The integration of organic fertilisers into agricultural practices is one approach to enable more efficient agricultural management systems to decrease adverse environmental impacts of agriculture. In this context, the objective of this research was to determine the impact of long-term crop rotation and organic and mineral fertilisation on soil humus content, humic and fulvic acids, organic matter humification in organic and sustainable agricultural management systems with low (1.90-2.01%) and moderate (2.10-2.40%) initial humus contents. Long-term field experiments with different agricultural management systems started in 1960 at the Lithuanian Research Centre for Agriculture and Forestry and soil humus dynamics experiments were conducted from 2006 to 2017. Results of the long-term use of organic and sustainable agricultural management systems with different crop rotations and fertilisation revealed the positive effect of the applied supplies on soil humus, especially for farmyard manure in combination with green manure. The incorporation of farmyard manure and biomass of white mustard resulted in a lower degree of humification when compared to green manure alone, green manure + mineral N, and farmyard and green manure + mineral N. In the low humus content soil, the degree of humification under all agricultural management systems was significantly improved, on average by 0.9% compared to soil with a moderate humus content. Keywords: green manure, crop rotation, organic and sustainable agriculture, humus, humic and fulvic acids.