1) Biological process 2) Organic process 3) The formation of humus 
Process during the formation of humus; see there. Humus Term (Latin for soil) for the entirety of the almost exclusively dead organic matter of a soil, which makes up the vast majority of the soil organic matter (OBS or SOM = Soil Organic Matter). However, about 5% of the OBS also consists of living organic matter, i.e. all living animal (such...
the formation of humus.