Abstract

In Southwestern Nigeria (SWN), the high demand for maize has resulted in increased levels of maize cultivation. However, continuous maize cultivation is directly or indirectly affecting soil nutrient reserves. This study therefore assessed and compared the soil physical conditions, chemical contents, and rhizobacterial loads of soil samples collected in maize fields across the five (Guinea Savannah-GS, Derived Savannah-DS, Lowland Rainforest-LR, Freshwater Swampy Forest-FW, and Mangrove Forest-MF) ecological zones (EZs) of SWN. Three (GS, DS, and FW) of the five EZs were sandy-loam soil. The soil pH, moisture content, and rhizobacterial loads fall within the agronomic standard but were observed to be weakly correlated when compared across the EZs. Available phosphorus, magnesium, manganese, iron, zinc, and copper varied from moderate to high across the five EZs. Soil organic carbon, nitrogen, potassium, calcium, and sodium were generally low in all the EZs. Of interest, the rhizobacterial loads depend on the soil's physical properties and chemical contents across the EZs. The study therefore uncovered that the soil nutrient reserves in maize fields in SWN vary and more favourably in savannah areas than swampy areas. Although some of the soils in SWN are fertile, the rhizobacterial loads of LR, FW, and MF are low. As a result of this, farmer’s awareness of best agricultural practices that will help improve soil fertility and nutrient status towards sustainable maize production in SWN should be prioritized.

Key words: Soil nutrient, maize, soil fertility, plant growth promoting rhizobacteria (PGPR), soil properties, soil biomass.