Skip to main content

Practice focus|17 May, 2021

Q&A with Tuomas and Iiris Mattila on the trials and errors of cultivating healthy soil


On Kilpiä Farm, soil is more than a medium for growing crops. It's a living laboratory where an endless series of experiments take place. Luckily, farmers Tuomas and Iiris Mattila—who also happen to be a chemical engineer and microbiologist, respectively—are more than happy to share their findings with other farmers across the Baltic region.

“The way we put it when we’re talking to other farmers is that, ‘We make mistakes so you can make bigger mistakes,’” says Tuomas.

The mistakes appear to be paying off, in any case. In 2018, Tuomas and Iiris received the national Baltic Sea Farmer of the Year Award in recognition of their holistic management style and application of innovative, researched-based methods to curb erosion and its detrimental effects on water bodies. Here, we catch up with them to learn more about what exactly happens on their research and educational farm, and to dig deeper into the topic of soil health.

Q: You call Kilpiä Farm a “research and educational farm.” Why is that?

Tuomas: We test stuff that is emerging internationally and in research. We try to put it into practice and, for the most part, we do it without external funding.

The exception is this Soil Diver agro-research project we’re involved in, where we test what plowing does to soil. We have an actual research plot where we have four strips of moldboard plowed field and four strips of surface cultivated (to 8 cm depth) field. The researchers monitor stuff like earthworms and microbes and greenhouse gas emissions. And I monitor stuff like soil erosion rates and aggregate stability, and compaction and stuff like that like. This is more of the hardcore research side of things. And then we do a lot of experimentation and outreach. We tell other farmers about what we find and arrange field days so they can come and have a look.

Iiris: Researchers sometimes visit during field days too. It’s fun to have field days for farmers and researchers at the same time. The researchers explain stuff they have done and learned, and then the farmers ask the hard questions about putting it all into practice.

Q: So, what exactly is soil, and what makes it "healthy"?

Tuomas: One lightbulb moment for me was realizing that basically, when you grab a clump of soil there actually should not be more than 50% of soil there. The remaining half or more is air and water. So we’re actually farming air and water which is stuck inside a solid matter, and that kind of air and water space is home to all of the soil life.

My definition of healthy soil is that it’s not kaput. It’s not broken…it’s a combination of chemical properties, physical properties, and biological properties. And if any of these are completely out of whack, the soil will suffer. So defining healthy soil is really about going through each plot and asking, “How is this soil doing?”

Q: What role does soil play in the reduction of eutrophication? 

Tuomas:  Water is a yield limiting factor. The better the soil structure, the more water you can store in the soil for later plant use. And the more water you can use through plants, the less run-off you have. So, it’s a case where it’s an absolute win-win, in a sense, for farmers.

Q: Why is it important to for farmers to know their soil?

Tuomas: In Finnish, a farmer is a maanviljelijä which is a soil cultivator in a sense. So, that’s what a farmer does, works with soil in a kind of very drawn out fashion. Really, for a lot of things that we manage as farmers, like sowing and fertilizing and weed control, whether it works or not depends on the condition of the soil. If the soil is in bad shape, you can plant the best crop there is and it’s just going to die, or produce a really poor yield.

Iiris: In order to take care of your land, you have to know your soil. When to go to your field, when it’s dry enough or wet enough, how much fertilizer or organic amendments to use, or what kind of yield to expect is quite different for different soils. You can accidentally degrade your soil by using purchased amendments like fertilizers and pesticides if you don’t know what’s going on.

Tuomas: Yeah, it’s interesting. In one study, researchers gave farmers tools to estimate how much nitrogen would be released from the soil without additional fertilizer, and the farmers were able to use that information to cut their fertilizer rates in half while getting the same yield.  So, that’s a good example of why it’s good to know your soil.

Iiris and Tuomas have planted apple tress on sloping fields

Q: What are some good ways to find out what’s going on in your soil?

Iiris: You can check certain issues, like with the soil sample test results you get the micronutrients and a bit of the macronutrients and the organic matter content. But what you can't see from these tests is if your soil is compacted. And part of a healthy soil is also water infiltration and water retention capacity, which you can see when you dig a hole. Usually, Tuomas goes around the fields digging holes…

Tuomas: Yeah, I dig about 400 holes a year, or something like that… The way I approach it is I start by going through some basic checks. I take a shovel, dig, and see what the plants are doing in the soil. If the plants are growing well, the roots are growing well, and there are signs of earthworms and activity—and no signs of water-logging—then that looks pretty good. But then there’s the soil tests that help you check if there are major deficiencies or excesses of nutrients. And then, does the soil smell nice? Is it crumbly?

One thing is digging holes, and the other thing is just observing, because you always have a natural experiment going on there. You get a large amount of rain, and then you go check on the field, what happens? Is it waterlogged? How long does it take for the water to disappear? After the rainfall, how does it take before the plants start suffering from drought? So the better the system functions, the healthier the soil.

Q: What are some of the soil challenges you’ve had to overcome on your own farm?

Tuomas: We pretty much have silt in our soils, which makes the soil prone to erosion and compaction. If it gets wet, the structure collapses pretty easily—especially if there aren’t plants and a root structure to hold it up.

And then, the land went through the green revolution period in the 60s where the main cultivation was spring cereals, usually followed by no plant cover during the winter, and that damaged the soil structure quite heavily during the decades before we started farming.

So, there was a period of trying to figure out what was going on. We shifted to organic and thought, "OK this will fix it, we will get grasses back growingthere and this will fix it.” But a few years into the organic, we realized: “this is not fixing it.” The grass roots were not growing deeper in the soil because the soil was really compacted. We’ve been fixing things for 12 years now, and most of the stuff is fixed. And we’re hopefully not making any more big mistakes for the next generation to cope with.

Q: What kind of solutions have you implemented?

Tuomas: I think number one was to aim for continuous plant cover. So to have living roots in the soil all the time, which was especially important for these silty soils— to kind of keep them together and improve aggregation. And then, where roots didn’t grow, we subsoiled them. We used a soil loosener which breaks compaction but keeps plants alive so the roots can stabilize it back. And then we retrofitted all the tractors with low pressure tires to reduce compaction to a minimum.

Iiris: We’ve also been trying to diversify the amount of cultivated species. For example putting in many many different kinds of plants to the green manures, like 10 different kinds of plants. 

Tuomas: The more diversity you have above ground, the more potential for diversity you have below ground, because different plants feed different microbes.

Iiris: Another thing to consider is the megastructure design of your agricultural systems. Like in our orchard, the field is so steep that you can’t really drive tractors and harvesters without compacting the soil. Also, shelter belts can protect from erosion caused by high winds.

Tuomas: We’ve basically been doing as ants and bees do: They go around and dig holes. And if they see a problem somewhere, they fiddle with it until the problem is gone. So that’s what we do. We go around the agro-ecosystem and check if there is something wrong, a problem here, and then we start fiddling with that problem until it’s gone.

Like, once we realized how bad water-logging is for soils, and how to check for that…we started fiddling with it...

Q: Can you tell us more about that? What is water-logging and why is it so bad for the soil?

An ideal soil consists of half solid matter and half pores and, ideally, half of those pores will be full of water and the other half will be full of air. When soil gets waterlogged, all the air pores fill with water and there is no oxygen. It results in the pores collapsing, and then the soil gets compacted. So, if there’s too much water there, the water table is too high. A simple test is to dig a few pits and see what happens with the water level. If you get ground water levels up to the top soil, that’s really bad because that means the plants will die, and a lot of the earth worms don’t like it.

For us, it was initially about finding which parts of the drainage system were broken, trying to fix those. In some fields, we ended up redoing the whole drainage system, basically. It cost something like 70,000 Euros to do, or even more. Now, when I dig soil pits, there they are dry, so there's no need to fiddle anymore.

Q: What benefits have you experienced as a result of improving soil health on your farm?

Tuomas: The depth of nice crumbly soil increased from about 5 cm to 35 cm. So that’s the big thing.

Iiris: And erosion has diminished... when we put the windbreaks in, the soil erosion just clearly stopped…And I love the earthworms, we have 5 million per hectare.

Tuomas: The earthworm guy came over and measured for earthworms. He did the first test and said, “Oh there can’t be any more earthworms in Finland…you’ve reached the carrying capacity.”

Q: Have any of the results surprised you?

Tuomas: Well when we started doing subsoiling that was a surprise because … the initial idea was, this might not work and it might kill the grass growth there, but the soil responded really well. And another surprise has been the wind strips and the buffer trees. When you go and dig with a shovel there, like only two years after we planted them, the whole soil was crumbly and like fungi like a forest, only after a few years at least and that was a surprise.

Tuomas and Iiris Mattila won the Baltic Sea Farmer of the Year Award for Finland in 2018

Q: Are there any measures you’ve struggled with?

Tuomas: One big mistake we made happened when we switched to minimum tillage years ago because we realized that plowing is bad for soil life and soil health. It worked on, lets say 90% of the fields, but on 10% it didn’t work at all… It took me eight years to get to the point where I realized, ahh, the drainage is blocked and that’s why the minimum tillage doesn’t work there. So that was kind of humiliating, in a good way. You get these big ideas that you will fix these problems by getting a better cultivator or something, like there’s got to be some technical solution, but then it’s just, oh, there’s a pipe somewhere that’s full of roots, and that’s it. You can’t solve that with a better cultivator. Also, you can’t solve a 75 hectare area with one solution because, well in our case, we have so many different kinds of soil, and so many kinds of different problems.

Q: What are some areas of research related to soil health you think would be interesting to study further?

Iiris: I'm curious about how the communication between plants and their microbiota, the soil microbiology, and the soil biology in general, affects the growth of plants. How the plants respond to the biodiversity of the soil and how the plants and their microbes kind of interact. For example, does having a lot of weeds one year have anything to do with next year’s yield?

Tuomas: I’ve been reading about natural farming in Korea. It was developed decades ago to increase the sales efficiency of Korean agriculture. And one thing they do is they teach farmers to go around their surrounding environment and pick up microbes, cultivate them using local materials—there it’s rice, and here it’s probably oats—and then spread that on the plants to make the plants healthier…Just last week I learned that mosses have a huge variety of microbes and I thought, “Hey maybe next season I’ll do a small trial to see what happens if you extract microbes from moss and spread that on oats.”

The other thing, which might be more scalable, is understanding water better in soils. Now, a lot of farmers have realtime water loggers in their soil. We have one research project where we’ve placed 80 of them all over Finland, it’s called, and now we’re trying to make sense of all that data because it updates every hour. Basically, when you see a rainstorm coming in, you can see what happens with the moisture after that, and it’s a bit different on different fields. So, trying to make sense of what this moisture data is telling us about how soil functions.

Q: What advice do you have for farmers just getting started improving the health of their soil?

Iiris:  I think the first thing would be is to take a shovel and go and see what there is. What kind of soil do you have? Get to know your soil first. Take tests, dig holes. Smell and crumble, and check out what kind of system you already have. Get to know your system and your soil first.

When I was first getting to know my soil and system, it was really helpful to look at the arial maps and photos like you get from satellites on the internet. You can see if part of the field that's not producing is wet. You can correlate these things. It’s really educational.

Tuomas: This soil health thing can be a bit painful for farmers, because farmers have a deep relationship with their fields… It’s important to realize that you’re not in this for a quick fix. You’re in this for developing soil health and learning a lot. I might ask the farmer if they have a friend, another farmer who has similar problems. Because, I’ve realized that farmers who have somebody to talk to and work with on these things learn a lot more and realize that they are not the only ones having problems with soil health…the best combination is when interested farmers form a small learning group, and then have an advisor there. It takes many years of process, but you can see the changes.


Location: Pusula in southern Finland

Type of farm: Organic crop farm (255 ha)

Main production: Rye, oats, green manure and apples

Key practices: Erosion control and soil conditioning, minimum tillage, tillage based on contour lines, conversion of vulnerable fields to orchards, continuous plant coverage, crop rotation, drainage system improvements

Last modified 21/07/22

Close search