Interview with a Master Agronomist – Stephan Timmermans Shares

I have recently decided to revive the interview format that proved so popular in my first book, Nutrition Rules!. I meet many passionate and gifted souls in my global travels, and these personal discussions can provide a wonderfully intimate platform from which to share. At some point soon, I will extend this sharing to a series of podcast interviews but, for now, we will stick with the written word.

It is appropriate that the first of this series involves a dear friend, the accomplished, biological agronomist from Holland, Stephan Timmermans. Stephan attended my very first seminar in the Netherlands, some 16 years ago, and the message immediately resonated. I have since walked fields and checked crops with him at impassioned pace, lingered behind him during his long distance runs and reunited in various countries over the years, during my European seminar tours.

Our most recent reunion was at my recent two-day event in the UK. Stephan had been sent to the course by a large, Scottish berry producer, for whom he consults two days each fortnight. The following interview was captured over breakfast in the elegant drawing room of a mansion/conference centre, where the seminar was held.

Graeme: It is so nice to be able to share some time with you. It has been many years since we became friends. During visits to your clients’ farms, I was immediately taken with their obvious appreciation of your knowledge, passion and purpose. They were well aware of how lucky they were to have your stewardship. Do you still work with those original growers, as your reputation has grown and the associated demand for your services has increased?

Stephan: My growers have become like a family. I care so much for their enterprises and their success. I still have all of my originals. Even if I wanted to get rid of some of them to allow me to service new clients, they would not allow it. We are together, till death do us part! (laughs)

Graeme: I think you could count on one hand, the agronomists around the world with 100% client retention after so many years. I understand you have expanded out into other countries these days. Where are you working?

Stephan: I work in Belgium, Germany and England, but a few years ago I also began working with a large, berry producer in Scotland. It started with one day, every two weeks, but as the enterprise has grown, I am now needed for two days each fortnight.

Graeme: It sounds like your help has been of value to them, if they are expanding like that. What changes have you witnessed?

Stephan: Well, to be honest, it was a real mess when I started. They grow strawberries, and production was low, quality was bad, and the problems were many. The starting point was to reduce nitrogen. We have gradually reduced N inputs by over 40%.

Graeme: Misuse of nitrogen is such a big story around the world. It is a hugely important mineral, but when we overdo it, there is a price to pay. The starting point is the antagonism of potassium and calcium uptake. You have then created your own nightmare, as these two induced deficiencies are major players in flavour, resilience and production. Have you been using a nitrate meter to determine ideal levels to shoot for during the season?

Stephan: It might be interesting for your readers to know that the best early investment we made for this farm was a spade. No one was ever looking at roots. Please understand that if your agronomist does not have soil under their fingernails at the end of each day, they are not a real agronomist and should be moved on immediately. If you are not checking the roots, smelling the soil and monitoring the biology, all of which requires a spade and common sense, you are driving blind.

Graeme: I couldn’t agree more. Tell me what you look for with that essential tool, the spade, when working with Scottish strawberries.

Stephan: Well, we check every single field with that spade over the two days. We dig around the roots and note the structure of the soil. How easily does the spade penetrate, are there aggregates present? Then, we smell every root zone sample. If there is a lack of that healthy soil smell, we start to worry. Something is wrong with our program. If the biology is struggling through our mismanagement, the whole system struggles.

Graeme: I think the readers might be interested in what we discussed yesterday. You mentioned that there is a swede rotation at these farms. They use glyphosate for that particular crop and, when you get the field back for the berries, the nice, healthy earth smell has disappeared.

Stephan: That’s correct. The soils are returned to me with no smell at all. We make up the beds and begin rebuilding the biology.

Graeme: Can you share some of your more successful soil-life strategies?

Stephan: Certainly. We try to prepare the beds in Autumn, so they can percolate through the winter. The first step is the addition of basaltic rock dust. This gives us the desirable silica base that can be so productive. Then we bring in humates with boron. I find that this combination helps to release the silica in a plant available form, ready for the Spring action.

Graeme: The understanding of boron firing silica solubility is one of the great gifts of Hugh Lovell. He argues that calcium is required for cell division and cell strength in spring, but it is such an absurdly immobile mineral. Phloem and xylem are the nutrient transport highways through which minerals are moved into and around the plant. Hugh stresses that sluggish calcium can move more easily into the plant when we deliver the boron/silica trigger. I have tested this theory and there is no doubt about the validity. Hugh is a brilliant consultant and a lovely man.

Stephan: Yes, I couldn't agree more. I have heard both Hugh and you describe this process. I have worked with this principle for years and it most definitely works. This past year the farmer has begun to brew his own inoculums to fast-track the rebuilding of the biology. At this point we find it takes at least six months before the nice smell returns. It takes that much time to break down the glyphosate, to allow the biology to return.

Graeme: It is really quite a tragedy that this herbicide is amongst the most widely used of all farm chemicals. It is so destructive, and yet we have been sold the lie that it is harmless. Many growers have now become so completely dependent. They genuinely believe that they could not exist without it. Is there any chance you can convince them to drop the glyphosate in the swede rotation?

Stephan: It is a bit of a process but I have recently requested that I receive the fields a year earlier so that we can grow cover crops and really hit the ground running with a vital, living soil for the strawberries. The last thing, when checking each bed, is to look for other evidence of the soil life at work. If they are active, there are these wonderful soil aggregates around the roots and there should also be a nice fuzz on the roots indicating that the Actinomycetes are happy.

Graeme: Actinomycetes are seen as signpost creatures. If they are happy and thriving, then the rest of the soil foodweb is usually flourishing. Is there anything else you look for in this regular root zone inspection?

Stephan: Yes. The other simple, but important test provides an indication of boron status. We stretch the roots. If they stretch like a rubber band, then boron is where it needs to be in that crop. If they break easily when stretching, you are boron deficient, and that shortage needs to be addressed as soon as possible.

Graeme: That’s a great tip for all growers. I guess if you were inspecting a legume crop you would also be checking for nodulation?

Stephan: Most certainly, and we would also be pinching those nodules in half and checking if they have that nice, pinky colour inside.

Graeme: Just returning to the all-important nitrogen story. Have you been using a nitrate meter to determine the sweet spot for strawberries in that region?

Stephan: Yes we have and the crops were between 2500 ppm and 3000 ppm when I started working with them.

Graeme: Wow! That’s much too high for strawberries. What did you do?

Stephan: We had to change nitrogen nutrition if we wanted a healthy, resistant plant. Following your advice, we started using small amounts of urea with humic acid. We also supplemented with amino acids as a foliar. If we use calcium nitrate or ammonium sulphate, it is always in small doses, like 12 kg per hectare. Every nitrogen application will go in with a carbon source, either humic of fulvic acid, depending on compatibility. Strawberries absolutely respond to small amounts, often. They hate applications of 50 or 60 kg at one time.

Graeme: Are you using the nitrogen meter to monitor when you need your small, regular doses of N?

Stephan: Actually, we find that a plant sap EC meter is the best tool for this purpose. We aim for a plant sap EC of 3 to 4 mS/cm in the young plant. If the sap EC rises to 7 or 8 in those early stages. then we are set for a host of problems. The nitrogen starts blocking everything. However, when we get to flowering and picking, we like to increase sap conductivity to around 5 to 6. This helps maintain good vigour and fruit quality.

Graeme: I guess the higher EC after flowering is more likely to be based more on potassium than nitrogen, after flowering. Potassium is the mineral with most impact on plant sap EC. Is this monitoring strategy unique to strawberries or have you found it relevant to other field crops?

Stephan: It took us a year to figure what levels worked best in strawberries. There may be small variations in other crops, but the core concept appears relevant to everything.

Graeme: Just returning to the Nitrate meter. You mentioned that levels were at 3000 ppm when you started working with these guys. What level do you aim for now?

Stephan: We consider we have overdone N, if levels rise above 500 ppm in the sap.

Graeme: Wow! That is lower than I thought. However, I am seeing this everywhere. If you can get those nitrate levels down without impacting vigour, it is usually a great story, for a productive, problem-free crop.

Stephan: We actually find it best to keep nitrate nitrogen down to around 150 ppm to 200 ppm. Remember, I am talking about nitrate nitrogen rather than total nitrogen. We are foliar spraying urea with humic, and amino acids regularly to ensure sufficient N. These are not in the nitrate form, and are much more plant friendly.

Graeme: Do you use the urea with humic acid (urea humates) throughout the season or just during the vegetative stage?

Stephan: We use it most in the early stages. After flowering, we only use it if there is a loss of vigour.

Graeme: Does your guideline of no more than 200 ppm of Nitrate N also apply after flowering?

Stephan: We try to go even lower then. We monitor the sap from the top fully developed leaf and an active bottom leaf, with the meter, and if the lower levels are a little higher that means there is a bit of a bank account. When the bottom leaves begin to display lower levels than the top leaves, it means we have gone into overdraft.

Graeme: So you are using the top leaf/bottom leaf comparison for nitrates, just as we do for potassium, with a potassium meter?

Stephan: Yes, we find it a good guideline. It is not as effective as monitoring potassium because we have determined exactly where we need to be with that mineral, relative to the top leaf and bottom leaf comparison.

Graeme: We find this potassium monitoring technique to be of tremendous value for fingertip control of what I call “the money mineral”. As soon as the lower leaf drops below the top leaf the plant is running low on K and it is time to act.

Stephan: We have done a great deal of work on this and found that, ideally, you need to maintain higher levels of K in the lower leaves, as that ensures a bank account. We try to always maintain the levels in the lower leaves at 500 ppm higher than the top leaves. It has taken a while to figure out this level of precision, but the extra reserve in the lower leaves effectively serves as an insurance policy. During full production, you can suck out potassium overnight, so maintaining this reserve ensures that you don’t have small berries or poor flavour.

Graeme: I have observed the potassium plunge as soon as fruiting kicks in. This is a good insurance policy. Thanks for sharing. What K levels do you aim for usually?

Stephan: In a young strawberry crop, in the vegetative stage before flowering, we aim for 1000 ppm to 1500 ppm, on the Horiba potassium meter. As you move into flowering, that increases to 1500 ppm up to 2000 ppm. In the old leaves, we want to see 2000 ppm up to a maximum of 2500 ppm, at this stage. During the long harvesting stage there is a rule of thumb that the lower leaves must be maintained above 2000 ppm all the time, or you will pay the price. That way there is always a reserve to counter the rapid potassium drawdown that often happens during full fruit production.

Graeme: If you do not have a potassium meter, you are destined to suffer the consequences of the post flowering potassium plummet because you are driving blind.

Stephan: During the first season with the berries we saw potassium levels remaining quite stable during the vegetative stage but within two days of that first flower, the meter would register sudden drops of 1000 ppm. The benefits of monitoring potassium go beyond identifying shortages. Sometime it can be the opposite. In the Netherlands, on the sandy soils, during warm conditions, the mineralisation is really pumping and potassium becomes way too high. Then, this excess antagonises calcium, silica and magnesium and problems begin.

Graeme: How do you fix this problem?

Stephan: We begin with a foliar spray of urea and humic acid to ensure chlorophyll density, and then my favorite solution involves three of your products. We combine Dia-Life™, Gyp-Life™ and Mag-Life™ together, and there is a tremendous response. The potassium is pushed aside with the calcium and magnesium and the good availability of these micronised suspensions ensure rapid uptake of magnesium, silica, calcium and sulfur. This quartet builds root systems wonderfully, and the silica builds the phloem and xylem transport systems within the plant. These suspensions have a low EC so there is never a problem with salts in the plant. Everything works better from thereon in. Silica is the key focus for healthy, resistant strawberries.

Graeme: For those readers not familiar with this product, Dia-Life™ involves micronised diatomaceous earth. Tiny creatures, called diatoms, originally inhabited ponds and lakes in their trillions. Geological upheavals saw their entombment, and all that remains, millions of years later, is their outer skeletons, that consist of 85% silica. This material, that looks a little like limestone, can be crushed down to just 5 microns, held in liquid suspension, and applied to the soil via fertigation. Silica levels in the leaf begin rising immediately. Silica confers cell strength, stem strength and better nutrient transfer, into and around the plant. However, silica is also an immune elicitor and it is here where we see the biggest benefits. Diseased or insect stressed plants invariably have lower silica levels than healthy abundant crops. The exciting thing is that anything that boosts immunity always reduces problems, but also increases yield. It is like a fertiliser response.

Stephan: Let me tell you now. You have developed some wonderful products that I have worked with for years, but my favorite is Dia-Life™. It is absolutely the best!

Graeme: Thanks mate. It is actually one of my favourite products on my farms. The silica is delivered better into the plant with fertigation, but it has other benefits as a foliar spray. We use it in summer, just like kaolin, to help protect vegetables (like capsicums and tomatoes) and fruit from sunburn. It can be a huge issue in our 35 degree temperatures. Diatomaceous earth also has an impact on problem insects. The tiny particles look like broken razor blades under a microscope, and are super abrasive. What kind of application rates of these liquid, micronised minerals do you use per acre?

Stephan: If the crop really needs some help, we will use 5 litres per acre of each of these products. If the need is not so dire, we favour 3 litres of each, per acre. We put them through early in the morning so the lines are flushed during the rest of the day and there is no risk of ever blocking the T-tape.

Graeme: Do you ever add some biology with this mix?

Stephan: Yes. We are increasingly realising the benefits of combining minerals and microbes. I am a fan of your beneficial Bacillus blend, called Micro-Force™. Unfortunately, it is not available in Holland but I can source it when working in the UK. We put the brewed Micro-Force™ through first, and then the three micronised mineral liquids, and then we flush the system. The microbes can take it to another level. This strategy changes the root zone. Aggregates appear almost immediately and a dense fuzz develops on the roots. This big clump of root hairs is the perfect house for the soil life. Then you get this beautiful, sweet smell coming from the soil and you know all is well.

Graeme: Let’s look at some of your mineral strategies now. How do you best manage boron?

Stephan: Sadly, in Holland, we are on sandy soils with low organic matter, so it is very difficult to retain boron for the full season. The best game plan is to spoon-feed boron all through the season. It must always be combined with humic acid, as it is otherwise so easily leached.

Graeme: Do you have favoured application times for boron? I am always insistent that the majority of crops will benefit from a foliar spray or boron, immediately before flowering, as it is such a big player in pollination and fruit set.

Stephan: We do the same, and we always combine humic acid with that foliar. It stabilises the boron and it also buffers what can otherwise be a little harsh.

Graeme: Tell me about your approach to calcium nutrition? Do you see a relevance in the fuzzy line on the refractometer? Do you find a sharp line relates to calcium deficiency?

Stephan: For sure! The refractometer is definitely a reliable calcium meter. If we need calcium and a little growth, we will use calcium nitrate but always in low doses – 12 kg per hectare is the maximum. We will never bomb the plant with large doses and we always combine fulvic acid with the calcium nitrate to create a chelated calcium fulvate.

Graeme: We work a lot with strawberries around the world and they are notoriously calcium hungry. What other ways do you help maintain good calcium in the plant?

Stephan: You are right about their calcium cravings. In our soils we find that we can fertigate a little ammonium sulfate and the acidity can make some of the soil calcium more available. If we are really struggling to keep up with the calcium demands of this plant, then we will apply milk. We use about 15 litres first thing in the morning through the drip and then flush out any residues. Sometimes we may also do a foliar application of milk. The foliar is always done in the evening because you do not want UV on the milk. We use from 10 to 15 litres per hectare with a minimum of four litres. You will see a wonderful shine on the leaves the next morning.

Graeme: Do you notice any fungicidal response with the milk? It is well researched to help manage powdery mildew, but this disease is not normally a big issue in strawberries.

Stephan: We don’t see a direct fungicidal response but there is no doubt that the crop loves the milk and that plant health is improved.

Graeme: Part of the story of hybridisation involves shuffling a finite number of genes to derive a specific outcome, which is usually about ongoing earnings for the plant breeder. The problem is that we can’t make new genes. We redirect some of the genes to do something new and whatever they were previously doing is then neglected. The most common problem relative to this issue is compromised uptake of some minerals. In the case of many of the new strawberry hybrids, they really struggle to uptake manganese. How do you counter this? How do you manage manganese?

Stephan: Manganese can definitely be an issue but there is another factor involved here. We always check the history of a new field, because if glyphosate has been involved, we can expect problems with both manganese and iron. Zinc can also be a problem. We like to foliar spray with your product, Shuttle Seven™, because it has high levels of all the traces. If we need a further boost we will add 1 kg of manganese sulfate, 500 grams of iron sulfate and 250 grams of zinc sulfate to the spray tank with a little fulvic acid to chelate them. We might come back two or three times with this mix.

Graeme: Sounds like a good plan. I like your strategy of little amounts often. How do you look after phosphorus? In intensive horticulture it is usually about managing excess phosphate, but there is still the challenge of keeping phosphate cycling, as it locks up so readily. What is your favorite strategy in this regard?

Stephan: I like to use cover crops to release locked-up phosphorus. Legumes release acids that help break the bond between calcium and phosphorus, but buckwheat is also very helpful. In fact, it can be as effective as legumes for phosphate release.

Graeme: I am seeing an increased use of interplanting around the globe. This is where there can be diverse benefits by combining crops. Peas and canola are a good example. I guess this is not applicable with strawberries, but you work with other crops. Have you had any experience you can share?

Stephan: The biggest concern for Dutch growers is their belief that cover crops can create problems with nematodes. I have found that this only ever happens when the cover crop has been pumped up with nitrogen. It is the nitrates that call in the nematodes. I have seen it time and time again. I do think that intercropping could be viable for strawberries. I work with asparagus and I have seen great results when my growers have planted low growing clovers after harvest. The asparagus is perennial, obviously, but it makes a great difference to the subsequent crop.

Graeme: I describe Nutrition Farming as a “functional hybrid”. You can pull in and dovetail any concepts from anywhere, as long as they work together. There are no rules apart from my one central condition. I ask the question, Does Nature approve?”. In this context, I would like you to share your views on biodynamics. The purists have turned Steiner’s suggestions into a religion, to the point that the great man is probably rolling in his grave. I know you have studied these ideas. Do you see a role for specific biodynamic principle in regenerative agriculture?

Stephan: I have experimented with Biodynamic concepts. One theory that I find of value is the concept of certain days that are better suited to others when seeking specific responses. If you are seeking more foliage for example, then you spray something like urea and humic acid on what is called “a leaf day”. I assure you that you will see a better vegetative response. If you want to initiate a good flowering, then you apply relevant nutrients on a “flower day”. Foliars always work best for these responses but I have found that fertigating Dia-Life™ (silica) on a “root day” will really get some silica up into that plant from the roots. Potatoes and carrots respond wonderfully to feeding and planting on a root day. I have seen potatoes, planted on a leaf day, where the above ground plant is 1.5 metres high, but there are very few tubers.

Graeme: I understand that this concept has been developed by Maria Thun. In her original research, she planted radish seeds every day and noticed the marked difference. Sometimes they went to seed without bulbing up, other times they fattened out beautifully and sometimes they elongated. Maria Thun also developed the Cosmic Calendar, which can be used as a guideline for weather forecasting many weeks ahead.

Stephan: It took quite some effort to understand exactly how this works, but now I find it to be of real value. You would be surprised at the number of conventional growers who call me for long range forecasts based on Maria’s concepts.

Graeme: I have to get on stage shortly, so this will be my last question. What, in your experience, is the most powerful example of the profound link between nutrition and pest pressure?

Stephan: There is no doubt about it. The mismanagement of nitrogen is the biggest player. If you want pests and disease, just start pouring on the nitrogen. Growers put too much importance on this mineral. My most successful growers focus upon having their nitrogen as low as possible. You don’t ever want to undersupply nitrogen, but so many times it is overdone. In the biochemical sequence, it is silica first, then calcium, then magnesium. Nitrogen is fourth. Just watch what happens if you focus on that mix I mentioned with Dia-Life™, Gyp-Life™ and Mag-Life™. This blend focuses on the first three minerals in the biochemical sequence and it works a treat.

Graeme: Thanks for your selfless sharing. I am sure that many of my growers will be appreciative of your wisdom.

Stephan: It has been a pleasure.