Evaluation of Wood Ash as Additive for Cow Manure Composting

This study was conducted to produce high-quality compost using both cow manure and wood ash that can specifically be used to increase the fertility of soils in tropical regions. Increased proportions of wood ash were co-composted with cow manure. During composting, the composts produced presented the classical composting temperature curve and attain a thermophilic composting phase (about 60 oC). After 117 days of composting, the produced composts (CMA 0%; CMA 5%; CMA 10% and CMA15%) had a C/N ratio between 16 and 30, and their pH, was basic, indicating maturity. They were rich in minerals (Mg; Ca; K+; and Na+) and poor in heavy metals (Zn; Cu and Pb). Wood ash addition raise the fungal communities except for CMA 0% and did not impair significantly on bacteria communities; however, addition of high amounts of wood ash could reduce the metabolism of the microbial communities including cellulase activity that showed a proportional decrease according to the added amount except for CMA 15%. The composts showed a germination index greater than 80% at all concentrations, indicating the absence of phytotoxicity. Therefore, co-composting of cow manure with wood ash (<15%) allowed to obtain a good organic fertilizer with higher liming potential, nutrient content, and less hazardous material which could be used in farms to remediate acidity of tropical soils.