Plant-Soil Feedback Mechanisms and Their Role in Shaping Crop Rotation Outcomes in Nigerian Farming Systems

This study investigates plant-soil feedback mechanisms and their contribution to determining crop rotation productivity outcomes in Nigerian farming systems, developing an original theoretical integration of plant-soil feedbacks with rotation agronomy. Plant-soil feedbacks, in which plants modify soil biotic and abiotic properties that subsequently affect the performance of the same or different plant species, are fundamental ecological mechanisms that shape community composition in natural ecosystems. Their role in determining the benefits and drawbacks of crop rotation sequences has been insufficiently explored in tropical smallholder contexts, despite having major theoretical and practical implications for rotation system design. This study uses a split-field rotation trial design at sites in Ogun, Niger, and Kano States, establishing rotation sequences that include maize, cowpea, sorghum, groundnut, and cassava in various two-year combinations. Soil biotic properties including nematode community composition, pathogenic and beneficial fungal communities, root enzyme activity, and bacterial community structure are measured after each rotation phase. Plant performance is assessed for each crop following each rotation predecessor, and the strength of plant-soil feedback effects is quantified by regressing performance against soil biotic property changes. Findings reveal significantly positive plant-soil feedbacks in all cereal-legume rotation sequences, driven by legume-induced suppression of cereal pathogens and enhancement of nitrogen-cycling bacteria. Negative feedbacks accumulate under continuous monoculture of all tested crops within two seasons. The strength of feedback effects is strongly dependent on soil organic carbon, with high-SOC soils showing more stable rotation benefits. The study contributes an original plant-soil feedback framework for Nigerian rotation agronomy and recommends its integration into rotation system design extension guidance.

Keywords: plant-soil feedback, crop rotation, soil biota, Nigeria, rotation agronomy.