Assessing the Potential of Biochar as a Viable Alternative to Synthetic Fertilizers in Sub-Saharan Africa Smallholder Farming: A Review

The adverse effects of long-term usage of synthetic fertilizers such as eutrophication, weed infestation, opportunistic diseases, and declining yields have been established. However, the fact that soil fertility declines because of continuous cropping to meet the demand for feeding the ever-growing population, coupled with the high cost of chemical fertilizers, has left little option. This mainly affects resource-poor smallholder farmers, who heavily depend on their production for sustenance and economic well-being. Current research efforts have underscored the urgency of mitigating this trend by seeking a cost-effective and eco-friendly alternative to avert impending global food crises. Biochar has gained attention as a possible alternative to meet the soil requirements on many fronts, such as improving soil functioning and restoring degraded lands. Biochar is also known to reduce heavy metal mobility and inorganic contaminants, mitigating salinity and drought stress as well as greenhouse gas emissions associated with agriculture. However, these studies need to be harmonized to draft a more pragmatic approach to policy formulation and establish an enhanced paradigm. In this paper, we review several studies on biochar and synthesize its possible use as an alternative or supplement to synthetic fertilizers to enhance crop productivity under standard and stressful growing conditions. The ability of biochar to sequester carbon and its impact on soil properties are highlighted. We emphasize its potential for soil nutrient management and the possibility of adopting it as an alternative to synthetic fertilizer in smallholder farming. We also point out several critical research gaps that call for attention and serve as pointers for future research.