Short-Term Effects of Boiler Ash on Soil Microbial Population, Organic Carbon, Nitrogen Mineralization and Cowpea Biomass

Recycling boiler ash through the soil given their neutralizing capacity and phyto nutrient
concentrations can also result in deterioration of soil quality parameters such as soil microbial
biomass, communities, organic carbon and nitrogen mineralization, which in turn affects crop health,
productivity, and soil sustainable productivity. The objective of this study was to assess modifications
in soil pH, soil electrical conductivity, soil microbial population, organic carbon, nitrogen
mineralization, and cowpea performance at 30, 60, and 90 days after planting in boiler ash (BA)
alone, mixtures of BA with soil and poultry dropping (PM). The experiment was a completely
randomized design conducted in a screen house for 90 days. The result shows that following a 30, 60
and 90 days’ incorporation period, BA alone or in mixtures with soil or PM significantly (p<0.5)
increased soil pH and microbial activity but inhibit fungal growth and had little effect on cowpea
biomass growth. The concentration of total organic carbon and NH4-N increased but NO3-N
decreased relative to the un-amended soil. The effects were however found to be time and mixture
ratio-specific. These results demonstrate that with proper selection of application rates, amendment of
soils with BA may increase soil carbon, improve nitrogen mineralization and crop productivity and has
the potentials to inhibit pathogenic fungi but unlikely to disrupt other microbiological processes in soil
environments. Based on the conducted trial it can be stated that dumped boiler ash (100% BA)
stabilize overtime and improved soil pH, microbial population, organic carbon and nitrogen
mineralization. When mixed with soil or poultry droppings, organic C and N, N-supplying power (N
mineralization), pH and microbial population in soil also increased, but the magnitude of increase
varied with ratio of mixture. Our findings suggest enormous potential for the use of cowpea to reclaim
abandoned ash ponds for agriculture and that soil quality and fertility can be improved with boiler ash.