organic
Ability to differentiate through use of organic substrate
Tomato Masters, of Deinze, Belgium, is producing tomatoes on an organic substrate in response to a discussion with its retail client. Now the cluster tomatoes are promoted in the store as a tasty local Belgian product ‘grown in rich ground’. Crop manager Tom Vlaemynck explains the difference between production on rockwool and an organic substrate.
Tomato Masters was founded in 2012 and in the meantime has acquired the entire designated horticultural zone of 36 ha in Deinze, East Flanders. The company is run by the brothers Herman, Dirk and Johan, Tom (Dirk’s son) and Tim (Herman’s son) Vlaemynck. They originate from Poesele, where they still have a nursery of 3 ha and where their history goes back to 1966. However, that location was too small for five managers so they decided to extend some 12 kilometres further away. At the moment this comprises 10.5 ha of glasshouses so there is space for considerable growth.
The large cluster tomato Merlice is grown in Poesele. Plum, cherry and middle-sized cluster tomatoes of the tasty variety, Foundation, are grown in Deinze. The latter is produced on the organic substrate (6.3 ha), the other varieties on rockwool (4.5 ha).
Keep plants generative
The growers already had experience with the organic Greenyard Grow Bag at the old nursery. However, when Tom Vlaemynck joined and had responsibility for the cultivation they went back to rockwool. “I didn’t want to take any risks; I knew all about rockwool. Also, we weren’t maximising yield on the organic slabs,” he says.
Meanwhile, thanks to a joint effort with the supplier and crop advisor, Jos Christianen, it became clear how that could change. “The start of the crop is completely different to a crop on rockwool and because we gave the plant too much water at the start it remained vegetative,” he says. “When using rockwool you use the dripper to fill the slab at the start with 20 litres; it is completely different when using an organic substrate. Then you start with just 3 litres. After that you drip through the pot that you immediately put into the planting hole. If you approach it this way you can keep the plant generative.”
Research is being carried out by the provincial research centre for vegetable production (PCG) in East-Flanders, Belgium, to establish the right strategy at the start of the crop, says Hans Baekelmans, of the substrate supplier. “The weight of the rockwool slab has to drop at the start of the cultivation before you start to drain. The weight of the organic substrate should remain stable. It’s a completely different way of production,” says the grower.
Fast start
Another important difference is the labour requirement for planting. When using the Grow Bag the plants are immediately placed in the plant hole and supported by sticks that are inserted next to them. When using rockwool the block is firstly placed next to the hole and afterwards moved into the hole and supported with sticks. Thus the work is spread over two works shifts. “At first we weren’t quite prepared for a higher labour peak but if you know in advance you can plan for it,” says Vlaemynck. “In total it doesn’t cost any more work. And it’s noticeable that fewer plants fall over than on rockwool.”
Because the plant is placed directly in the hole it produces more roots faster. “It gets off to a very quick start,” he says. You can pick up real speed after the second cluster whereas on rockwool you have to be restrained for a little longer,” he says. However, despite the flying start he wasn’t able to achieve a higher yield. That could have been due to the conditions during the spring of 2016. “The weather didn’t help at the start of the crop. Perhaps you’d gain more from the larger root system if there was a lot more light,” he says.
Authentic products
He didn’t notice any difference in the quality of the tomatoes grown on the two types of substrates.
The Grow Bag comprises peat pellets with a small fraction of cocopeat wrapped in foil. The material is recyclable. “It’s turned into peat compost for use in the gardening sector,” explains sales manager, Els Thoelen. “If you remove the foil you can sell it because the product still has value.”
The fact that this is organic material and is recyclable means that the substrate complies with Carrefour’s FQC-label (FQC = Filière Qualité Carrefour). This label promises to supply consumers with an authentic product of good taste and constant quality produced with respect for the environment in a sustainable relationship between buyer and producer. At the moment five vegetable producers can carry the FQC label: In addition to the cluster tomatoes are asparagus, open field chicory, potatoes and special carrots grown on loamy soil.
Special specifications
The retailer’s interest in crops from soil (in this case potting soil) was the decisive factor for the growers to choose an organic substrate. On the other hand they receive a small extra price for these tomatoes. They are presented in boxes in a single layer which has space for nine clusters. A label on the box describes why the tomatoes are so special and the photo of Tom Vlaemynck shows where they come from. He also plays the leading role in a promotion film that is shown in the stores. And so he is gradually becoming a well-known Fleming.
The label requires compliance with a special set of specifications. As well as the points already mentioned it is necessary to keep a record of the amount of water and chemical substances used. The nursery uses only rainwater and biological crop protection. No chemical substances have been used since planting.
To achieve the right taste and quality Vlaemynck uses a relatively high EC in the drip irrigation at the start of the crop. “Even in the summer we don’t drop to a very low value. Therefore we use a lot of water with a relatively high EC so that the quality remains better. We collect all the excess water.”
Soil resilience
An organic substrate can more quickly develop a very varied soil life that encourages plant resilience. This can be a tool to combat against crazy roots and was the reason for a large Dutch tomato grower to recently switch to these grow bags. However, crazy roots were not a problem for Tomato Masters. The grower does pay attention to soil resilience and after a discussion with Koppert Biological Systems decided to add Trichoderma to the substrate; this fungus colonises well in the organic environment.
All-in-all Vlaemynck finds growing on an organic substrate very similar to production on rockwool except for the initial period when a completely different approach to watering is needed.
Summary
Tomato Masters, of Deinze, Belgium, grows a large proportion of its tomatoes on an organic substrate because this is of extra value to the customer who sells the product under a special label. In the beginning the substrate requires a completely different watering strategy to rockwool but after the first phase there is little difference in the cultivation. In future it may be possible to gain more from the fast growth at the beginning.
Text: Tijs Kierkels. Photos: Wilma Slegers
Phalaenopsis grower opens the batting with certified organic production
GreenBalanz, of Kudelstaart, is the first Dutch pot plant grower to introduce organically grown phalaenopsis to the market. Although it is still a small number and a modest range, grower Lennard van der Weijden has full confidence in the production and marketing. However, the market still lacks a supply of other organically grown pot plants.
In 2009 Handelskwekerij Van der Weijden was renamed GreenBalanz. This was to underline the sustainable character of the company and allow the owner to better differentiate his company on the market. “We have a greenhouse without gas, we work with natural crop protection products, we use heat pumps and green energy, recirculate our water and do whatever possible to grow as cleanly and responsibly as possible,” he explains. “Our carbon footprint is therefore very modest. In addition, we conduct an active social policy because this is part of our corporate social responsibility.”
Despite all efforts to make the business more sustainable, in 2008 a Swiss customer felt that things should go a step further. “To be able to call ourselves really green the customer felt we should also grow organically,” says the grower. “That meant no chemicals and only organic fertilisers. The buyer wanted us to do this even if it was just in part of the nursery, because then the retail chain Coop – the client in question – could also differentiate itself better.”
Long search
Van der Weijden picked up the gauntlet but soon realised he was going to have invent the wheel himself. Apart from encouraging words, breeders, substrate suppliers and knowledge centres had little to offer that could give him some tailwind. “Apart from biological crop protection, which we were already using, biological cultivation of orchids was completely virgin territory," he says.
The grower did not give up and instead started years of searching for a solution in which plant nutrition stood and still plays a central role. Two factors raised hurdles: the long cultivation period of orchids and the poor growth medium, which is almost completely composed of bark.
Conversion process
“Phalaenopsis is a epiphyte and grows best on bark,” explains the grower. “Bark, however, has hardly any buffer capacity. For standard production that’s not really a problem because in principle all nutrients can be supplied in an available form via the fertiliser. When you apply organic fertilisers, the organic ingredients first have to be converted into inorganic components. That takes a few days and really you don’t have this time. Every time you water, you flush out a large part of the nutrients that after the previous watering were converted into an absorbable form. In addition, bark is a medium with a very poor environment, without any rich soil life that can promote the conversion.”
It took years for the grower to devise the mixture of vegetable and animal manure with which he now achieves acceptable results. He makes the manure into a thin ‘soup’ in a stock container, where the conversion process also starts. Via a separate watering installation – the organic cultivation is strictly separated from the conventional cultivation – this soup is added to the irrigation water.
Slower response, longer cultivation period
The second difficult factor is the long cultivation period. Van der Weijden: “You can try new things and push many different buttons but the results are only visible in the plants five to six months later.”
The limitations imposed by the use of organic fertilisers and the necessity to keep the crop as generative as possible during the hardening off phase does, however, force a steady cultivation regime.
“The quality is no less than that of conventionally grown plants but a completely organic production takes at least three months longer,” says the Dutchman. For that reason he purposefully limits the organic range to the strongest growing varieties. Depending on the progress that is being steadily made the assortment will certainly be expanded.
Quality mark
It is clear that the development of a profitable organic cultivation method requires infinite patience and cannot be carried out on a large scale. In 2014 Van der Weijden eventually reached the point that he was returning reasonable production results that met the official Dutch guidelines (SKAL). “It took a lot of time and energy because initially SKAL did not want us to source material from meristem culture,” he says. “Fortunately, after two years we got the green light, otherwise I’d have thrown in the towel.”
Share my experiences
The first organic phalaenopsis plants were launched on the market early in 2015. In addition to Coop, which loyally stuck to its promises, the grower also supplies other highly-positioned supermarket chains and garden centres in Europe. Although demand is still growing, the share of organic production on the nursery is still less than 10 per cent. It is understandable that it isn’t storming along due to the higher cost- and sales price. However, the market potential is far from fully exploited.
“Over the last 12 months I've spoken to several buyers who would like to sell more organic products than just phalaenopsis,” says the grower. “They find the offer still too narrow and therefore remain reticent.”
When prompted Van der Weijden says that he has not yet been approached by growers who want to copy his initiative. “That surprises me. I am happy to share my experiences with growers who sincerely want to make a start with organic production. Such cooperation can mutually benefit both partners. But it’s logical that I’m not waiting for other phalaenopsis growers to come along. With more of the same we won’t raise the entire organic segment to a higher level.”
Learned a lot
If colleagues join or not, GreenBalanz continues to search for further optimisation. Trials are running with fertilisers, plant improvers and preparations and new varieties are continually being tested.
“We still have a lot to learn,” says the green grower. “What I find very positive is that this project has also yielded a lot for the conventional crop. For the last two years we haven’t had to treat the entire greenhouse for mealybugs, because due to our approach in the organic section we were overall more alert and scouting was more intensive. Previously it was an ‘effort’ that no one looked forward to. Now it is a responsible task with clear added value, which two employees really enjoy doing.”
Another change that has been implemented throughout the nursery is the disinfection of auction containers by placing them in a freezer cell for 24 hours at -20ºC before and after use. The containers are an important contamination source of aphids but the insects can’t survive a temperature of 20 degrees below. “Actually the auction should do that itself, now we do it,” says the grower. “Fortunately it brings us significant savings.”
Summary
After years of searching, GreenBalanz, of the Netherlands, has developed a workable method for the organic cultivation of phalaenopsis. Grower Lennard van der Weijden hopes other pot plant crops will follow his initiative. He argues that some retailers find the supply of organic pot plants still too narrow to include in their range.
Text and images: Jan van Staalduinen
Agrosol profits from high-tech year round production
Spain is – perhaps wrongly – still often seen as a country with middle-tech greenhouse horticulture: that is crops grown in the open ground, only protected by plastic stretched over wooden poles and the sun, however positive, as the most important growth medium. However, that is changing. In southern Spain more and more growers are switching towards professional vegetable cultivation in high-tech greenhouses.
Agrosol Export, of Roquetas de Mar, Almería, is one of those Spanish growers which has invested heavily in climate control, water utilisation and is introducing organic production to ensure year round harvest of quality produce. Founded in 2008, the company is owned by three families and run by eight members of the second generation. Ambitious and knowledgeable in production and marketing, they decided that their future lays in large scale, high tech greenhouses.
“Our fathers were growers and our families have been involved in agriculture in the area since the 1960s. We realized that if we could provide our clients with the same quality all year round we would be more competitive than other local Spanish producers and our traditional competitors in Tunisia and Morocco. We made significant investments in 2008 in high tech greenhouses and then again in 2012 when we installed heating pipes and CO2. At the moment we are very satisfied although we do have plans to expand further,” says José Ángel Amat, one of the directors.
Change the assortment
They have 105 hectares, including 32 hectares of state-of-the-art greenhouses, equipped with double layered plastic between which air is blown, to give a very good thermal insulation.
Initially they grew cherry, beef and snack tomatoes but one of their advantages, says Amat, is that they can change the assortment to respond to the market and client demand. “For the first four to five years 60% of our production was cherry tomatoes but over the last two years that has decreased as many other growers now grow cherry tomatoes. That changed the market. We want to be as profitable as possible per square metre so we switched over to mostly sweet peppers and cucumbers.” At the moment 50% of the greenhouses produce bell peppers, 45% long cucumbers and only 5% (8 hectares) is tomatoes.
Year-round consistency
Another change was the installation of pipe rail heating on 15 hectares in 2012. Various types of heaters warm the air in a further ten hectares. You’d think that heating pipes would be superfluous in southern Spain but after a visit to Mexico Amat says he realised their potential. “You can’t imagine the level of high technology they have there. They have pipe rail heating and I was very impressed with the quality of the fruits they were able to produce. Here the minimum temperature in winter can be 6-7ºC and at that temperature the yield of bell peppers and cucumbers decreases. And we have high humidity in the morning which has a big impact on quality.”
Therefore, in 2012 Agrosol Export commissioned the Bom Group to install a methane-fired 12 MW boiler, a heat storage tank of 3,000 m3, pipe rail heating on 15 hectares and a CO2 system in the greenhouses and at a cost of 2.5 million euro.
Further expansion
“We run the boiler, which also provides CO2, from the end of October until the spring. This year that was until the beginning of May. This has enabled us to achieve consistently high yield of very high quality. We will harvest until the beginning of August and we expect to reach a yield of 20 kg peppers/m2; 70% red and 30 % green," says Amat. The cost price is around 0.80 to 0.90 euros per kilo, compared with 0.50 euros in the hot air heated greenhouses where the yield is somewhat lower at 7-8 kg/m2.
The benefit gained from the pipe rail heating means they are gradually installing more in the current greenhouses and next summer they plan to build a new 10 hectares high tech greenhouse. “If that goes well then in about three years we may build again,” adds Amat. “We believe that investing in technology is the only way to be better than our competitors.” The new house will also have a double plastic covering but they will aim to allow in more light and it will be higher, at 7 metres, to improve air circulation.
Direct marketing
Their success can also be attributed to their marketing and relationships with their clients. Most growers in the area sell through a cooperative whereas Agrosol knows its clients directly. Its main customers are UK retailers, although it does sell snack cherry tomatoes under the brand ‘Cherrytos and co' aimed at children. These are mainly sold through Faborit, a trendy outlet in Madrid, or via e-commerce. “We want to invest a little more in the snack tomato business because we think this is a good way to gain more profit,” says Amat.
Of course they have to fulfil individual audits for their clients such as Nurture for Tesco, and comply with codes of conducts such as GlobalGap and Leaf Marque but that is part of the commitment required for these partnerships.
Trend to organic
They are also increasing the volume of organic production. “Nearly 10% of crops are organic and we are planning to increase this in future to meet the growing trend.”
In the remaining houses they use an IPM program and biological pest control suggested by their supplier Koppert Biological Systems. They have been implementing this since they started Agrosol Export and their father’s used it before that.
This allows them to minimise most of the common diseases and keep well below the mandatory maximum residue levels. “We have a highly developed pest control system which allows us to avoid a lot of diseases,” says Amat. They currently include a range of natural predators including Amblyseius swirski, macrolophus, orius and Amblyseius californicus. “We do a control at the propagator and we make continual checks at all stages of the crop to check for disease and to ensure the natural predators are well established.”
Cocopeat substrate
Over the last few years they have been gradually switching to a cocopeat substrate. Now the majority of crops are grown in this, just some in rockwool. “We separate the cocopeat from the plastic bag and recycle them both: the cocopeat is composted and we are building a plant to convert the plastic bags into biodiesel for our own use.” It should be completed within six months.
“Our strategy now is to progressively convert all our greenhouses to high-tech, in a sustainable way. This is the only way to produce high quality fruits year round and be profitable per square metre,” the grower concludes. “It is a major investment but the results are good. Our clients are very happy with our service and our ability to offer quality products during the difficult winter times.”
Summary
Significant investment in high tech greenhouses, including pipe rail heating, by large Spanish grower, Agrosol Export, is allowing it to produce consistently high quality peppers and cucumbers year round. The majority are sold to UK retailers. It has the flexibility to switch crops to market demand and is gradually cultivating more and more organic produce.
Text: Helen Armstrong. Images: Agrosol Export
Increasing range of plant strengtheners available
Manufacturers and horticultural suppliers alike have been expressing increasing interest in the development and market for plant strengtheners. A whole series of products based on substances of a natural origin, from micro-bacteria to hormones and from fungal preparations to seaweed and from algae to fatty acids, are lauded for their resilience-boosting capacities. An overview, however temporary, is presented below.
Our planet’s flora and fauna offer a wide range of substances that are beneficial to crop protection. The members of Artemis develop agents and systems that increase plant resilience to such an extent that diseases and pests simply won’t stand a chance. Artemis is the industry organisation and interest group for biological crop protection. The organisation is composed of manufacturers and suppliers of natural enemies, pollinators and plant protection products of natural origin. The substances (i.e. products) impact a wide range of functions in plant physiology.
Defence proteins
According to Alwin Scholten, cultivation advisor and owner of PlantoSys, plant strengtheners can be used in multiple ways. PlantoSys incorporates the plant-based defence protein salicylic acid into its products. Every plant produces this naturally. If the concentration is high enough, the plant starts to produce defence proteins that can block the growth of bacteria, fungi and viruses. ‘Salicylic acid is, in itself, not an antibody. It spurs the plant to produce defence proteins,’ explains Scholten. ‘However, a sufficiently high concentration must be attained in the plant before this will work. This level can be increased by administering salicylic acid to the plant’s leaves (by spraying) or roots. Stimulating the plant’s own immune system through the application of salicylic acid has proved to be highly effective in combating fungus or bacteria-related problems.’ The product appears to be highly effective against biotrophic fungi, such as powdery and downy mildew, Fusarium, rust, fruit rot (Colletotrichum) and Alternaria. It also inhibits the development of spider mites, whiteflies and aphids. Scholten recommends weekly doses as long as problems are anticipated. His product, SalicylPuur, has been approved by the Ctgb as a fertiliser. Other products developed by PlantoSys, with combinations of micro-silver and micro-copper, are marketed likewise. Scholten has noticed a growing interest among horticulturists in plant-strengthening fertilisers. ‘Four years ago the majority of the response I received was predominantly sceptical, but the sector is becoming more open-minded, particularly in the past two years.’
‘Four years ago the majority of the response I received was predominantly sceptical, but the sector is becoming more open-minded, particularly in the past two years.’
Root system
Plant strengtheners are commonly applied to the soil (the substrate) or administered as a fertiliser when watering the plant. The interest expressed by professional growers for soil and crop stimulation agents is growing, but Aly Loes Vellema of ECOstyle bv in Appelscha still has the impression that as long as chemical alternatives are still widely available, the majority prefers to stick to these. Researchers at WUR are also of the opinion that plant strengtheners are not ready to replace crop protection agents, but are a good supplement. ECOstyle focuses on ecologically responsible fertilisers, soil improvers and crop protection agents. Vellema is the supplier of the bio-stimulating soil improver Exsol P, a composite of various types of bacteria. The Bacillus combination has the capacity to free organically bound phosphates and phosphates bound to minerals from the soil, which allows the root system to develop better and the plant to better absorb water and nutrients, thus boosting overall plant resilience. ECOstyle is currently engaged in the development of plant strengthening substances, about which Vellema is not yet ready to share the details.
Photosynthesis
There are also plant strengtheners on the market that work at photosynthesis level. Pentakeep is a liquid nitrogen fertiliser that is blended with 5-aminolevulinic acid. Administration of this fertiliser causes photosynthesis to be prolonged, and as a result, the production of sugars and dry matter. Cor den Hartog of Pentagrow, importer and distributor of this originally Japanese product, has had over fifteen years of experience with the application of this product in greenhouse horticulture. Tests and studies have demonstrated that Pentakeep enhances vigour and resilience in crops. ‘Research conducted in practice has shown that crops treated with Pentakeep are less susceptible to mildew,’ den Hartog explains. ‘When applied properly, you will have a success rate of 100%.’
5-aminolevulinic acid (5-ALA) occurs naturally in plants, but its production rate depends on the speed of the plant’s metabolism. This metabolism can be accelerated by giving the plant an extra dose of Pentakeep. Plants need 5-aminolevulinic acid to produce chlorophyll. In addition to this, 5-aminolevulinic acid will increase the production of sugars and accelerate the absorption of fertilisers. The result is improved overall growth, higher production rates and stronger plants. Den Hertog confirms that Pentakeep is an NPK fertiliser and regrets that it is not yet 100% biological. The firm aims to bring a biological variant of Pentakeep to the market in the near future.
Soil resilience
On the list of the most important disciplines, Koppert Biological Systems occupies the top position with ‘resilient cultivation with NatuGro’. The international market leader of biological crop protection products has placed its resilience activities with EBIC, an international platform for enterprises engaged in the promotion of the bio-stimulants industry in an endeavour to encourage sustainable agriculture and horticulture.
Koppert is convinced that soil resilience is the key to healthy and vigorous plants.
Koppert is convinced that soil resilience is the key to healthy and vigorous plants. With a system that is composed of a diversity of products, soil analyses and expert advice, Koppert offers an all-encompassing approach under the name NatuGro. The products that are included in the NatuGro system are not stand-alone, but form part of an integrated approach: a system that enhances the biodiversity of the cultivation medium and increases the plant’s resistance to disease. A healthy and well-balanced soil life is crucial to this. Pathogenic fungi and bacteria will be inhibited because they are challenged or attacked by various groups of useful organisms in the root environment. One of Koppert’s best-known products is Trianum, a biological plant strengthener containing Trichoderma harzianum T-22 spores. While having a strengthening effect, it also enhances plant resilience in general against a variety of soil fungi. Other products included in the NatuGro system are used in the propagation stage, to stimulate root development and enhance root quality, or to improve photosynthesis.
Other multinationals such as Syngenta, BASF, Bayer and Monsanto are also manifesting themselves on the market of resilience-boosting products. Syngenta is now marketing the biostimulant Hicure and BASF has taken over Becker Underwood, specialised in biological seed treatment. Bayer has submitted an application for the approval of its ‘green’ line of Serenade fungicides and Monsanto is developing various products through its subsidiary BioDirect.
Plant strengtheners
Biobest, established in Lier and a subsidiary of Biobest NV in Belgium, has also developed activities on the market for plant strengthening products. Biobest recently expanded its product range with several items that have a plant-strengthening effect. One of these is Greenstim, about which Biobest claims that it accelerates the transport of specific nutrients. According to this supplier of horticultural products, this has a positive effect on the quality of fruit and perishability. Prestop and PreFeRal are two products that have been introduced into the Biobest range of biological products. Prestop is a biofungicide that combats Botrytis in various crops. Bart Sosef, Director of Biobest Nederland, expects the company’s range of biological products to be expanded in the near future. In relation to this, he has mentioned the fungus Trichoderma, which has a destructive effect on roots.
Biobest is evolving from a manufacturer and supplier of exclusively microbial products into a company that is also active in ‘macrobials’: useful insects and pollinators. Microbials focus more on fungicides that have a direct effect on pests, and in relation to which Sosef has mentioned the biological insecticide PreFeRal. Biobest is seeking collaboration with various partners for the further development of these products, while the marketing emphasis will be placed on guidance and advice. ‘Biobest aims to bring only products to the market that can guarantee the effectiveness they claim,’ explains Sosef.
Text: Tuinbouwteksten.nl/Suzan Crooijmans. Photos: Fotostudio GJ Vlekke, GAPS Photography.
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Plant resilience is becoming the new standard
Resilient crops and robust cultivation systems are in the spotlight these days. We want plants that are tough enough to withstand disease from mere contact with a fungus, virus or bacterium. Researchers and the corporate community have joined forces in the quest for increased crop resilience.
Increasing consumer demand for environmentally-friendly grown and residue-free produce is putting the use of chemical crop protection agents under pressure. At the same time - or in connection with this - an increasing number of crop protection agents are no longer available. The horticulture industry is therefore hard at work searching for alternative ways to protect crops from pests and diseases.
What does resilient mean?
Resilience is a modern name for a natural way of being that has almost been forgotten. For many years, the necessity of crop resilience was relegated to the background with the advent of chemical agents, while the intensification of horticultural crop production was placing a more strenuous burden on crop health at the same time. Cultivation methods, the speed at which crops are produced, the larger number of plants being grown, the greenhouse climate, varietal selection and the use of chemical crop protection agents have all been instrumental in the extent to which plants are resilient and susceptible to disease and damage.
Now that sustainable cultivation has become a market criterion, plant resilience is quickly gaining in importance. Additionally, due to the increasingly narrower package of chemical agents available today, treating your crops with chemical agents no longer as self-evident as it was a few years ago. As a result, plant resilience is becoming an increasingly urgent point on the agenda. At the same time, there is a large group of growers who don’t find the problem to be as pressing: ‘We still have chemistry, don’t we? There must be some adjustments that can be made.’
The number of activities and studies currently focusing on ways to increase plant resilience - and therefore reducing plants’ susceptibility to pests and diseases - is astounding. The numerous studies are being regarded with great interest. They are receiving financial support from governmental institutions and applauded by environmental and social organisations. If we are successful in increasing plant resilience, our faith in healthy cultivation without any need for chemicals will surely increase.
Plant resilience is, however, very difficult to measure. Methods used for this include scouring for symptoms of disease, measuring spore impact or conducting tests for disease on flower and plant materials (bio-testing). A proposal was submitted at the ‘Topsector Tuinbouw en Uitgangsmaterialen’ summit for horticulture and plant materials held in September 2015 for in-depth research into the measurability of plant resistance.
Influence of light and substrate
Parameters are being sought on a diversity of fields to influence plant resilience. A connection has been discovered, for example, between plant resilience and light. Red light, far-red light and UV light all have an effect in the immune system. Studies into plant resilience in relation to light have been conducted at the initiative of Philips and Wageningen University and Research Centre (WUR). One of the conclusions is as follows: ‘We know from literature that light is not necessary for assimilation alone; those parts of a plant that are exposed to sufficient light are less susceptible to mildew, for example.’
Several studies are investigating the effect of substrates on plant resilience. A perfect example is injection with rhizobacteria. This natural enrichment of substrates, called Induced Systematic Resistance (IRS), has been noted as highly promising by the WUR research staff. Additionally, endophytes – micro-organisms – are also being investigated as an alternative for boosting resilience. Another factor to take into consideration involves plant strengtheners, such as seaweed, mineral oil, fatty acids, garlic and fungus spores.
The end of 2014 saw numerous proposals for fundamental research being submitted to the Netherlands Organisation for Scientific Research (NWO Green) within the framework of the ‘Topsector Tuinbouw en Uitgangsmaterialen’ summit. One of the studies given a green light was a project investigating plant resilience in chrysanthemum cultivation. The study focuses on how the inoculation of sterilized soil media with soil micro-organisms affected the sensitivity of above-ground pests. The research objective was to develop soil inoculants that could be used to promote resilience in cut flower varieties against diseases and pests in the soil as well as above the ground.
Soil life
An in-depth research report recently published by a team of WUR researchers, ‘Resilient substrate’, discusses the prospects of resilient cultivation. According to this report, the viability of resilient cultivation is not only confirmed by facts derived from scientific literature, but also by the practical experiences of growers. Increasing plant resilience via the substrate is anticipated to become an increasingly important aspect to take into consideration in combating above-ground pests and diseases. Nutrients in the soil have a direct as well as indirect influence on the resilience of a crop against a diversity of pathogens. The quality and amount of organic substances are key factors in determining the composition of microbial soil life and, as such, crop resilience. Soil life is influenced by organic additives in the form of compost. The type of substrate also plays an important part in this. Coco is rich in bacteria, fungus and protozoans, for example, while rockwool contains mainly bacteria. It is highly probable that not all substrates have the same potential for resilience. Case studies have confirmed this. Cucumber plants grown on champost substrate mats (a residual product from the mushroom sector), for example, are less susceptible to Pythium and mildew. Crops grown on this substrate, which has a hight organic substance content and contains numerous active micro-organisms, will therefore be more resilient.
Researchers have noted that the number of studies demonstrating the impact of the substrate on above-ground pests and diseases is still limited. Apart from that, the effects are not yet conclusive enough to enable this method to serve as an alternative for chemical crop protection. ‘But that’s not what we are aiming for,’ says WUR researcher Jantineke Hofland. ‘We are more inclined to consider this a step towards the full-scale adjustment of the entire cultivation system. Not just one change, but multiple changes at the same time. The entire system needs to be thoroughly reviewed. Now that several studies have shown that plant resilience can be controlled, our research is ready for a next step: the integration of plant resilience into a comprehensive system.’
Two routes
Resilience in plants runs through two different routes: the jasmonic acid route and the salicylic acid route. These routes are named for the alarm substances produced in a plant following a predator attack. Jasmonic acid is produced when plants are exposed to phloem-sap sucking insects and fungi that kill plant tissue and live on dying plant materials, such as Botrytes and Phytophthora. Salicylic acid is formed following an attack by micro-organisms on living plant material. Examples are downy mildew, powdery mildew, rust and scabies
Plant strengtheners are agents that are used preventively and work much in the same way as does a vaccine. Just as pathogens, they stimulate plants to create proteins that increase resistance to disease. Plant strengtheners are not crop protection agents. They increase resistance, but cannot offer a guarantee that plants will not be damaged.
The plant strengtheners used in practice generally focus on boosting resistance via the salicylic route. The Greenhouse Horticulture division of WUR in Bleiswijk is currently researching plant strengtheners. A study conducted on cucumbers tested eight different plant strengtheners, which were administered preventively by spraying them onto the leaves or pouring them onto the roots. The crops were then injected with mildew. Despite the fact that all the plants were, in the end, damaged by the mildew, it took longer for them be infected.
Green crop protection agents
As soon as a product is developed that successfully combats pests or diseases in plants, an application must be submitted for its authorisation. All crop protection agents must be approved by the Board for the Authorisation of Plant Protection Products and Biocides (College voor de Toelating van Gewasbeschermingsmiddelen en Biociden, Ctgb) before they can be marketed. The procedure for ‘green’ crop protection agents is, however, difficult and slow. This is because European regulations for the authorisation of biological crop protection agents have not yet been described. To force an accelerated assessment procedure, the Netherlands has launched the Green Deal ‘Green Crop Protection Agents’ project. Green crop protection agents are substances of a natural origin such as plants micro-organisms and minerals. Plant strengtheners with a nutrient component can be granted authorisation as a fertiliser. The Nutrients Management Institute (Nutriënten Management Instituut, NMI) is the agency that determines this. In practice it makes no difference whether a product has been approved as a fertiliser or a crop protection agent.
Device
In early 2015 a grant application was submitted to the Netherlands Enterprise Agency (Rijksdienst voor Ondernemend Nederland, RVO) for a device that would boost plant resilience in greenhouse horticulture. The device is intended to ‘increase the resilience of greenhouse-grown plants against diseases in a biological manner and in which no chemical substances or metals are applied and the use of crop protection agents is reduced’. The device is ‘a system for increasing plant resilience, excluding water storage facilities and irrigation systems’.
Text: Tuinbouwteksten.nl/Suzan Crooijmans. Photos: Fotostudio GJ Vlekke, GAPS Photography.
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