Effect of incubation temperatures and different sources of N and P on decomposition of sawdust in soil

Abstract

Sawdust from Canarium schweinfurthii (Engl.) treated with diary manure, liquid NH 3 and H 3PO 4 was added to soils and incubated for 13 weeks over a range of temperatures from 25 to 40°C. The results obtained necessitated the setting up of a related study in which dairy manure, aqueous NH 3 or urea and H 3PO 4 or water-soluble P 2O 5 were used to treat the sawdust before addition to soils and later incubated at 30°C. The results indicate that the rate of C mineralization increased with temperature from 25 to 40°C with the optimum between 30 and 35°C. The lowering of the C:N ratio of sawdust to 12:1 with inorganic N while maintaining a neutral reaction enhanced decomposition of the treated over the untreated sawdust at 25°C. After 13 weeks of incubation, there was no significant difference in the effectiveness of either aqueous NH 3 or urea and H 3PO 4 or water-soluble P 2O 5 in promoting C mineralization. There was also no need for supplemental P in enhancing the rate of C mineralization in sawdust.