The term soil organic matter is generally used to represent the organic constituents in the soil. They derive from dying materials of plants and animals, which are being transformed by living soil organisms into different decomposition compounds. A fraction of the compounds becomes stabilized and resistant to further changes. Commonly, the term humus is used synonymously with soil organic matter. Soil organic matter increases the nutrient holding capacity of soils, preventing them from becoming unavailable to plants and improves the water holding capacity. Furthermore, it contributes to a well-aggregated soil structure which allows for a good water infiltration, preventing erosion.

To assess different crop production practices regarding their impacts on the soil organic matter content the following assessment parameters were taken into account:

1. crop type, as plant root and surface residues differ greatly as a source of organic matter: while some crops (e.g. cereals) increase soil organic matter content, others (e.g. sugar beets) effectuate a decrease,
2. addition of organic materials such as solid and liquid manure, or compost,
3. undersown crops and cover crops, because this practices will increase the amount of roots and residue added to the soil and
4. tillage system: reduced tillage tends to conserve or increase soil organic matter, while intensive tillage increases the loss of organic matter by speeding up decomposition of organic materials.

All alternative production practices of all crops defined for the model were assessed by their goal achievement levels using a fuzzy logic tool with the optimum being a medium contribution to soil organic matter content.