compost
“Knowledge of soil organisms is key in ideal potting mixture”
Bark, the main ingredient of orchid substrates, is steamed at high temperatures. This kills off all the impurities and pathogens. But unfortunately it also spells the end of a lot of good things. What remains is a sterile medium – and try growing a resilient crop in that. After all, a healthy plant starts with a healthy root package. So VG Orchids does the logical thing: it has soil organisms added to its substrate.
Adding additives to substrate restores the natural symbioses and creates a healthy environment for the roots. This brings Phalaenopsis growers one step closer to the ideal potting compost.
Over the years, family business VG Orchids, which has two branches in the Dutch town of De Lier and includes the innovative brand VG Colours, has grown from 2,000 m2 of cut Phalaenopsis to 12 hectares of pot orchids. The plants are supplied in 6 and 12 cm pots. Cultivation manager Otwin van Geest has been working exclusively with the new Infigo substrate from BVB Substrates at their main branch for a year now. In addition to bark and pH buffering peat, this mixture contains several additives to ensure stable soil life and good resilience. An important part of this is the microorganism Trichoderma harzianum T-22 (Trianum) from Koppert’s NatuGro package.
Reducing chemicals
A good substrate forms the basis for healthy roots and a resilient plant. But the way in which this knowledge is used varies from grower to grower. For VG Orchids, the choices they make in this area are key to successful and sustainable Phalaenopsis cultivation.
The company therefore follows developments closely, working with their substrate supplier as a regular partner. They too are constantly pushing the boundaries: innovation is a vision both companies share. Van Geest: “We want to progress, and as long as we can see improvements happening, we’re happy to sit down with the customer and come up with solutions. Our ultimate goal is not the mixture per se but rather to reduce our use of chemicals. Crop protection products often stunt plant growth. Besides, as a grower you want to cut down on the amount of chemicals you use. So we are looking for other ways to keep the crop healthy. A resilient plant can solve a lot of problems itself, so we’re fully behind this development.”
Natural resilience
The cultivation manager likes to make the comparison with people. “If a person is regularly exposed to good and bad bacteria in their immediate living environment, they develop a healthy immune system. Then, if they are exposed to increased levels of a pathogen, they will be less likely to fall ill than someone growing up in a sterile environment. And so it is with plants too.”
That is why the environment around the roots is so important, he believes. “There must be enough oxygen and soil organisms in the pot to ensure optimum uptake of important elements and nutrients. And when you can no longer be certain that that is the case – if the substrate is sterile – you have to add those components artificially. In our current mixture, for example, the peat helps the organic elements bind together well and Trianum protects the roots against harmful fungi.”
Thoroughly trialled
The search for the ideal potting compost is a continuous process in which new information and knowledge is constantly being incorporated into solutions. VG Orchids facilitates a think tank that meets regularly to exchange experiences. It is attended by the cultivation manager, a specialist from Aqua Terra Nova, a microbiologist and cultivation specialist from BVB Substrates, a specialist from Koppert and adviser Peter Klapwijk.
“Following these meetings, which we hold once every ten weeks, we usually set up five substrate trials here,” says Van Geest. “Important aspects we test are the proportions of bark, coir, sphagnum and peat, with and without various additives. Previous cultivation trials have shown that the Infigo mixture is best for our company in terms of crop steering. As a result of the research conducted by the think tank, further improvements have been made to this mixture in the form of plant strengthening additives. The results are positive. The pots are full of healthy roots and leaf surface has increased by 20 to 25 percent.”
Continuous measurement and refinement
This collaboration is also worth its weight in gold to the substrate supplier. Orchid specialist Robin Camphens: “We are an innovative company and we want to stay ahead. With this in mind, we recently hired a microbiologist. His expertise is very enlightening and gives a real boost to our work developing new potting compost mixtures. You only need to look at VG Orchids, where he advised on the successful additives for the substrate. Soon, when our new research centre with phytotrons comes into operation, we will be able to focus even more specifically on orchid solutions.”
Camphens’s colleague Richard Bremmer regularly visits the orchid company to monitor the trials. He also checks the performance of the “standard” substrate, of course, and takes soil samples for a complete chemical analysis once every six weeks. The peat in the mixture makes this research possible. Koppert also carries out plant sap, Trianum and soil nutrient web analyses. Once a week, the grower monitors growth in plant height and width and measures the pH and EC. The results are discussed, following which any necessary adjustments are made to the growing formula or new trials are set up. In short, it’s a continuous process of measurement and refinement.
Successful teamwork
The two partners hope to be able to observe more effects of the new substrate in the near future. Bremmer: “We expect a more resilient crop to lead to fewer losses. And of course the quality should be better too: a healthy plant branches better and produces lots of buds. I am gradually seeing an upward trend. Of course, resilience depends on several factors. Your crop protection strategy must be right, you must get your hygiene right – that sort of thing. But the main focus is still on the root environment, and our grower-specific potting compost mixture is an important step in this direction.”
Van Geest appreciates the supplier’s input. “Their knowledge is pure added value for us. We have every faith in their people and their product. The quality is consistent year round, and orchids appreciate that; inconsistency leads to stress and stunted growth. And as a grower, that’s something you want to prevent at all costs. A resilient plant can do so much more.”
Summary
The Dutch pot plant company VG Orchids has switched to a tailor-made substrate for Phalaenopsis. Standard potting composts are often too sterile and VG Orchids hopes to create a healthier climate for the roots with additives like peat and Trianum. A good mixture is the basis for a strong root package and, ultimately, a more resilient crop. This resilience should reduce stress and offers growers an opportunity to reduce their use of chemicals.
Text: Jojanneke Rodenburg.
Images: Studio G.J. Vlekke.
Related
Coco peat and biochar are good alternatives for peat in potting soil
Most potting soils contain a large amount of peat. But clearly a turning point has been reached. More and more often growers, customers and consumers are asking for peat-free mixtures. The reasons are the large amount of CO2 that is released during the excavation of peat and the loss of ancient wetlands. This was one of the reasons to start searching for new raw materials for potting soils. A lot of experience has already been gained with coco peat, and biochar, which appears to offer added value, has the potential to become a key ingredient.
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Use compost to increase resistance to plant diseases
In biological cultivation every opportunity to control soil-borne diseases is a bonus. The idea of providing compost components that can make the soil more resistant to pests and diseases is therefore logical. But its implementation is difficult. The material is complex.
Verticillium, root knot nematodes, Fusarium and Pyrenochaeta (corky root rot) cause problems during the organic cultivation of fruit vegetables, while Pythium and Sclerotinia cause problems in leafy crops. In 2014 Wageningen UR Greenhouse Horticulture, of Bleiswijk, the Netherlands, and knowledge institute, Louis Bolk Institute (LBI) together with Bionext and a number of growers therefore started to search for good composts and the possibility of making plants resilient to these pathogens by using compost.
A lot of information on the subject is already available but it mostly relates to experience in practise. There is no clear framework. In addition, compost is a heterogeneous product because it is made from different starting materials and there are different ways of composting.
Develop methodologies
2014 was mostly a year for stocktaking and design of methodologies. You need be able to measure the resilience of the soil and plant before you start the research. Tools were also developed to measure the resistance to nematodes. For this it is important to determine the pore volume of the ground, activity of the microbes, salts and calcium.
Incidentally it is difficult to point to one single mechanism that is directly responsible for the resistance. However, pore volume does affect drainage, distribution of moisture, oxygen permeability and the type of microorganisms present and thereby the degradation of organic matter. Fortunately not all the mechanisms need to be clear so long as the measurements give a good prediction of the resilience. Wageningen UR Greenhouse Horticulture has developed a model that incorporates this knowledge and can give advice about how to stimulate the soil resilience.
Researcher André van der Wurff: “Also, more and more we use measurements based on the DNA of plants. Eventually it is all about the plant, yield and the taste. On the basis of the DNA we can see when a plant is feeling well, and when the preventative defence mechanism is switched on. Substances in the root environment can make plants turn on or off certain genes, so that they may or may not get sick. The ability to predict this is important. Growers are looking for a safe and sure growing concept.”
Handbook compost
Willemien Cuijpers and Leen Janmaat, of LBI, both focus on good ways of composting. Together with Van der Wurff and a large number of overseas colleagues they are working on a manual for growers and compost suppliers about how to deal with compost: For example, what do they need to pay attention to; what should the compost look like, smell and feel and when does it offer resistance?
“Compost is a result of manually controlled degradation and rebuilding process. In this way you build up stable humus,” explains Janmaat. “And humus is the slow biodegradable part of organic material in the soil.”
Compost gives structure to all soil types and plays an important role in resilience. It gives light sandy soil ‘body’, while heavy clay soil becomes lighter. It ensures that plants can take up minerals and it contains microorganisms that compete in order to suppress soil diseases.
Many materials are suitable for composting. On a biological tomato nursery these, for example, could be old crop remains and waste from pruning, combined with clover and lucerne grown on their own land. Therefore the way in which a compost develops is very dependent on the raw materials, the carbon:nitrogen ratio and the moisture level. It’s logical that the soil life in the compost behaves in different ways.
Resistance through competition
It is already known that certain elements in a compost can make a plant more resilient. The soil is crawling with organisms that work together or compete with each other. It is a matter of building up general resistance through competition. Microorganisms fight against each other. In the case of Pythium this happens by competing for food. Other microorganisms are antagonistic and work more specifically. In the case of Verticillium it’s known that non-pathogenic types exist that protect the root against the disease-causing types, Verticillium dahlae. Also Trichoderma protects roots against invaders. Administering these fungi is often carried out during the propagation phase or during planting. A few compost companies add Trichoderma during the final phase of the composting process.
Add nutrients
If you can add nutrient to compost or soil that stimulate the useful bacteria then you can further increase the resilience of the soil. In theory the root knot nematode is a nuisance you can control in such a way.
Earlier research by Van der Wurff showed that a group of bacteria played an important role in resistance to nematodes because they eat chitin. The cell wall of a nematode contains this substance. Therefore if you add this substance to the soil the population of bacteria will increase with the chance that the root know nematode will not be able to develop any further. If this process is to succeed then the acidity has to be right. Chitin is found in the remains of prawns. Also mushroom compost, a by-product of mushroom production, contains a lot of chitin. A potting trial yielded good results.
This year commercial trials are being carried out by BioVerbeek using various compost compositions but it is not yet possible to draw any clear conclusions.
Also for conventional growing
The project is being carried out in biological production but of course it also has an impact on conventional soil grown crops. Here it is still possible to use chemical soil disinfection or steaming. However, these sort of rigorous measures disturb the biological balance of the soil.
If it becomes possible to introduce certain antagonistics or microorganisms into the soil via composts the necessity to fumigate the soil will decrease. The goal is to eventually develop a robust and resilient cultivation system for all crops, biological or conventional.
Summary
All signs indicate that it is possible to use compost to increase resistance to plant diseases. The addition of compost is already an important step towards improving the structure of the soil. A collaboration between two research institutes and entrepreneurs is focused on stimulating native antagonistics that can be added to composts and tested in practise.
Text: Pieternel van Velden. Photos: Louis Bolk Institute