The supply of nutrients to plants in ecological agriculture is based on the turnover of organic matter in soil, as manures, crop residues or native soil organic matter.
Key processes are the mineralization of organic matter.
In a concerted action animals and microorganisms break down complex organic matter to mineral products. In dense soil there will be a physical protection of dead organic material, bacteria and fungi against grazing of fauna, and in wet climates also large risks of anaerobic conditions. These factors lead to retarded mineralization. The reduced nitrogen mineralization in the compacted soil are probably due to increased physical protection of organic material including microbial biomass, against grazing nematodes. The reductions were largest in ley years.