Decomposition of Potato Processing Wastes in Soil'

Solid filtered or centrifuged potato processing wastes were obtained from three potato processors in Idaho. The waste samples were dried and ground to pass a 2-nun sieve and added to soils at rates of 0, 2.5, 10, and 25 g/kg. The 100-g samples of Portneuf silt loam soil containing the waste material was incubated at 26 °C and decomposition of the added wastes was determined by measuring CO, evolution in a flowing air stream passing over the soil in the incubation flask. Each increment of added organic waste material increased the amount of carbon evolved during the 12-week incubation. The waste materials contained 6.8, 20.4, or 65.5 g N/kg waste. However, these differences in N did not change the amount of CO, evolved at the 12-week incubation, although the evolution curves were shaped somewhat differently during the 12 weeks. Regression analyses of the cumulative carbon resulted in highly significant values being obtained for each potato processing waste material. Decomposition of the solid waste materials ranged from 24 to 92% depending upon the source and application rate. The rapid decomposition of the solid wastes verified field research indicating that potato wastes have not more than 1 yr residual fertilizer value. The organic waste is not likely to accumulate in the