Developing an Original Methodology for Multi-Scale Soil Health Assessment in Nigerian Agricultural Landscapes

Soil health assessment in Nigeria is limited by the lack of a standardised, multi-scale methodology that can be applied across diverse agroecological zones and farming system types while remaining affordable and practically implementable by both research and extension institutions. This study developed an original multi-scale soil health assessment methodology for Nigerian agricultural landscapes. A methodology development approach integrating indicator selection theory, indicator validation, and field application testing across three agroecological zones was employed. Phase one reviewed 78 published soil health assessment frameworks to identify common indicators and spatial scale considerations. Phase two conducted empirical testing of 32 candidate indicators (physical, chemical, and biological) across 90 soil profiles representing the Sudan savanna (Kano State), Guinea savanna (Kwara State), and humid forest (Anambra State) zones. Principal component analysis identified the minimum data set of 10 indicators that captured 87 percent of the variability explained by the full 32-indicator set. Phase three developed standardised field measurement protocols for all 10 minimum data set indicators, including protocol adaptations for low-resource measurement using affordable field test kits. The resulting Multi-Scale Soil Health Assessment Methodology (MSHAM-Nigeria) provides separate indicator weighting coefficients for each of the three zones, reflecting the different soil health constraints characteristic of each ecology. Validation against crop yield data across 60 farms showed that the MSHAM-Nigeria soil health composite score explained 61 percent of yield variation. Expert review by 20 soil scientists confirmed the methodology's original contribution.

Keywords: soil health assessment, multi-scale methodology, Nigerian agroecological zones, minimum data set, original methodology