Revitalizing soil health for climate resilience in Africa: The need for high rates of carbon inputs

Enhancing soil health is critical to improve crop productivity, fertilizer use efficiency, and resilience to climate change impacts for smallholder farmers in Africa. Increasing the use of mineral fertilizers is critical for achieving higher crop yield and residue return. However, it is crucial to consider the simultaneous use of carbon (C)-rich organic materials alongside mineral fertilizers to support soil health and enhance fertilizer use efficiency. It is proposed that increasing mineral fertilizer use without a concurrent increase in C-rich organic materials may not enhance soil organic carbon (SOC) and soil health in the long term. When the labile pool of nutrients is increased through mineral fertilizer, it can reduce microbial C use efficiency, thereby hindering the formation and stabilization of SOC. This reduction in efficiency can cause a more significant proportion of the returned plant residues to be lost as CO₂ through microbial respiration rather than being incorporated into the SOC pool. However, this effect can be mitigated by the concurrent application of large amounts of organic amendments, such as compost, manure or biochar, which provide a balanced supply of nutrients and C substrates to support microbial activity and enhance SOC formation.