Soil Quality Assessment for Urban Agriculture in Two Cities of Southwest Nigeria Adelana A.O.

Abstract

Urban agriculture (UA) is increasingly becoming vital for food security and
sustainable urban development, yet urban soils often face challenges like
compaction, nutrient depletion, and poor soil structure. This study was carried out
to assess soil quality across 12 UA sites in Akure and Okitipupa, southwest
Nigeria, evaluating physical, chemical, and biological properties in order to guide
management strategies. Soil samples were analyzed for texture, bulk density (BD),
hydraulic conductivity (Ks), water-stable aggregates (WSA), pH, organic carbon
(Corg), total nitrogen (Ntot), available phosphorus (AvP), exchangeable cations,
microbial biomass carbon (Cmic), nitrogen (Nmic), and soil microbial respiration
(SMR). Results showed that Akure soils were sandy loam, slightly acidic (pH
5.91–6.76), with variable Corg (6.05–19.65 g kg-1) and low Ntot (0.73–3.63 g kg-1).
Okitipupa soils were loamy sand to sandy loam, moderately acidic (pH 4.93–5.96),
with higher Corg (8.76–22.71 g kg-1). Principal component analysis (PCA) revealed
that the first two components explained 75.4% of the variance, with PC1 driven by
texture and Ks, and PC2 by Corg, Ntot, and AvP. Hierarchical clustering grouped the
UA sites into four clusters: Cluster 1 (sandy, acidic, nutrient-poor), Cluster 2
(compacted, poor soil structure), Cluster 3 (fertile, loamy, high Corg/Ntot), and
Cluster 4 (moderate fertility, erosion-prone). Management recommendations
include organic amendments and cover crops for Cluster 1, deep tillage and raised
beds for Cluster 2, crop rotation and minimal tillage for Cluster 3, and mulching
with conservation tillage for Cluster 4. These results highlight urban soil
heterogeneity and provide tailored strategies to enhance agricultural productivity
in southwest Nigeria.
Nigeria.