Frequently Asked Questions

Because no light penetrates into the soil, soil organisms cannot use sunlight for photosynthesis as an energy source and are therefor dependent on organic matter for their energy and food supply.

Organic matter contributes to nutrient delivery, moisture and air management and soil structure.

CO2 is captured in the soil organic material as carbon.

Micro-organisms are also a major source of soil organic material.

Plants capture CO2 from the air through photosynthesis into organic matter; therefore, leaves, wood and roots form an endless storage vessel for CO2.

Soil life (fungi, bacteria, small insects etc.) also breaks down organic material. This causes CO2 to be released again. This is known as the carbon cycle.

Soil organic matter includes all material in the soil derived from microorganisms, plants and animals, mainly made up of carbon, oxygen and hydrogen.

It also contains organic compounds such as proteins and amino acids, which include nitrogen, phosphorus and sulphur.

As a guideline, soil organic carbon makes up about 50% of soil organic matter, though this can range between 30% and 70%.

The actual carbon content depends on factors like the origin of the organic matter and the soil type.

CO₂ is captured in the soil organic material as carbon. Plants capture CO₂ from the air through photosynthesis into organic matter, so leaves, wood and roots form an endless storage vessel for CO₂.

Micro-organisms are a major source of soil organic material, but soil life (fungi, bacteria, insects etc.) also breaks down organic material.This releases CO₂ again, what is known as the carbon cycle.

CO2 capture in organic matter therefore depends on the type of organic matter: stable organic matter contains more carbon than fresh organic matter.

The activity of the soil life is important for the degree of degradation. Carbon Check provides insight into the amount of carbon captured.

At COP21 (Paris) a 4 per 1000 increase was anticipated; an annual increase of 0.4%. On average an increase of 2 ton CO2 can be expected (depending on among others weather conditions and management).

Crops like maize, potatoes and onions take up many nutrients from soil and leave little crop residue. Wheat, barley and grasses form a lot organic matter and contribute to organic matter accumulation.

Provide additional organic matter with animal manure or compost. In the circular economy, the use of compost will become increasingly important.

Keep a growing crop on the field as much as possible. Different green manure and their contribution to organic matter varies. The choice of green manure depends on the land, soil health and climate.

Leave crop residues (roots, stubble etc.) on the land as much as possible after cultivation. This contributes to soil health and the build-up of organic matter and prevents erosion.

Fertilisation tailored to the crop and soil, plus sufficient water, is essential. Soil and crop analyses provide insight to optimise fertilisation and ensure the crop receives the right nutrients.

Organic matter affects biological, chemical and physical soil fertility.

Organic matter provides nitrogen (N), sulphur (S) and other nutrients to crops by being released during the decomposition of organic matter.

Potassium, magnesium, and calcium loosely bind to negatively charged organic molecules, enabling them to hold positive ions like ammonium or potassium via CEC.

Mineralisation is the process by which organic compounds in or on the soil are converted into inorganic (mineral) compounds, this process is done by microorganisms.

Most organic matter is stable, however, organic matter can disappear through decomposition by soil life and it is re-supplemented by the input of manure, compost and crop residues for example.

The difference between supply and degradation determines whether the content is in balance.

If the decomposition is higher than the supply, the organic matter content decreases and vice versa.

In the first year after application a large part of the organic matter disappears because it is easily degradable.

The contribution of this fraction to the content in the soil is quite small. The contribution of the more stable fraction is greater.

Effectively increasing the organic matter content with a green manure crop works best with a crop with a low decomposition rate and a high carbon/nitrogen ratio (C/N ratio).

The content of effective organic matter (EOM) determines how long the positive effects on water retention capacity and soil structure will be noticeable.

Green manure breakdown and EOM contribution are shown by the humification coefficient (HC). At HC 0.7, 70% decomposes in a year, leaving 30% as stable organic matter.

Dynamic organic matter increases chemical soil fertility and is food for bacteria; stable organic matter increases physical soil fertility and is food for soil fungi. Both contribute to soilfertility.

The build-up of organic matter in soil takes time and requires the continuous attention of the farmer/grower. Soil management and mineralisation by soil life have a great effect on carbon capture.

Climatic conditions, temperature and precipitation are also very influential.

Annual monitoring provides insight into the actual state of the soil; measuring and re-measuring the soil carbon status should lead to a significant increase in CO2 storage

When a Soil Carbon Check is performed yearly, improvement can be proved much sooner. Moreover, chain partners in the agri-food sector require up-to-date figures on the condition of the soil.

Only with up-to-date data is it possible to claim and prove sustainable land use.

To establish an increase in SOC of 0.3% (absolute) on arable land, when the initial SOC was 1%, 4 years of sampling (repeated sampling) is needed. Grassland would require 5 years.

Carbon enters soil through decomposing organic matter from root exudates—substances secreted by plant roots and modified by microbes in the rhizosphere.

It is therefore best to sample the soil layer in which most roots are located, or the plough layer (as this is mixed with organic matter). We advise a depth of 30 cm, if possible.

Effective organic matter is the part of the organic matter that remains in the soil one year after application of crop residues, manure or compost.

Green manure crops contribute to the organic matter of the soil. Increasing the organic matter content with a green manure crop works best with a crop with a low decomposition rate and a high C/Nratio

Grasslands are very apt for storing soil organic carbon; permanent grasslands sequester carbon particularly easily.

Arable land is also suitable for storing carbon and although in arable farming systems sequestering carbon can be challenging, there is very high potential.

Soil Carbon Check measures CO₂ stored in soil and tracks capture over time using NIRS-based organic matter analysis, adding depth to Fertilisation Manager’s C-determination.

The report of Soil Carbon Check is supported by the Carbon Calculator. This makes it possible to determine the effect on carbon capture of a crop, green manure crop or animal manure or compost.

The advice that follows makes possible to optimize the carbon management for the own situation.

To express the climate impact, soil carbon capture is converted to CO₂ using a fixed factor based on molecular weight.

A factor of 44/12 = 3.67 (molar mass CO₂/molar mass C) is applied. This means 1 ton of soil carbon equals 3.67 tons of CO₂ captured.

The Carbon Calculator shows how crops, green manure, compost, or animal manure affect carbon capture and gives tailored advice to optimise farm carbon management.

The Carbon Calculator also shows the amount of additional carbon you have stored, in tonnes per hectare, and therefore how many carbon credits you may be able to claim.

Use the link or QR-code on your report to open the Carbon Calculator. With your latest soil carbon data you can optimise your choice of crop or which manure (green/compost) to apply on your fields.