Humus Soil ecology 2 Sustainable agriculture 2 Carbon 1 Carbon sequestration 1 Chemical composition 1 Cycling 1 Fertilizers and other Amendments 1 Humic acid content 1 Litter (plant) 1 Manures 1 Nitrogen 1 Nutrient availability 1 Organic matter 1 Plant litter 1 Plant residues 1 Rhizosphere 1 Soil Biology 1 Soil Chemistry and Mineralogy 1 Soil Fertility 1 Soil amendments 1 Soil biology 1 Soil chemistry 1 Soil fauna 1 Soil fertility 1 Soil flora 1 Soil management 1 Soil moisture 1 Soil organic matter 1 Soils 1