Quantifying the Contribution of Agroforestry Trees to Cereal Crop Productivity Through Resource Complementarity in Nigerian Parkland Systems

This study quantifies the contribution of parkland agroforestry trees to cereal crop productivity through resource complementarity mechanisms in Nigerian parkland farming systems, focusing on farmer-managed Faidherbia albida and Vitellaria paradoxa parklands in the Guinea-Sudan savanna transition. Parkland agroforestry systems are traditional farming landscapes across the West African savanna where indigenous trees are retained within farm fields. The mechanisms through which trees improve crop productivity, including nitrogen deposition, microclimate moderation, soil moisture effects, and root-level complementarity, require quantification to support evidence-based parkland management recommendations. This study uses isotopic tracing (N-15 natural abundance), micro-meteorological monitoring, soil moisture probes, and root exclusion tube methodology to separately quantify the contributions of nitrogen, water, and microclimate to crop yield advantages under Faidherbia and Vitellaria canopies compared to open field positions across 18 farms in Zamfara, Niger, and Kwara States. Findings reveal that nitrogen deposition from Faidherbia leaf litter accounts for 62 percent of the under-canopy crop yield advantage, contributing an estimated 28 kilograms of nitrogen per hectare per year within the canopy influence zone. Microclimate moderation accounts for 24 percent of the yield advantage through reduced heat stress and improved water use efficiency. Vitellaria shows stronger microclimate benefits but lower nitrogen contributions. The study contributes original resource complementarity quantification for Nigerian parkland agroforestry and recommends density optimisation management for each species based on the identified contribution mechanisms.

Keywords: parkland agroforestry, Faidherbia albida, resource complementarity, N-15 isotope, cereal productivity.