A composted soil conditioner is produced from the slaughter wastes of pasture fed stock and the untreated bark of largely one species of tree (Pinus radiata) by an aerobic thermophilic composting process. It is very consistent in composition, disinfected to EPA standards and non-toxic to plant growth when fully matured. In-process quality control ensures the composting process is maintained under optimum conditions. The composted soil conditioner has found a wide variety of uses to date. It has many of the physical properties of peat, with good water holding capacity and the ability to aerate heavy soils. As an agricultural by-product being recycled back to the land in a stabilized form, composting has provided a convenient means of recovering a resource that otherwise would be lost.