Paul Jeannet, farm manager of the UrbanFarmers rooftop greenhouse in The Hague, has used the Qlipr system for three months in four different crops: ‘It’s very easy to use, once you get used to it. It allows us to save time and - this is the biggest advantage in my opinion - we can reuse the clips after every crop cycle. We can easily separate the clips from the plants and compost the plants, because there are no strings or plastic clips left in it. Nothing is wasted.’
The Qlipr system fits right into the UrbanFarmers philosophy, which is based on creating added value and minimizing waste. At the UF002 farm in The Hague, consisting of a greenhouse with a surface area of 1,000 m2 on top of a former office building and a Tilapia fish farm, that philosophy has been taken into practice. The waste water of the fish tanks is turned into nutrients for the plants in the greenhouse. In the greenhouse, different varieties of lettuce, tomatoes, cucumbers, sweet peppers and aubergines grow in a hydroponic system. The water that is not used by the plants is purified and pumped back to the fish farm, which reduces overall water usage by 80%. Pesticides are forbidden; only biological plant protection methods are allowed. The products are sold to customers in the region, to minimise food miles. ‘We grow fresher, tastier and healthier products, as close to our customers as possible. And we minimise waste,’ Paul Jeannet explains.
The fresh revolution
Paul Jeannet (24) started working for Urban Farmers one year ago, after an internship at UrbanFarmers’ first farm (UF001) in Basel. He studied biological agriculture in Switzerland, before he joined ‘the fresh revolution’. ‘At first we were only growing lettuce and tomatoes. When our gastronomy partners told us that they would prefer more diversity, we took out some of the tomatoes and put in cucumbers, aubergines and sweet peppers instead, and several different varieties of tomatoes. We kept the lettuce section.’
It is quite different from the normal plastic clip we were using, but once you get used to it is very easy to use.
Six months ago Paul got in touch with Cor Pellikaan and became interested in the Qlipr system. ‘We wanted to give it a try to see if it would work in different crops. Three months ago we started using the system in tomatoes, cucumbers, sweet peppers and aubergines. As it turned out, the system is quite easy to use: we take the lower clip and place it on top and we lower the plant at the same time. It is quite different from the normal plastic clip we were using, but once you get used to it is very easy to use.’ The lowering schedule is once a week for tomatoes, three times every two weeks for cucumbers and once every two weeks for sweet peppers and aubergines.
Cor Pellikaan, the inventor of the Qlipr system, needed a pilot project to test his clips on sweet peppers and aubergines. Until three months ago, the system - which he invented in 1996 - was only used by growers of tomatoes and cucumbers worldwide. The system consists of a crop hook (1.40 meters long) and two clips. Halfway through the plants’ development, extra crop wires are needed with which to fix the crop hooks into place.
It will save labour, because you can de-leaf, remove shoots, prune and lower the plants in one go.
The main advantages of the system are, according to Pellikaan: ‘It’s very simple to use. Everybody can work with it. It will save labour, because you can de-leaf, remove shoots, prune and lower the plants in one go. This is also better for plant health, because there is less chance of damage.’ Paul Jeannet confirms that he saves up to six hours a week in the rooftop greenhouse because he uses the Qlipr system instead of regular plastic clips.
The main advantage of the Qlipr system is its durability, says Pellikaan. ‘My first client bought them 18 years ago and he is still using the same clips. Of course, you have to disinfect them at the end of every crop cycle, but that is very easy. You can use steam, chemicals or pasteurization. I recommend the latter, after two years of thoroughly testing this method. Just put the clips in a box on a trolley and cover it up with a canvas. Heat up four pipes to 60°C under it for three days. Works perfectly.’
Thanks to the Qlipr system neither plastic string nor clips are left on the plants after each crop cycle.
Paul says this is a big advantage too, but there is more. Thanks to the Qlipr system neither plastic string nor clips are left on the plants after each crop cycle. ‘So we don’t have to throw away our plants, but we can shred them for composting. It also makes it much easier for us to get rid of the plant material, because we have to transport everything via the lift.’
Qlipr versus traditional clips
How many clips are needed to bear the weight of the plants? ‘At the start of the season one clip will suffice. You attach it at 40 cm below the head of the plant. When the plants get heavier you will need to add a second clip, Cor Pellikaan explains. A new item in the Qlipr product range is the double-stop crop hook of 1.40 meters with two stoppers: one at 50 cm and one at the bottom of the hook. This makes it possible to use the same hook for tomatoes as well as cucumbers.
You buy it once and then you can use it every year.
The investment in the Qlipr system is higher than with traditional plastic clips, but they will last a lifetime, Cor says. ‘Also, you don’t need to buy expensive trolleys with hydraulic platforms, because the plant tips grow at a height of 160 cm. Therefore, cheap trolleys will suffice. In most cases this will save you enough money to buy Qlipr clips.’
Paul Jeannet has become a fan of the Qlipr system rather quickly: ‘Cutting leaves has become more enjoyable. We no longer have a plastic string or plastic clips at the bottom of the plant holding the leaves together. Only two clips at the head of the plant.’ Would he recommend this system to other growers? ‘Yes! It is a really interesting system to work with; you buy it once and then you can use it every year.’
Pellikaan thinks the Qlipr system will also benefit growers in the future. He is working on a mechanical system to pollinate crops without the use of bumblebees. It has been tested thoroughly and he expects to launch it this year. He is also working on a robot that can harvest and de-leaf tomatoes, which is still a prototype. That is still a bit of a secret, so we will stop asking here. It is clear that Cor Pellikaan is still coming up with new inventions for international horticulture to create simple solutions that work.
Energy efficient production according to the principles of Next Generation Growing, without any additional investment, is the aim of pepper trial being carried out at the Delphy Improvement Centre (IC), Bleiswijk, the Netherlands. Armed with two energy screens and fans the trial participants want to save 30% on energy and still achieve good fruit quality.
The main barriers raised by pepper growers to grow as energy efficiently as possible in practice are doubts about the impact on crop health and fruit quality. This therefore was the reason for running two climate trials this year with peppers, one at the Improvement Centre and the other at neighbouring Wageningen UR Greenhouse Horticulture.
The one at the IC is being carried out in an area covered with a standard greenhouse roof and two energy screens. The other trial is taking place simultaneously in a VenlowEnergy greenhouse with double glazing. The red variety Maranello was planted in both greenhouses on 7 December 2015. A Supervisory Committee, which includes four pepper growers, is following the trials closely.
The trial at the IC uses two transparent energy screens, namely Luxous 1547 D FR and Luxous 1347 H2no FR. The H2no property ensures that when the screen is used during the day it also allows a lot of light to penetrate even when it is wet due to condensation. In addition the area is equipped with horizontal and vertical fans and is sparsely heated. Although the energy consumption on commercial nurseries is usually about 30 m3 per m2 the trial participants are aiming for 20 m3 per m2. That is a saving of more than 30%.
Assessing the balance half way through the trial it would seem that the goal is achievable. Energy consumption is even slightly lower. Maximum use of the energy screens and omission of the minimum pipe rail therefore have a huge impact.
Screening based on radiation
The principles of Next Generation Growing (NGG) were applied during the trial. The use of the energy screens is the dominating factor. The upper screen opens when the radiation is 100 watt per m2. The second screen opens at the moment that the temperature above the screen differs by four degrees from the desired heating temperature. This small difference should prevent a cold dump.
There were moments this spring that the lower screen was still closed when the radiation was 300 to 500 W/m2. The intensive use of the screens has, from the start of the cultivation to early April, led to 14% light loss. That was difficult for the growers to get used to as they prefer to allow in as much light as possible.
“But the crop was growing to our liking,” says Rick van der Burg, crop manager at the IC. “We noticed that the room temperature was quickly a degree higher than what is usual in practice," adds Arie de Gelder, researcher at Wageningen University & Research.
Drain off moisture
At the same time the screens play a major role in the removal of moisture. At the moment that the RH becomes too high, cool dry air is supplied via the vents above the screens. The moisture is then removed to the outside via transport through the screens. Therefore the usual method of making a gap in the screen is not used,
The fans ensure a uniform temperature and moisture distribution in the greenhouse. At the start of the cultivation this was achieved by just using the horizontal fans. As the crop becomes taller the vertical fans are used too.
The trial participants are not completely satisfied with the air currents and thus the temperature distribution that occurs in the section. Bubble wrap is attached to the walls to rule out influences from outside and from the adjacent much warmer section. Because so little heating is used the temperature differences between the walls has relatively large impact. “We’ve noticed that strong air currents occur,” says De Gelder. That will be different in a practical situation.
When Van der Burg made the first assessment in mid April, it revealed that 2,500 hours of screening were with a double screen. That saved a lot of energy especially in March and April.
A net radiation sensor was hung in the top of the greenhouse. This shows how much radiation enters the greenhouse and how much radiation is emitted from the crop. The double screen in the night leads to an important reduction in the radiation emitted.
Screen out the light
As the radiation increases, the screens will be used as a tool to screen out excessive light. The greenhouse does not have a solar reflective coating. When the radiation is more than 700 W/m2 the upper light diffusing screen closes 80% and the lower screen 40%. They are positioned so that they overlap each other. De Gelder: “In this way we want to keep the humidity as well as the CO2 as much as possible at the right level."
Initially ventilation only happened when the greenhouse temperature was more than 27°C. Since the greenhouse temperature rose rapidly at high radiation it was decided to slightly reduce the temperature. Van der Burg: “We noticed that the fruits then become wet and we have to prevent that.”
24-hour temperature based on radiation
The desired greenhouse temperature is very dependent on the radiation. During dark periods the 24 hour temperature is 18.5ºC. When the light sum is 1,000 joules the 24-hour temperature should be 20.5ºC and at 2,000 joules it should be 22.5ºC. The light sum of the previous day determines the night temperature that follows.
It’s noteworthy that no minimum pipe rail is used. Heating is only used when there is a need for energy. Incidentally, plant temperature is well monitored.
What is now interesting is how the crop responds to these climate settings. In particular the growers in the Supervisory Commission, who are willing to push to the limits, have been amazed at the crop condition. They didn’t expect the crop to look so good after so much screening and the subsequent loss of light. During the first setting some fruits aborted so the trial participants didn’t have to consider thinning out. The first setting started to develop a little later than in commercial nurseries but the differences weren’t shocking. Harvesting started in week 12 and by week 18 the yield was 6.10 kg/m2.
The second part of the cultivation will be interesting when the radiation rises even higher and the crop develops further. Then the emphasis will be more on the vertical temperature distribution in the greenhouse. Of course the growers and researchers are closely following the quality of the fruit. Everyone is wondering what the final fruit quality will be like and what affect the climate regime has on the total yield.
A pepper trial with NGG in an existing greenhouse in the Netherlands shows that during the first half year a lot of screening has no adverse effects on the crop or yield. Up to now it has been easily possible to save 30% on energy. The two energy screens limit the radiation during the night so the crop temperature remains higher.
Text and images: Pieternel van Velden
Sweet peppers arrive in waves. New fruits lure so many assimilates towards them that the flowers above them abort. This article provides various suggestions about how to flatten out the peaks and troughs. In the long term, breeding can also play an important role.
If you want to read this content you need a subscription, or log in when you already have a subscription.