SOIL QUALITY ASSESSMENT OF AN EXPERIMENTAL PLOT AT UNIVERSITY OF IBADAN, NIGERIA

This study aimed to describe, classify, and provide baseline data for assessing soil quality at the Organo Mineral Fertilizer Plant experimental plot, Barth Road, University of Ibadan. Objectives included evaluating the soils for agricultural use, mapping their spatial distribution, and determining soil quality ratings of the identified units.

A detailed soil survey was conducted on the 1.05 ha plot using a rigid grid method. Auger examinations at 10 m intervals revealed three mapping units, with one profile pit excavated in each. Soil samples from various horizons were air-dried, crushed, and sieved before undergoing physical, chemical, and biological analyses.

Three soil series were identified: Balogun (Typic Kanhaplausalf/Haplic Lixisol), Egbeda (Chromic Kandiustalf/Chromic Lixisol), and Ibadan (Typic Kandiustalf/Manganiferric Lixisol). Textures ranged from sandy to sandy clay loam. The Balogun series graded from sandy at the surface to sandy loam beneath. Soil pH values (6.20–7.07) indicated slight acidity to near-neutrality. Organic carbon content was moderate to high, with the Ibadan series recording the highest value (17.56 g/kg). Total nitrogen was moderate (4.38–6.32 g/kg). Although calcium, magnesium, potassium, and sodium were low, micronutrients such as manganese, iron, copper, and zinc were abundant.

All soils showed high base saturation (>50%) and well-developed horizons, confirming their classification as Alfisols. They were slightly acidic to slightly alkaline, with medium to high organic carbon levels, making them suitable for crop production. Based on the soil quality index, IND_B and IND_A performed best (1.00 and 0.90, respectively), while IND_C (SQI < 0.90) remained suitable for farming. To enhance productivity, exchangeable bases should be supplemented through organic and inorganic fertilizers. Overall, the soils are suitable for sustainable agricultural management and productivity improvement.