficiency perspective, it’s important for us that everything can be managed in one, single system,” says the Technical Director. Based on the flexibility, reliability and user-friendliness of the system, the project group made a conscious decision for the iSii climate computer from Hoogendoorn, an international developer and supplier of automated climate management, water management, energy management and data management solutions for horticultural businesses.
“The system controls literally everything in our greenhouse: climate, irrigation, CO2, ventilation windows, screening and energy consumption. Everything is connected to Hoogendoorn, without it, nothing will work.” he adds. All the settings of the new climate computer are flexibly configurable. Furthermore, thanks to the multiple language options, the Dutch crop advisor and the Russian managers can log into the system and adjust the settings in their own respective language.

First-season results

“We received a lot of help with the program settings as well as local training for our employees to help them select the right parameters. The contact was very intensive,” continues Gorlach. The system went live at the end of November 2014 so that the first plants could be irrigated. “Because the system is so comprehensive, the software is very complex so there were a few teething troubles. But we were helped remotely from the Netherlands, and if necessary we received on-site support. In one case, we needed a spare part and a specialist from Dalsem flew in to Moscow and delivered it to our greenhouse on the very same day. You can’t ask for better, quicker and more flexible service than that.”
Despite it being such a whirlwind project, Agro-Invest can look back on the first season with satisfaction. “Apart from the teething troubles, we had no major problems during our first year. A manager from Hoogendoorn recently visited us to answer all our practical questions based on the first-season results and to help us to further optimise the precise settings, so we’re now ready to achieve maximum results in our second season,” he concludes.

Summary

Agro-Invest’s new, high-tech 20 ha greenhouse in the Kaluga region of Russia was constructed in record time thanks to tight project management and excellent collaboration between all members of the project team. The climate management system controls everything in the greenhouse, from irrigation and CO2 to ventilation, screening and energy consumption. Following on from a successful first growing season of tomatoes and cucumbers, the second season is already underway.

Text: Lynn Radford