Humus ndi chinthu chamtundu wakuda, amorphous, polydispersed organic chokhala ndi molekyulu yolemera kwambiri yomwe imakhala yovuta kwambiri. Amapangidwa kuchokera ku kuwonongeka kwa thupi, mankhwala, ndi tizilombo tating'onoting'ono ndi kusintha kwa zotsalira za nyama ndi zomera. Chifukwa chake, imakhala yochulukirapo m'nthaka, peat, lignite, madzi ndi sediment. Zomwe zimagwira ntchito mu humus ndi humic acid ndi fulvic acid, ndipo zimakhala ndi humin pang'ono. Popeza kuti humic acid imasungunuka mu alkali koma osati mu asidi, fulvic acid imasungunuka mu asidi ndi alkali, ndipo humus sasungunuka mu asidi ndi alkali, ndipo HM sisungunuka mu asidi ndi alkali. , kotero iwo akhoza kulekanitsidwa ndi kuyeretsedwa kumlingo wakutiwakuti kupyolera mu kusungunuka. Humic acid ndi macromolecular organic acid wopangidwa ndi magulu onunkhira komanso osiyanasiyana ogwira ntchito. Ili ndi reactivity yapamwamba ndipo imagwiritsidwa ntchito kwambiri muulimi, mankhwala ndi kuteteza zachilengedwe ndi zina.