Biological nitrogen enriched biochar enhances maize productivity, soil fertility and pest management in the humid tropical zone of Buea and the sub humid western highlands of Mbouda, Cameroon

Integrated sustainable crop productivity and pest management remain a pervasive modern-day agricultural challenge. The deployment of conventional approaches has jeopardised environmental sustainability with adverse effects including loss of long-term soil and plant productivity necessitating sustainable alternatives. Biological Nitrogen Enriched Biochar (BioNBiochar), a unique constituent of biochar and black soldier fly frass (BSF), offers an eco-friendly alternative to enhance maize yield and mitigate pest infestations across agroecological zones (AEZ) in Cameroon. The randomized complete block design field trials conducted across humid tropical (Buea) and sub-humid (Mbouda) AEZs investigated the effect of treatments: BioNBiochar, BSF frass, NPK, Poultry manure and control on soil fertility, maize yield and pest dynamics. Across the two AEZs, BioNBiochar consistently outperformed BSF frass, poultry manure, NPK fertiliser and the control, exhibiting significantly higher organic carbon (OC) (4.3%), soil pH, total nitrogen, exchangeable potassium and available phosphorus than all other treatments. OC also varied with agroecological zone, being significantly higher in Buea (3.5%) than in Mbouda (3.1%), and the AEZ × treatment interaction was significant, with the highest OC observed for the Buea × BioNBiochar combination. Maize yield was significantly higher under BioNBiochar (7.3 t/ha) than under all other treatments across both AEZs, with the lowest yield observed under the control (4.5 t/ha); yield also differed modestly by AEZ, being higher in Mbouda (5.8 t/ha) than in Buea (5.6 t/ha). Fall armyworm and stem borer infestation and their combined damage severity were lowest on plots amended with BioNBiochar and highest in the control across both AEZs, while pest pressure was somewhat greater in Mbouda than in Buea (fall armyworm: 2/plant; stem borer: 2/plant; damage severity: 3.6). The consistent performance of BioNBiochar across contrasting agroecological environments and better than other treatments demonstrates its potential as a sustainable soil amendment for promoting integrated pest management (IPM) and resilience in agroecosystems.