Abstract: In temperate climates, increased soil fertility is strictly related to the accumulation of humified organic matter, with the creation of vegetal soil as the primary means of expanding biomass production per unit area. In the wild, Nature accomplishes this process efficiently, but in cultivated fields, humification is relatively neglected, which leads to impoverished soil quality. The reason for this is that the accumulation of residues from any single crop disrupts the humification process, which induces modified decomposition that delays the stabilisation and increases the release of toxic metabolites. These toxins, in turn, can induce specific allelopathic effects (dispathy) that can result in ‘soil sickness’ under repeated cultivation conditions. Root absorption, in particular, can become hindered by toxins from previous crop residues, which promotes dystrophies and root die-back. Thus, the sustainability of an agricultural system can be significantly improved through better control of the evolution of the soil organic matter through mimicking of the natural process of humification. To become truly effective, this process has the need for biodiversity, such as crop rotation or intercropping, use of organic amendments, and/or reduction in pesticide, fertiliser and tillage practices. The restoration of humification within soils also enhances the natural suppression of soil-borne diseases, plus induction of stronger and healthier plants that are less vulnerable to pathogens and parasites; furthermore, this also diminishes the needs for pesticide sprays.