Assessment and Improvement of Soil Sampling and Analysis Procedures in Nigerian Agricultural Development Programmes

This study assesses the quality of soil sampling and analytical procedures used by Nigerian Agricultural Development Programmes (ADPs) and proposes standardised improvements applicable across geopolitical zones. Soil testing is the foundation of rational fertiliser recommendation, yet the procedures used by ADPs for sampling, preparation, and laboratory analysis vary significantly across states, generating inaccurate diagnoses and misaligned fertiliser recommendations that waste resources and underperform. Using a professional quality audit design, soil sampling protocols, sample preparation procedures, and laboratory methods were reviewed and field-assessed across ADP soil testing units in Kebbi (North West), Plateau (North Central), Kogi (North Central), Ekiti (South West), and Akwa Ibom (South South) States. A standardised set of 30 reference soil samples of known composition were submitted to each ADP laboratory as blind duplicates to assess analytical accuracy and inter-laboratory reproducibility. Laboratory equipment condition, staffing qualifications, and quality control systems were inspected. Findings revealed major inconsistencies in sampling Soil Scienceh, composite sampling procedures, and analytical methods for pH, phosphorus, and potassium across the five ADP laboratories. Analytical accuracy ranged from 62 to 91 percent for pH but dropped to 44 to 68 percent for available phosphorus, indicating unacceptably high error rates for fertiliser recommendation use. The study delivers a standardised ADP Soil Testing Quality Manual with recommended procedures, inter-laboratory calibration protocols, and minimum staffing and equipment standards for implementation by the Federal Ministry of Agriculture. Keywords: soil sampling, agricultural development programme, soil testing quality, fertiliser recommendation, Nigeria.