Publication Soil research yields useful insights for Flanders and Europe: results from 5 years of EJP SOIL

Healthier soils and climate smart(er) soil management?

Practical insights that farmers can use to make soils more climate-smart: that is one result of the recently completed research program 'EJP SOIL'. Five years of international research also yielded policy-support work for the EU and member states. Greet Ruysschaert, ILVO soil researcher: 'Climate-smart soil management boils down to three efforts: 1) more long-term carbon sequestration, 2) a reduction of soil emissions, and 3) increased soil resilience in the face of climate extremes. This requires a combination of carefully chosen farming approaches.'

EJP SOIL, the European Soil Joint Programme, brought together nearly 1,000 researchers, policy makers and agricultural stakeholders from 24 European countries over 5 years . They built knowledge around themes such as carbon sequestration, water management and soil biodiversity, with a focus on locally applicable solutions.

Specifically for Flanders, the most relevant research results were compiled into a Dutch-language report (see summary below) by ILVO, INBO and the Flemish Department of the Environment. The report was officially presented at the Soil Seminar in January 2025 at ILVO in Merelbeke-Melle.

Lees het eindrapport

EJP SOIL - Summary of 5 years of research on climate-smart management and monitoring of agricultural soils

Report summary:

Stopping soil degradation and boosting soil health

More than 60% of all soils in Europe are affected by one or more forms of soil degradation. In Europe, soil carbon stocks decreased by 0.75% over 10 years (between 2009 and 2018). For agricultural soils, this amounts to CO2 emissions of 25.7 million tons of CO2 per year. (By comparison, the same amount of CO2 is also emitted by burning e.g. 8.7 million m3 of diesel).
In addition to the loss of soil organic matter, many soils are also subject to other forms of degradation such as erosion, compaction or pollution.

The soil condition is in seriously bad shape, according to European JRC (Joint Research Center) scientists and policy makers. In recent years, efforts have therefore been made to improve soil policy and targeted research programs such as EJP SOIL, now succeeded by projects under the Soil Mission, with carbon sequestration as a central ambition. The basic reasoning is as follows: When the carbon stocks of soils increase (again), it is a smart and natural way to sequester CO2. Two forms (or phases) of carbon accumulation in agricultural soils are recognized:

1. Slow down or stop the decline of carbon stocks using beneficial agricultural practices. No COI2 is being removed from the air but at least the loss of carbon from the soil is slowed down.
2. Truly increase the soil carbon stock: This actually takes CO2 out of the air and stores it in the soil.

In both cases, one compares the result of the (recorded) additional agricultural efforts with the carbon stock in the case if the soil or cultivation measures had not happened.

In addition to climate-mitigating, soil organic carbon also acts positively on overall soil quality, erosion susceptibility and water balance.

How can we promote carbon accumulation in agricultural soils?

Building up carbon in soil is a slow and modest process—and it only works if we keep at it. If carbon-friendly practices are abandoned, the stored carbon can quickly be lost again, escaping into the atmosphere as CO₂. Here’s what research is telling us:

Let plants do what they do best: capture carbon

Carbon storage in soil starts with a natural process: photosynthesis. With sunlight as its engine, plants absorb CO₂ from the air and water from the soil, producing oxygen and glucose (sugar). That glucose fuels growth above and below ground. When plant material dies, it falls to the soil, where it’s broken down by microbes—fungi, bacteria, and more—and converted into organic matter. The carbon captured this way is sequestered in the soil and no longer contributes to global warming. Knowing this, we can optimize the photosynthetic potential of crops to maximize carbon accumulation.

• Keep Green in the Field Longer. The longer plants photosynthesize during the year, the more carbon they can transfer into the soil. Crops with a long growing season, such as winter grains or temporary grasslands, are great choices for building soil carbon. After harvesting early-season crops, quickly sow a cover crop mix. The earlier it's planted, the longer it can photosynthesize—and the more biomass and carbon it returns to the soil.

• The Power of Roots? For decades, agricultural research focused on above-ground plant residue. But now we know that carbon from roots—and from the organic compounds they release (exudates)—is two to three times more stable in the soil.
  "That means this carbon stays locked in the soil much longer than above-ground residues," says Adriaan Vanderhasselt, soil researcher at ILVO. "Root components are more resistant to breakdown and bond more tightly with soil aggregates."
• Choosing the Right Crops Some crops direct more CO₂ toward root biomass and root exudates. Deep- and intensively-rooted crops are the better bet if your goal is carbon building.

Crops differ in how much carbon they help store. In the EJP SOIL project, ILVO studied the effect of legumes in crop rotation, using long-term European field trials. Legumes grown for seed (like field beans, soy, or peas) showed no positive impact on soil carbon. But forage legumes harvested for their entire above-ground biomass—like alfalfa, clover, vetch, or clover mixes—did have a significant effect. The more forage legumes in the rotation, the greater the carbon gain. This study did not assess the combined effect of seed legumes followed by a robust cover crop. Of course, many other factors influence smart rotation planning.

• Agroforestry: Integrating trees or shrubs into cropping systems produces more total biomass. These systems capture significantly more long-term carbon—above and below ground—than cropping alone.
• Smart Variety Selection. EJP SOIL revealed significant differences in root development among varieties of the same crop. For winter wheat, for example, an extensive comparative study revealed that some varieties scored high both in yield and in carbon-rich root biomass. Other crops (including all of the varieties) have not yet been examined. Plant breeders note that local factors like soil type and weather may influence root growth and yield more than genetics..

Carbon-Boosting Fertilizers:

Compost

A series of Flemish field trials—including ILVO’s 12-year BOPACT study—shows that stable organic soil amendments like compost contribute significantly to long-term soil carbon storage.

"There’s real potential here," says ILVO researcher Tommy D’Hose. "But we also need to keep an eye on possible side effects, like nutrient runoff."

In the BOPACT trial, compost was added each year on top of standard fertilization with slurry and synthetic fertilizers. This also increased inputs of nitrogen, potassium, and phosphorus. So far, there’s been no observed rise in nitrate leaching, but a slight increase in phosphorus runoff risk.

The addition of carbon-rich soil improvers like compost don’t just add carbon—they enrich soil biology. In five ILVO trials comparing the carbon-rich soil improvers compost, digestate, manure, and biochar improved both topsoil carbon and microbial indicators.

Is Biomass Availability a Limiting Factor?

How feasible is large-scale composting if compostable biomass—like clippings, crop residues, or wood chips—is limited? EJP SOIL explored this concern at the regional level. The answer: the supply of green compost is not endless. Supplying enough for widespread application in arable farming is a challenge.

Thus, it will not be feasible to supply sufficient compost on a large scale for carbon sequestration in agriculture.

Likewise, large-scale use of biochar—a charcoal-like product made by heating biomass in low-oxygen conditions—is not yet practical due to insufficient production capacity.

Likewise, large-scale use of biochar—a charcoal-like product made by heating biomass in low-oxygen conditions—is not yet practical. Though biochar is incredibly stable and effective at locking carbon in soil, current European production is too limited and costly. EJP SOIL estimates it would take 68 years to scale up biomass supplies and production capacity to fully implement biochar across European farmlands.

Cascade Use of Compost and Biochar: a good solution

ILVO proposes a cascading use model to avoid competition for biomass and green compost.

Tension arises between the application of green compost directly to farmland vs. using it horticultural growing media as a peat alternative. Growers value compost for its high microbial biomass, nutrients, and inorganic carbon—making it a good substitute for fertilizers and lime in substrates.

The cascade concept works like this: green-compost-based substrates perform well in greenhouses. After use, those substrates can still be applied to farmland. In fact, their properties improve after crop cultivation. “Post-greenhouse substrates actually make better soil improvers than fresh compost,” says ILVO’s Bart Vandecasteele. “They contain more, and more stable, carbon.”

The Case for Less Tillage

• It’s long been observed that perennial crops (like permanent grasslands) steadily build subsoil carbon, since tillage doesn’t interrupt photosynthesis and decomposition cycles.

  That’s why no-till or reduced tillage is often promoted. It concentrates carbon in the topsoil. But ILVO’s long-term BOPACT data shows a more nuanced picture.

  “No-till systems store more carbon in the top 0–10 cm,” says ILVO’s Tommy D’Hose, “but less in the 10–30 cm range. Plowed soils distribute carbon more evenly through the profile.”

  In Flemish soils, both plowing and non-inversion tillage score similarly for total carbon. So no-till may be better for other ecosystem services: more soil life, less erosion, better water retention.

• Rewetting peatlands was a major theme in EJP SOIL. Drained peat leaks huge amounts of CO₂. Raising the water table can halt peat decomposition—but it requires a different kind of agriculture (e.g., paludiculture). Flanders has relatively little deep peat compared to northern European countries.

Avoid Extra Nitrous Oxide Emissions

N₂O (nitrous oxide) is a potent greenhouse gas—273 times stronger than CO₂. It forms during denitrification, especially when:

• mineral nitrogen is present (from manure or fertilizer),
• oxygen is scarce (due to rainfall or compaction),
• and carbon-rich residues are incorporated into the soil.

We must ensure that the climate gains from carbon-building practices aren't offset by N₂O losses.

“Fortunately,” says ILVO researcher Peter Maenhout, “meta-analyses from EJP SOIL are reassuring. The climate benefits outweigh the trade-offs.”

Studies show compost and biochar generate the least N₂O. ILVO stands behind compost as a climate-friendly soil amendment.

Precision strategies to reduce emissions are in development under the new VLAIO project, LILA. Timing, dosage, and fertilizer type likely play a big role.

EJP SOIL also developed a general tool—the SOMMIT Index—to assess trade-offs for each practice, soil type, and climate. Now the goal is to tailor a version for Flanders, to guide policy and improve climate accounting.

Water Management: Climate-Proofing the Soil

EJP SOIL also explored strategies to make soils more resilient to drought and heavy rain. A metastudy led by ILVO reviewed 45 years of global data. Top recommendations:

• Keep soil covered with living plants year-round, including in the winter. This improves soil structure and water retention.
• Add organic matter. This binds soil particles and improves water movement. Mulching reduces evaporation.
• Be strategic with tillage. Avoid heavy equipment and deep tillage in poor conditions. To ease compaction, occasional deeper tillage can help—but there's no one-size-fits-all advice.

Again, adaptation depends on local context. In Flanders, cover crops are a no-brainer. In Mediterranean regions, they may compete too much for water.

Conclusion: Challenges and Opportunities

• No single practice works everywhere. Soil types, rainfall, and land use vary—and call for local solutions.

• Skilled management is key for carbon sequestration in soil: choosing the right time for tillage and other actions, the right crop and variety in accordance with your plots, a climate-smart fertilization strategy.
• In Flanders, promising strategies like permanent traffic lanes, legume-rich grasslands, and deep-rooted crops remain underused.

The findings from EJP SOIL offer clear guidance for policymakers and advisors. Investing in soil health is critical—not only for climate targets but also for the long-term productivity of Flemish agriculture.

Want to learn more about soil? Explore our online dossiers.

Soil Health

Carbon sequestration

Fertilization and soil improvement with organic fertilizers

Soil erosion