Simulation study to assess the potential of selected agro-organic wastes for ability to reduce N volatilization from cow manure

Abstract

Six agro-organic wastes were evaluated for their ability to reduce N losses from cattle manure during storage. The materials were selected based on their low pH, high C: N ratios or high cation exchange capacity. They included; filter mud (FM), sawdust (SD), a common by-product of the timber industry, maize stover (MS), wood ash (WA), Ondiri peat (OP), and coffee pulp (CP), a waste product from coffee factories. Manure samples equivalent to 40 g (dry weight basis) were combined with 20% of each of the amendments and placed in 500 ml elernmeyer flasks. Volatilization of ammonia was determined using a laboratory gas train simulator and volatilized NH3 was collected in 100 ml of 2% boric acid and determined by titration with 0.01 M H2SO4. Mixing organic amendments with manure significantly reduced NH3 losses relative to nonamended manure heaps with the exception where wood ash was added. The total N content of the untreated manure prior to incubation was 17.11 g N kg-1 and after 51 days declined to 9.36 g N kg-1 which translated to a 43% loss from the initial levels. The cumulative NH3 losses ranged between 7.6% to 78.7% of the initial N, depending on the type of amendment. The N losses were positively correlated (r2=0.855) to the initial pH of the amended manures. Addition of sawdust, resulted in least mass and carbon loss and the original mixture was unchanged showing that minimal decomposition had occurred.